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rfc:rfc3651

Network Working Group S. Sun Request for Comments: 3651 S. Reilly Category: Informational L. Lannom

                                                                  CNRI
                                                         November 2003
          Handle System Namespace and Service Definition

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2003).  All Rights Reserved.

IESG Note

 Several groups within the IETF and IRTF have discussed the Handle
 System and it relationship to existing systems of identifiers.  The
 IESG wishes to point out that these discussions have not resulted in
 IETF consensus on the described Handle System nor on how it might fit
 into the IETF architecture for identifiers.  Though there has been
 discussion of handles as a form of URI, specifically as a URN, these
 documents describe an alternate view of how namespaces and
 identifiers might work on the Internet and include characterizations
 of existing systems which may not match the IETF consensus view.

Abstract

 The Handle System is a general-purpose global name service that
 allows secured name resolution and administration over the public
 Internet.  This document provides a detailed description of the
 Handle System namespace, and its data, service, and operation models.
 The namespace definition specifies the handle syntax and its semantic
 structure.  The data model defines the data structures used by the
 Handle System protocol and any pre-defined data types for carrying
 out the handle service.  The service model provides definitions of
 various Handle System components and explains how they work together
 over the network.  Finally, the Handle System operation model
 describes its service operation in terms of messages transmitted
 between client and server, and the client authentication process
 based on the Handle System authentication protocol.

Sun, et al. Informational [Page 1] RFC 3651 Handle System Service Definition November 2003

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
 2.  Handle System Namespace. . . . . . . . . . . . . . . . . . . .  3
 3.  Handle System Data Model . . . . . . . . . . . . . . . . . . .  4
     3.1.  Handle Value Set . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Pre-defined Handle Data Types. . . . . . . . . . . . . .  9
           3.2.1.  Handle Administrator: HS_ADMIN . . . . . . . . . 10
           3.2.2.  Service Site Information: HS_SITE. . . . . . . . 14
           3.2.3.  Naming Authority Delegation Service:
                   HS_NA_DELEGATE . . . . . . . . . . . . . . . . . 19
           3.2.4.  Service Handle: HS_SERV. . . . . . . . . . . . . 20
           3.2.5.  Alias Handle: HS_ALIAS . . . . . . . . . . . . . 21
           3.2.6.  Primary Site: HS_PRIMARY . . . . . . . . . . . . 21
           3.2.7.  Handle Value List: HS_VLIST. . . . . . . . . . . 22
 4.  Handle System Service Model. . . . . . . . . . . . . . . . . . 22
     4.1.  Handle System Service Components . . . . . . . . . . . . 23
           4.1.1.  Global Handle Registry (GHR) . . . . . . . . . . 23
           4.1.2.  Local Handle Service (LHS) . . . . . . . . . . . 26
     4.2.  Handle System Middle-Ware Components . . . . . . . . . . 27
           4.2.1.  Handle System Caching Service. . . . . . . . . . 27
           4.2.2.  Handle System Proxy Server . . . . . . . . . . . 28
     4.3.  Handle System Client Components. . . . . . . . . . . . . 28
 5.  Handle System Operation Model. . . . . . . . . . . . . . . . . 29
     5.1.  Handle System Service Request and Response . . . . . . . 30
     5.2.  Handle System Authentication Protocol. . . . . . . . . . 32
 6.  Security Considerations. . . . . . . . . . . . . . . . . . . . 37
 7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 38
 8.  References and Bibliography. . . . . . . . . . . . . . . . . . 38
 9.  Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 40
 10. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 41

1. Introduction

 The Handle System manages handles as globally unique names for
 Internet resources.  It was originally conceived and described in a
 paper by Robert Kahn and Robert Wilensky [22] in 1995.  The Handle
 System provides a general-purpose global name service that allows
 handles to be resolved and administrated securely over the public
 Internet.  The Handle System categorizes its service into two
 categories: the handle resolution service and the handle
 administration service.  Clients use handle resolution service to
 resolve handles into their values.  The handle administration service
 deals with client requests to manage these handles, including adding
 and deleting handles, and updating handle values.
 The document "Handle System Overview" [1] provides an architectural
 overview of the Handle System, and its relationship to other Internet
 services such as DNS [2,3] and LDAP[4].  This document provides a

Sun, et al. Informational [Page 2] RFC 3651 Handle System Service Definition November 2003

 detailed description of the Handle System namespace, its data and
 service model, and its operation model.  It assumes that readers are
 familiar with the basic concepts of the Handle System as described in
 the overview document.
 The namespace definition specifies the handle syntax and its semantic
 structure.  The data model defines the data structures used by the
 Handle System protocol and any pre-defined data types for carrying
 out the handle service.  The service model provides definitions of
 various Handle System components and explains how they work together
 over the network.  Finally, the Handle System operation model
 describes its service operation in terms of messages transmitted
 between client and server, and the client authentication process
 based on the Handle System authentication protocol.

2. Handle System Namespace

 Handles are character strings that may consist of a wide range of
 characters.  Every handle in the Handle System consists of two parts:
 its naming authority, followed by a unique local name under the
 naming authority.  The naming authority and the local name are
 separated by the ASCII character "/" (octet 0x2F).  The following
 table provides the handle syntax definition in ABNF [5] notation:
     <Handle>          = <NamingAuthority> "/" <LocalName>
     <NamingAuthority> = *(<NamingAuthority>  ".") <NAsegment>
     <NAsegment>       = 1*(%x00-2D / %x30-3F / %x41-FF )
                       ; any octets that map to UTF-8 encoded
                       ; Unicode 2.0 characters except
                       ; octets '0x2E' and '0x2F' (which
                       ; correspond to the ASCII characters '.',
                       ; and '/').
     <LocalName>       = *(%x00-FF)
                       ; any octets that map to UTF-8 encoded
                       ; Unicode 2.0 characters
                     Table 2.1: Handle syntax
 As shown in Table 2.1, both <NamingAuthority> and <LocalName> are
 UTF-8 [6] encoded character strings.  The Handle System protocol
 mandates UTF-8 encoding for handles transferred over the wire.  The
 <LocalName> may consist of any characters from the Unicode 2.0
 standard [7].  The <NamingAuthority> may use any characters from the
 Unicode 2.0 standard except the ASCII character '/' (0x2F), which is

Sun, et al. Informational [Page 3] RFC 3651 Handle System Service Definition November 2003

 reserved to separate the <NamingAuthority> from the <LocalName>.  A
 <NamingAuthority> may consist of multiple non-empty <NAsegment>s,
 each of which separated by the ASCII character '.' (octet 0x2E).
 Naming authorities are defined in a hierarchical fashion resembling a
 tree structure.  Each node and leaf of the tree is given a label that
 corresponds to a naming authority segment (<NAsegment>).  The parent
 node represents the parent naming authority.  Naming authorities are
 constructed left to right, concatenating the labels from the root of
 the tree to the node that represents the naming authority.  Each
 label (or its <NAsegment>) is separated by the character '.' (octet
 0x2E).  For example, the naming authority for the Digital Object
 Identifier (DOI) project is "10".  It is a root-level naming
 authority as it has no parent naming authority for itself.  It can,
 however, have many child naming authorities.  For example, "10.1045"
 is a child naming authority of "10" for the D-Lib Magazine.
 By default, handles are case sensitive.  However, a handle service,
 global or local, may implement its namespace so that ASCII characters
 under the namespace are treated as case insensitive.  For example,
 the global handle service, formally known as the Global Handle
 Registry (GHR), is implemented such that ASCII characters are treated
 as case insensitive.  Since the GHR manages all handles for naming
 authorities, ASCII characters in naming authorities are treated as
 case insensitive.

3. Handle System Data Model

 The Handle System provides a name-to-value binding service over the
 public Internet.  Each handle may have a set of values assigned to
 it.  The Handle System maintains the value set of each handle and
 will return it in response to any handle resolution request.  The
 Handle System data model defines the conceptual data structure for
 these values.  The data model used by the protocol may not be the
 exact physical data model used for storage in any specific
 implementation.  Rather, it is the data model followed by the Handle
 System protocol as specified in the "Handle System Protocol
 Specification" [8].

3.1. Handle Value Set

 Each handle may have a set of values assigned to it.  These handle
 values use a common data structure for its data.  For example, each
 handle value has a unique index number that distinguishes it from
 other values in the value set.  It also has a specific data type that
 defines the syntax and semantics of the data in its data field.
 Besides these, each handle value contains a set of administrative
 information such as TTL and permissions.  Figure 3.1 shows the handle

Sun, et al. Informational [Page 4] RFC 3651 Handle System Service Definition November 2003

 "10.1045/may99-payette" with a set of three handle values.  One of
 these values (with index number set to 1) is shown in detail.  (Note
 that the encoding of the length for each field is not shown in Figure
 3.1.  Also, the empty <reference> field consists of a 4-byte integer
 whose value is zero.)
                 Handle "10.1045/may99-payette"
                              |
                              |
                              V
  1. ————————————————————

| <index>: 3 |

  1. ———————————————————— |

| <index>: 2 | |

  1. ———————————————————— | |

| | | |

 |  <index>:           1                                       | | |
 |  <type>:            URL                                     | | |
 |  <data>:            http://www.dlib.org/dlib...             | | |
 |  <TTL>:             {Relative: 24 hours}                    | | |
 |  <permission>:      PUBLIC_READ, ADMIN_WRITE                | | |
 |  <timestamp>:       927314334000                            | | |
 |  <reference>:       {empty}                                 | |-
 |                                                             |-
  -------------------------------------------------------------
   Figure 3.1: Handle "10.1045/may99-payette" and its set of values
 In Figure 3.1, it shows a handle value whose its index is set to 1.
 The data type for the handle value is URL.  The URL data as stated in
 the <data> field is "http://www.dlib.org/dlib...".  The TTL (time to
 live) entry suggests that the value record should be cached no more
 than 24 hours before the source of the information to be consulted
 again.  The <permission> field grants anyone permission to read, but
 only the administrator to update the value.  The <reference> field is
 empty.  It may contain a list of references to other handle values as
 credentials for this handle value.
 Thus a handle value may be thought of as a record that consists of a
 group of data fields.  Each of these data fields is defined as
 follows:
    <index>
    An unsigned 32-bit integer that uniquely identifies a handle value
    from other handle values.

Sun, et al. Informational [Page 5] RFC 3651 Handle System Service Definition November 2003

    <type>
    A UTF8-string that identifies the data type for the value record.
    Note that throughout this document, a UTF8-string is defined as a
    data structure that consists of a 4-byte unsigned integer followed
    by an UTF-8 encoded character string.  The integer specifies the
    number of octets in the character string.
    The <type> field identifies the data type that defines the syntax
    and semantics of data in the next <data> field.  The data type may
    be registered with the Handle System to avoid potential conflicts.
    The Handle System has a reserved naming authority "0.TYPE" for
    registered data types.  For example, "URL" (as shown in Figure
    3.1) is a registered data type.  It is registered as the handle
    "0.TYPE/URL".  The handle may have a value that explains the
    syntax and semantics of the data type.
    Data types under the Handle System may be hierarchical.  Each
    level of the hierarchy may be named in terms of a UTF8-String with
    no '.' (0x2E) characters.  The '.' character is used to mark the
    boundary between hierarchy levels.  For example, the Handle System
    data type "a.b" may be considered as a sub-type "b" under the type
    "a".  Similarly, handle values of <type> "a.b.x", "a.b.y" and
    "a.b.z" may be considered as handle values under the common type
    hierarchy "a.b".
    For any handle values, the UTF8-string in the <type> field may not
    end with the '.' character.  In other words, no Handle System data
    type should end with the '.' character.  However, the '.'
    character may appear in the end of the <type> parameter in a
    handle query.  This is used to query for all handle values under a
    common type hierarchy.  For example, one may query for all handle
    values under the type hierarchy "a.b" (e.g., handle values of
    <type> "a.b.x", "a.b.y" and "a.b.z") by setting the <type>
    parameter to "a.b.".  Note here that the <type> parameter ends
    with the '.' character.  Details of the handle query operation can
    be found in the Handle System protocol specification [8].
    <data>
    A sequence of octets (preceded by its length in a 4-byte unsigned
    integer) that describes the resource identified by the handle. The
    syntax and semantics of these octets are identified by the <type>
    field.
    <permission>
    An eight-bit bit-mask for access control of the handle value.
    Access control is defined in terms of read, write, and execute

Sun, et al. Informational [Page 6] RFC 3651 Handle System Service Definition November 2003

    permissions, applicable to either general public or handle
    administrator(s).  Each handle value can have its permission field
    specified as any combination of the following bits:
      PUBLIC_WRITE   (0x01)     permission that allows anyone to
                                modify or delete the handle value.
      PUBLIC_READ    (0x02)     permission that allows anyone to read
                                the handle value.
      ADMIN_WRITE    (0x04)     permission that allows any handle
                                administrator to update or delete the
                                handle value.
      ADMIN_READ     (0x08)_    permission that allows the handle
                                value to be read by any handle
                                administrator with AUTHORITIVE_READ
                                privilege.
      PUBLIC_EXECUTE (0x10)     permission that allows anyone to
                                execute the program identified by the
                                handle value on the handle host as
                                anonymous user.  Because of the
                                security risks this may have brought
                                up, implementations may choose not to
                                support such permission, or provide
                                options so that it can be disabled at
                                deployment.
      ADMIN_EXECUTE  (0x20)     permission that allows handle
                                administrator(s) to run the program
                                identified by the handle value on the
                                handle server.  The handle server must
                                authenticate the handle administrator
                                before executing the program.  The
                                handle administrator must have an
                                established account on the handle
                                server.  The execution of the handle
                                value should assume the same privilege
                                as the one given to the account for
                                the handle administrator.  Because of
                                the security risks this may have
                                brought up, implementations may choose
                                not to support such permission, or
                                provide options so that it can be
                                disabled at deployment.

Sun, et al. Informational [Page 7] RFC 3651 Handle System Service Definition November 2003

    Note that a handle value with no PUBLIC_READ nor ADMIN_READ
    permission can not leave the handle server.  It may be used, for
    example, to store secret keys for authentication purposes.  A
    handle value with neither PUBLIC_WRITE nor ADMIN_WRITE permission
    makes the handle value immutable and cannot be deleted by any
    handle administrator (via the Handle System protocol).
    The administrator for a given handle must specify the permission
    for each handle value.  Implementations may choose PUBLIC_READ and
    ADMIN_WRITE as the default permission for each handle value.
    Handle servers must check permissions before fulfilling any client
    request.
    <TTL>
    An octet followed by a 4-byte integer that specifies the Time-To-
    Live of the value record.  It is used to describe how long the
    value record can be cached before the source of the information
    should again be consulted.  A zero value for a TTL indicates that
    the value record should only be used for the transaction in
    progress and should not be cached.  Any non-zero TTL is defined in
    terms of a TTL type (specified in the first octet), followed by
    the TTL value (the 32-bit unsigned integer that follows the TTL
    type).  The TTL type indicates whether the TTL value is absolute
    or relative.  The absolute TTL value defines the time to live in
    terms of seconds since 00:00:00 UTC, January 1st 1970.  A relative
    TTL specifies the time to live in terms of the number of seconds
    elapsed since the value was obtained by the client from any handle
    server.
    <timestamp>
    An 8-byte (long) integer that records the last time the value was
    updated at the server.  The field contains elapsed time since
    00:00:00 UTC, January 1970 in milliseconds.  The choice of
    milliseconds is to avoid potential collision when updating the
    value.
    <reference>
    A 4-byte integer followed by a list of references to other handle
    values.  The integer specifies the number of references in the
    list.  Each reference in the list refers to another handle value
    in terms of a UTF8-string and a 4-byte integer (where the UTF8-
    string is the handle name and the integer is the value index).
    References are generally used to add credentials to the current
    handle value.  For example, a handle value may make itself more
    trust-worthy by referring to a digital signature issued by a
    commonly trusted entity.

Sun, et al. Informational [Page 8] RFC 3651 Handle System Service Definition November 2003

 By default, the Handle System returns all the handle values with
 public-read permission in response of any resolution request.  It is
 possible for a client to ask for a subset of those values with
 specific data type (e.g., all URLs assigned to the handle).  The
 client may also ask for a specific handle value based on a specific
 value index.
 Each handle value can be uniquely referenced by the combination of
 the handle and its value index.  Care must be taken when changing the
 value index as it may break an existing reference to the handle
 value.  For example, suppose the handle X/Y has a value whose index
 is 1.  That value may be referred to as X/Y:1.  If the handle
 administrator changes the value index from 1 to 2, the reference to
 X/Y:1 will become obsolete.  Any reference to the handle value will
 have to change to X/Y:2.
 Value records assigned to any handle may or may not have continuous
 index numbers.  Nor can it be assumed that the index will start with
 0 or 1.  A handle administrator may assign a handle value with any
 index as long as each index is unique within the value set.
 A handle value may be "privatized" or "disabled" by setting its
 <permission> field as "authorized-read".  This limits read-access to
 the handle administrator only.  The "privatized" value can then be
 used to keep any historical data (on behalf of the handle
 administrator) without exposing it to public.  Such approach may also
 be used to keep any obsolete handle or naming authority from being
 reused accidentally.

3.2. Pre-defined Handle Data Types

 Every handle value must have a data type specified in its <type>
 field.  The Handle System provides a type registration service that
 allows organizations to register new data types for their
 applications.  Data types can be registered as handles under the
 naming authority "0.TYPE".  For example, the URL data type is
 registered under the Handle System as the handle "0.TYPE/URL".  The
 handle may have a handle value that refers to RFC1738 [9], an IETF
 standard document that defines the syntax and semantics of URL.
 The Handle System pre-defines a set of data types to carry out the
 handle service.  For example, HS_ADMIN is a pre-defined data type
 used to describe handle administrators or administrator groups.
 HS_SITE is a pre-defined data type to describe the service interface
 of any Handle System service component.  The following sections
 provide detailed descriptions of these pre-defined data types under
 the Handle System.

Sun, et al. Informational [Page 9] RFC 3651 Handle System Service Definition November 2003

3.2.1. Handle Administrator: HS_ADMIN

 Each handle has one or more administrators.  Any administrative
 operation (e.g., add, delete or modify handle values) can only be
 performed by the handle administrator with adequate privilege.
 Handle administrators are defined in terms of HS_ADMIN values.  Every
 handle must have at least one HS_ ADMIN value that defines its
 administrator.  Each HS_ADMIN value can be used to define a set of
 handle administrators sharing the same administration privilege.
 Handles with multiple administrators of different privileges may have
 multiple HS_ADMIN values.  HS_ADMIN values are used by the Handle
 System to authenticate handle administrators before fulfilling any
 handle administration request.
 Naming authorities, as described above, are themselves registered as
 handles under the reserved naming authority "0.NA".  These handles
 are referred to as naming authority handles.  Administrators for any
 naming authority are defined as the administrators of the
 corresponding naming authority handle.  For example, "0.NA/10" is the
 naming authority handle for the naming authority "10".  Hence any
 administrator for the naming authority handle "0.NA/10" is also the
 administrator for the naming authority "10".  Naming authority
 administrators are the only ones who can create handles or sub-
 naming authorities under the naming authority.  A sub-naming
 authority may define its own set of administrators to create handles
 or further levels of sub-naming authorities.  For example, the naming
 authority "10.1045" may have a totally different group of
 administrators from its parent naming authority "10".
 An HS_ADMIN value is a handle value whose <type> field is HS_ADMIN
 and whose <data> field consists of the following entries:
    <AdminRef>
    A reference to a handle value.  The reference consists of the
    handle name (a UTF8-string) followed by a 4-byte unsigned integer
    for the handle value index.  The handle value identifies the set
    of administrators for the handle.
    <AdminPermission>
    A 16-bit bit-mask that defines the administration privilege of the
    set of handle administrators identified by the HS_ADMIN value.
 The <AdminRef> entry refers to a handle value that can be used to
 authenticate the handle administrator.  Such handle value is called
 the handle administrator reference.  The handle administrator
 reference may contain the secret key, public key, or X.509
 certificate [10] provided by the handle administrator.  For example,
 the <AdminRef> entry may contain a handle administrator reference

Sun, et al. Informational [Page 10] RFC 3651 Handle System Service Definition November 2003

 whose <type> field is DSS_WITH_DES_CBC_SHA and whose <data> field
 contains a DES secret key [11], for use in the Cipher Block Chaining
 (CBC) mode of operation [12, 13].  The secret key can be used by the
 handle server to authenticate the handle administrator.  For stronger
 cryptographic algorithm, the handle administrator reference may
 contain a set of Triple-DES keys [23] and set its <type> to be DES-
 EDE3-WITH-CBC.
 A single handle may be assigned with both the HS_ADMIN value and the
 handle administrator reference.  In other words, the <AdminRef> entry
 may refer to a handle value assigned to the same handle that has the
 HS_ADMIN value.  In this case, authentication of the handle
 administrator does not rely on any other handles.  Alternatively, the
 handle administrator reference may be a handle value under a
 different handle.  Thus HS_ADMIN values from different handles may
 share a common handle administrator reference.  This feature allows
 sharing of handle administrators among different handles.  The handle
 administrator reference contains the secret key, public key, or X.509
 certificate provided by the administrator of these handles.
 Handle administrator reference may be of type HS_VLIST and has its
 <data> field contain a list of references to other handle values.
 Each of these handle values defines a handle administrator reference.
 The HS_VLIST value defines an administrator group.  Each handle
 administrator reference from the HS_VLIST is a member of the
 administrator group.  Each handle value reference is defined in terms
 of a <handle>:<index> pair.  An administrator group may also contain
 other administrator groups as its members.  This allows administrator
 groups to be defined in a hierarchical fashion.  Care must be taken,
 however, to avoid cyclic definition of administrators or
 administrator groups.  Multiple levels of administrator groups should
 be avoided due to their lack of efficiency, but will not be signaled
 as an error.  Client software should be prepared to detect any
 potential cyclic definition of administrators or <AdminRef> entries
 that point to non-existent handle values and treat them as an error.
 A handle can have multiple HS_ADMIN values, each of which defines a
 different handle administrator.  Different administrators can play
 different roles or be granted different permissions.  For example,
 the naming authority handle "0.NA/10" may have two administrators,
 one of which may only have permission to create new handles under the
 naming authority, while the other may have permission to create new
 sub-naming authorities (e.g., "10.1045").  The set of possible
 permissions for a handle administrator is defined as follows:
   Add_Handle (0x0001)
   This permission allows naming authority administrator to create new
   handles under a given naming authority.

Sun, et al. Informational [Page 11] RFC 3651 Handle System Service Definition November 2003

   Delete_Handle (0x0002)
   This permission allows naming authority administrator to delete
   handles under a given naming authority.
   Add_NA (0x0004)
   This permission allows the naming authority administrator to create
   new sub-naming authorities.
   Delete_NA (0x0008)
   This permission allows naming authority administrator to delete an
   existing sub-naming authority.
   Modify_Value (0x0010)
   This permission allows handle administrator to modify any handle
   values other than HS_ADMIN values.  HS_ADMIN values are used to
   define handle administrators and are managed by a different set of
   permissions.
   Delete_Value (0x0020)
   This permission allows handle administrator to delete any handle
   value other than the HS_ADMIN values.
   Add_Value (0x0040)
   This permission allows handle administrator to add handle values
   other than the HS_ADMIN values.
   Modify_Admin (0x0080)
   This permission allows handle administrator to modify HS_ADMIN
   values.
   Remove_Admin (0x0100)
   This permission allows handle administrator to remove HS_ADMIN
   values.
   Add_Admin (0x0200)
   This permission allows handle administrator to add new HS_ADMIN
   values.
   Authorized_Read (0x0400)
   This permission grants handle administrator read-access to handle
   values with the ADMIN_READ permission.  Administrators without this
   permission will not have access to handle values that require
   authentication for read access.
   LIST_Handle (0x0800)
   This permission allows naming authority administrator to list
   handles under a given naming authority.

Sun, et al. Informational [Page 12] RFC 3651 Handle System Service Definition November 2003

   LIST_NA (0x1000)
   This permission allows naming authority administrator to list
   immediate sub-naming authorities under a given naming authority.
 Administrator permissions are encoded in the <AdminPermission> entry
 in the <data> field of any HS_ADMIN value.  Each permission is
 encoded as a bit flag.  The permission is granted if the flag is set
 to 1, otherwise it is set to 0.
 Figure 3.2.1 shows an example of HS_ADMIN value that defines an
 administrator for the naming authority handle "0.NA/10".  In figure
 3.2.1, a naming authority administrator is identified by an HS_ADMIN
 value assigned to the naming authority handle "0.NA/10".  The
 administrator can be authenticated based on the handle value
 "0.NA/10":3, which is the handle value assigned to the naming
 authority handle "0.NA/10" and has its index set to 3.  The handle
 value "0.NA/10":3 may contain the secret or public key used by the
 administrator.  The administrator is granted permission to add,
 delete, or modify sub-naming authorities under "10", and add or
 delete handles directly under the naming authority.  The
 administrator may also add, delete, or modify any handle values
 assigned to the naming authority handle except those HS_ADMIN values.
 In other words, the administrator is not allowed to add, delete, or
 modify any administrators for the naming authority.
  1. ————————————————————
  2. ———————————————————— |
  3. ———————————————————— | |

| | | |

 |  <index>:       2                                           | | |
 |  <type>:        HS_ADMIN                                    | | |
 |  <data>:                                                    | | |
 |    <AdminRef>:    "0.NA/10": 3                              | | |
 |    <AdminPerm>:   Add_NA,     Delete_NA,                    | | |
 |                   Add Handle, Delete_Handle,                | | |
 |                   Add_Value,  Delete_Value,  Modify_Value,  | | |
 |                   Authorized_Read, List_Handle, List_NA     | | |
 |                                                             | | |
 |  <TTL>:         24 hours                                    | | |
 |  <permission>:  PUBLIC_READ, ADMIN_WRITE                    | | |
 |  <reference>:   {empty}                                     | |-
 |                                                             |-
  -------------------------------------------------------------
       Figure 3.2.1: Administrator for the naming authority
                     handle "0.NA/10"

Sun, et al. Informational [Page 13] RFC 3651 Handle System Service Definition November 2003

 HS_ADMIN values are used by handle servers to authenticate the handle
 administrator before fulfilling any administrative requests.  The
 server authenticates a client by checking whether the client has
 possession of the secret key (or the private key) that matches the
 one in any of the handle administrator references.  The
 authentication is carried out via the Handle System authentication
 protocol as described later in this document.
 HS_ADMIN values may require authentication for read access in order
 to prevent public exposure of the data.  Additionally, the handle
 administrator reference that contains the administrator's secret key
 should have neither PUBLIC_READ nor ADMIN_READ permission to prevent
 the key from leaving the server.

3.2.2. Service Site Information: HS_SITE

 The Handle System consists of a single distributed global handle
 service, also known as the Global Handle Registry (GHR), and
 unlimited number of Local Handle Services (LHSs).  Each handle
 service, global or local, may be replicated into multiple service
 sites.  Each service site may consist of multiple server computers.
 Service requests targeted at any handle service can be distributed
 into different service sites, and into different server computers
 within any service site.  Such architecture assures that each handle
 service could have the capacity to manage any large number of handles
 and handle requests.  It also provides ways for each handle service
 to avoid any single point of failure.
 Each handle service, global or local, may provide the same set of
 functions for resolving and administering its collection of handles.
 Handle services differ primarily in that each service is responsible
 for a distinct set of handles.  They are also likely to differ in the
 selection, number, and configuration of their components such as the
 servers used to provide handle resolution and administration.
 Different handle services may be created and managed by different
 organizations.  Each of them may have their own goals and policies.
 A service site typically consists of a cluster of server computers
 residing within a local Internet domain.  These computers work
 together to distribute the data storage and processing load at the
 site.  It is possible, although not recommended, to compose a site
 from servers at widely different locations.  Further, it is even
 possible to compose two different sites from the same set of servers.
 Each service site is defined by an HS_SITE value.  HS_SITE is a
 pre-defined Handle System data type.  An HS_SITE value defines a
 service site by identifying the server computers (e.g., IP addresses)
 that comprise the site along with their service configurations (e.g.,

Sun, et al. Informational [Page 14] RFC 3651 Handle System Service Definition November 2003

 port numbers).  HS_SITE values are typically assigned to naming
 authority handles.  The set of HS_SITE values assigned to a naming
 authority handle is called the service information for the naming
 authority.
 The service information is managed by the naming authority
 administrator.  It must reflect the configuration of the handle
 service for the naming authority.  Note that an additional layer of
 indirection, called a service handle, can be used to allow multiple
 naming authorities to reference a single set of HS_SITE values, as
 described later in this document (see section 3.2.3).  Clients of the
 Handle System depend on the service information to locate the
 responsible handle server before they can send their service
 requests.  The service information can also be used by clients to
 authenticate any service response from the handle server.
 An HS_SITE value is a handle value whose <type> field is HS_SITE and
 whose <data> field consists of the following entries:
   <Version>
   A 2-byte value that identifies the version number of the HS_SITE.
   The version number identifies the data format used by the HS_SITE
   value.  It is defined to allow backward compatibility over time.
   This document defines the HS_SITE with version number 0.
   <ProtocolVersion>
   A 2-byte integer value that identifies the handle protocol version.
   The higher byte of the value identifies the major version and the
   lower byte the minor version.  Details of the Handle System
   protocol is specified in [8].
   <SerialNumber>
   A 2-byte integer value that increases by 1 (and may wrap around
   through 0) each time the HS_SITE value gets changed.  It is used in
   the Handle System protocol to synchronize the HS_SITE values
   between client and server.
   <PrimaryMask>
   An 8-bit mask that identifies the primary site(s) of the handle
   service.  The first bit of the octet is the <MultiPrimary> bit.  It
   indicates whether the handle service has multiple primary sites.
   The second bit of the octet is the <PrimarySite> bit.  It indicates
   whether the HS_SITE value is a primary site.  A primary site is the
   one that supports administrative operations for its handles.  A
   <MultiPrimary> entry with zero value indicates that the handle
   service has a single primary site and all handle administration has
   to be done at that site.  A non-zero <MultiPrimary> entry indicates
   that the handle service has multiple primary sites.  Each primary

Sun, et al. Informational [Page 15] RFC 3651 Handle System Service Definition November 2003

   site may be used to administrate handles managed under the handle
   service.  Handles managed by such service may identify its primary
   sites using an HS_PRIMARY value, as described in section 3.2.5.
   <HashOption>
   An 8-bit octet that identifies the hash option used by the service
   site to distribute handles among its servers.  Valid options
   include HASH_BY_NA (0x00), HASH_BY_LOCAL (0x01), or HASH_BY_HANDLE
   (0x02).  These options indicate whether the hash operation should
   only be applied to the naming authority portion of the handle, or
   only the local name portion of the handle, or the entire handle,
   respectively.  The standard MD5 hashing algorithm [14] is used by
   each service site to distribute handles among its servers.
   <HashFilter>
   An UTF8-string entry reserved for future use.
   <AttributeList>
   A 4-byte integer followed by a list of UTF8-string pairs.  The
   integer indicates the number of UTF8-string pairs that follow.
   Each UTF8-string pair is an <attribute>:<value> pair.  They are
   used to add literal explanations of the service site.  For example,
   if the <attribute> is "Organization", the <value> should contain a
   description of the organization hosting the service site.  Other
   <attribute>s may be defined to help distinguish the service sites
   from each other.
   <NumOfServer>
   A 4-byte integer that defines the number of servers in the service
   site.  The entry is followed by a list of <ServerRecord>s.  Each
   <ServerRecord> defines a handle server that is part of the service
   site.  Each <ServerRecord> consists of the following data fields:
   <ServerRecord> ::= <ServerID>
                      <Address> <PublicKeyRecord> <ServiceInterface>
   where each field is defined as follows:
       <ServerID>
       A 4-byte unsigned integer that uniquely identifies a server
       process under the service site.  <ServerID>s do not have to
       begin with 1 and they don't have be consecutive numbers.  They
       are used to distinguish servers under a service site from each
       other.  Note that there can be multiple servers residing on any
       given computer, each with a different <ServerID>.

Sun, et al. Informational [Page 16] RFC 3651 Handle System Service Definition November 2003

       <Address>
       The 16-byte IPv6 [15, 16] address of the handle server.  Any
       IPv4 address should be presented as :::::FFFF:xxxx:xxxx (where
       xxxx:xxxx can be any 4-byte IPv4 address).
       <PublicKeyRecord>
       A 4-byte integer followed by a byte-array that contains the
       server's public key.  The integer specifies the size of the
       byte-array.  The byte-array (for the publickey) consists of
       three parts: a UTF8-string that describes the key type, a
       two-byte option field reserved for future use, and a byte-array
       that contains the public key itself.  For example, the UTF8-
       String "DSA_PUB_KEY" indicates that the <PublicKeyRecord>
       contains a DSA public key.  The storage format of the DSA key
       in the byte-array could then be found from the handle
       "0.type/DSA_PUB_KEY".  Public key in the <PublicKeyRecord> can
       be used to authenticate any service response from the handle
       server.
       The <PublicKeyRecord> may also contain an X.509 certificate.
       This happens if the key type field contains the UTF8-String
       "CERT.X509".  In this case, "CERT.X509" will map to the handle
       "0.TYPE/CERT.X509".  The handle may contain information that
       describes the syntax and semantics of the public key or its
       certificate.  Additional key type may also be registered (as
       handles under "0.TYPE") to further distinguish different kinds
       of X.509 certificates.  For example, "CERT.X509.DSA" may be
       used to denote X.509 certificates that contain DSA public keys.
       If the key type field of a <PublicKeyRecord> declares
       "CERT.X509.DSA", the <PublicKeyRecord> must contain a X.509
       certificate with a DSA public key in it."
       <ServiceInterface> ::=    <InterfaceCounter>
                               * [  <ServiceType>
                                    <TransmissionProtocol>
                                    <PortNumber>  ]
       A 4-byte integer followed by an array of triplets consisting of
       <ServiceType, TransmissionProtocol, PortNumber>.  The 4-byte
       integer specifies the number of triplets.  Each triplet lists a
       service interface provided by the handle server.  For each
       triplet, the <ServiceType> is an octet (as a bit mask) that
       specifies whether the interface is for handle resolution
       (0x01), handle administration (0x02), or both.  The
       <TransmissionProtocol> is also an octet (as a bit mask) that
       specifies the transmission protocol.  Possible transmission
       protocols include TCP (0x01), UDP (0x02), and HTTP (0x04).  The

Sun, et al. Informational [Page 17] RFC 3651 Handle System Service Definition November 2003

       <PortNumber> is a 4-byte unsigned integer that specifies the
       port number used by the interface.  The default port number is
       2641.
 Figure 3.2.2 shows an example of handle service site in terms of a
 HS_SITE value.  The HS_SITE value is assigned to the naming authority
 handle "0.NA/10".  The <PrimaryMask> indicates that it is the only
 primary site of the handle service.  The site consists of three
 handle servers, as indicated in the <NumOfServer>.  These servers
 provide handle resolution and administration service for every handle
 under the naming authority "10".  The first server record (ServerID
 0) shows two service interfaces, one for handle resolution and the
 other for handle administration.  Each interface has its own port.
 Each server within a service site is responsible for a subset of
 handles managed by the handle service.  Clients can find the
 responsible server by performing a common hash-operation.  The hash-
 operation will first convert all ASCII characters in the handle into
 upper-case.  It then applies the MD5 hashing upon the portion of the
 converted handle string (according to the <HashOption> entry).  The
 result is a 16-byte integer.  The absolute value of the integer will
 be divided by the number of servers (specified in the <NumOfServer>
 entry).  The remainder is the sequence number (starting with zero) of
 the <ServerRecord> listed in the HS_SITE value.  From the
 <ServerRecord>, clients can find the IP address of the handle server
 for their handle requests.

Sun, et al. Informational [Page 18] RFC 3651 Handle System Service Definition November 2003

  1. ———————————————————–
  2. ———————————————————– |
  3. ———————————————————- | |

| | | |

 | <index>:       2                                          | | |
 | <type>:        HS_SITE                                    | | |
 | <data>:                                                   | | |
 |    Version:           0                                   | | |
 |    ProtocolVersion:   2.1                                 | | |
 |    SerialNumber:      1                                   | | |
 |    PrimaryMask:                                           | | |
 |        MultiPrimary:    FALSE                             | | |
 |        PrimarySite:     TRUE                              | | |
 |    HashOption:        HASH_BY_HANDLE                      | | |
 |    HashFilter:        {empty UTF8-String}                 | | |
 |    AttributeList:     0    {followed by no attributes}    | | |
 |    NumOfServer:       3                                   | | |
 |         {followed by a list of <ServerRecord>}            | | |
 |                                                           | | |
 |         -----------------------------------------         | | |
 |       ------------------------------------------ |        | | |
 |      ------------------------------------------ ||        | | |
 |     | ServerID:        1                       |||        | | |
 |     | Address:         :FFFF:132.151.1.155     |||        | | |
 |     | PublicKeyRecord: HS_DSAKEY, iQCuR2R...   |||        | | |
 |     | ServiceInterface                         |||        | | |
 |     |    ServiceType:          Resolution_Only |||        | | |
 |     |    TransmissionProtocol: TCP & UDP       |||        | | |
 |     |    PortNumber:           2641            |||        | | |
 |     |                                          |||        | | |
 |     |    ServiceType:          Admin only      |||        | | |
 |     |    TransmissionProtocol: TCP             ||         | | |
 |     |    PortNumber:           2642            |          | | |
 |      ------------------------------------------           | | |
 |                                                           | | |
 |  <TTL>:        24 hours                                   | | |
 |  <permission>: PUBLIC_READ, ADMIN_WRITE                   | | |
 |  <reference>:  {empty}                                    | |-
 |                                                           |-
  -----------------------------------------------------------
  Fig. 3.2.2: The primary service site for the naming authority "10"

3.2.3. Naming Authority Delegation Service: HS_NA_DELEGATE

 The HS_NA_DELEGATE is a pre-defined Handle System data type.  It has
 the exact same format as the HS_SITE value.  Like HS_SITE values,
 HS_NA_DELEGATE values are used to describe service sites of a LHS.

Sun, et al. Informational [Page 19] RFC 3651 Handle System Service Definition November 2003

 HS_NA_DELEGATE values may be assigned to naming authority handles to
 designate naming authority administration to a LHS.  A naming
 authority handle with a set of HS_NA_DELEGATE values indicates that
 all child naming authorities of the naming authority are managed by
 the LHS described by the HS_NA_DELEGATE values.
 For example, suppose the naming authority "foo.bar" decides to have
 its child naming authorities delegated to a LHS.  To achieve this,
 one may assign the naming authority handle "0.NA/foo.bar" with a set
 of HS_NA_DELEGATE values that describes the LHS.  The set of
 HS_NA_DELEGATE values indicate that the service information of any
 child naming authority of the "foo.bar", such as "foo.bar.baz", can
 be found by querying the naming authority handle "0.NA/foo.bar.baz"
 from the LHS.

3.2.4. Service Handle: HS_SERV

 Any handle service, global or local, can be defined in terms of a set
 of HS_SITE values.  These HS_SITE values may be assigned directly to
 the relevant naming authority handle, or an additional level of
 indirection may be introduced through the use of service handles.  A
 service handle may be thought of as a name for a handle service.  It
 may be used to maintain the HS_SITE values for the handle service and
 referenced from a naming authority handle via a HS_SERV value.  A
 HS_SERV value is a handle value whose <type> field is HS_SERV and
 whose <data> field contains the reference to the service handle.
 HS_SERV values are typically assigned to naming authority handles to
 refer clients to the responsible handle service.
 Use of service handle allows sharing of service information among
 multiple naming authorities.  It also allows changes to service
 configuration (e.g., adding a new site) to be made in one place
 rather than in every naming authority handle involved.  The mechanism
 may also be used to support service referral from one handle service
 to another for whatever reason.
 A naming authority handle may have no more than one HS_SERV value
 assigned to it, otherwise it is an error.  If a naming authority
 handle has both a list of HS_SITE values and an HS_SERV value, the
 HS_SITE values should be used as the service information for the
 naming authority.
 Service handles can be registered under the reserved naming authority
 "0.SERV".  Handles under "0.SERV" are managed by the GHR. For
 example, the service handle "0.SERV/123" may be created to maintain
 the service information for the handle service that manages handles
 under the naming authority "123" and any of its sub-naming
 authorities.

Sun, et al. Informational [Page 20] RFC 3651 Handle System Service Definition November 2003

 Similarly, a service handle "0.SERV/a.b.c" may be created to host the
 service information for the handle service that manages handles under
 the naming authority "a.b.c".
 The use of service handles raises several special considerations.
 Multiple levels of service handle redirection should be avoided due
 to their lack of efficiency, but are not signaled as an error.
 Looped reference of service handles or HS_SERV values that point to
 non-existent service handles should be caught and error conditions
 passed back to the user.

3.2.5. Alias Handle: HS_ALIAS

 In practice, it is very possible that a digital object may have
 multiple names that will identify the object.  The Handle System
 supports such feature via the pre-defined data type HS_ALIAS.  An
 HS_ALIAS value is a handle value whose <type> field is HS_ALIAS and
 whose <data> field contains a reference to another handle.  A handle
 with a HS_ALIAS value is an alias handle to the handle referenced in
 the HS_ALIAS value.  An alias handle should not have any additional
 handle values other than HS_ALIAS or HS_ADMIN (for administration)
 values.  This is necessary to prevent any inconsistency between a
 handle and its aliases.
 During a handle resolution, a client may get back an HS_ALIAS value.
 This indicates that the handle in question is an alias handle.  The
 client may then retry the query against the handle specified in the
 HS_ALIAS value until final results are obtained.
 The use of alias handle introduces a number of special
 considerations.  For example, multiple levels of aliases should be
 avoided for the sake of efficiency, but are not signaled as an error.
 Alias loops and aliases that point to non-existent handles should be
 caught and error conditions passed back to the user.
 One potential use of alias handle would be to support the transfer of
 ownership of any named resource.  When a resource identified by a
 handle transfers from one organization to another, a new handle for
 the resource may be created.  To avoid inconsistency and any broken
 reference, the handle used before the ownership transfer may be
 changed into an alias handle and point its HS_ALIAS value to the
 newly created handle.

3.2.6. Primary Site: HS_PRIMARY

 HS_PRIMARY is a pre-defined data type used to designate the primary
 service sites for any given handle.  A handle service with multiple
 primary service sites is called a multi-primary service.  Otherwise

Sun, et al. Informational [Page 21] RFC 3651 Handle System Service Definition November 2003

 it is called a single-primary service.  Each handle managed by a
 multi-primary handle service may specify its primary service sites in
 terms of an HS_PRIMARY value.  A HS_PRIMARY value is a handle value
 whose <type> field is HS_PRIMARY and whose <data> field contains a
 list of references to HS_SITE values.  Each of these HS_SITE defines
 a primary service site for the handle.
 There can be at most one HS_PRIMARY value assigned to each handle.
 Otherwise it is an error.  A handle with no HS_PRIMARY value but
 managed by a multi-primary handle service is not an error.  In this
 case, every primary service site of the handle service will also be
 the primary site for the handle.  Handles managed by a single-primary
 handle service do not need any HS_PRIMARY values and any such values
 should be ignored.

3.2.7. Handle Value List: HS_VLIST

 HS_VLIST is a pre-defined data type that allows a handle value to be
 used as a reference to a list of other handle values.  An HS_VLIST
 value is a handle value whose <type> is HS_VLIST and whose <data>
 consists of a 4-byte unsigned integer followed by a list of
 references to other handle values.  The integer specifies the number
 of references in the list.  The references may refer to handle values
 under the same handle or handle values from any other handles.  Each
 reference is encoded as an UTF8-string followed by a 4-byte unsigned
 integer that identifies the referenced handle and its value index.
 HS_VLIST values may be used to define administrator groups for
 handles.  In this case, each reference in the HS_VLIST defines a
 member of the administrator group and the HS_VLIST value identifies
 the group as a whole.  Client software must be careful, however, to
 avoid cyclic definition of value references.

4. Handle System Service Model

 The Handle System is a distributed global name service.  It consists
 of a single distributed Global Handle Registry (GHR) and unlimited
 number of Local Handle Services (LHS).  These service components
 provide the name service (both resolution and administration) on
 behalf of Handle System client components.  Handle System client
 components may also choose to use Handle System middle-ware
 components (e.g., the Handle System caching service) for efficiency.
 This section describes these components and their relationships to
 each other.

Sun, et al. Informational [Page 22] RFC 3651 Handle System Service Definition November 2003

4.1. Handle System Service Components

 The Handle System defines a hierarchical service model.  At the top
 level is the single distributed global handle service, also known as
 the Global Handle Registry (GHR).  Underneath the GHR, there can be
 any number of Local Handle Services (LHSs).  Each LHS must be
 registered with the GHR to manage handles under a distinct set of
 naming authorities.  Naming authorities are managed by the GHR via
 naming authority handles (i.e., handles under the naming authority
 "0.NA").  A naming authority handle can also be used to locate the
 service information (in terms of HS_SITE values) that describes the
 handle service responsible for handles under the naming authority.
 From the service information, clients can choose a service site and
 locate the responsible server for their handle requests.
 Handle System service components are scalable and extensible to
 accommodate any large amount of service load.  A handle service,
 global or local, may consist of multiple service sites, replicating
 each other.  Each service site may also consist of a cluster of
 computers working together to serve its respective namespace. Having
 multiple service sites avoids any single point of failure and allows
 load balancing among these service sites.  Using multiple servers at
 any service site distributes the service load into multiple server
 processes and allows less powerful computers to be utilized for the
 name service.

4.1.1. Global Handle Registry (GHR)

 The Global Handle Registry (GHR) is mainly used to manage naming
 authority handles and to provide service information for every naming
 authority under the Handle System.  The GHR may also be used to
 manage and provide resolution and administration service to non-
 naming-authority handles.  Unlike any LHS, which mostly manages
 handles under a few naming authorities, the GHR is primarily used to
 register naming authorities and provide service information for every
 LHS.  In other words, the GHR is the single root service that
 registers every LHS and provides their service information via the
 use of naming authority handle(s).  Every naming authority under the
 Handle System must be registered under the GHR as a naming authority
 handle.  The naming authority handle provides the service information
 of the handle service that manages all the handles under the naming
 authority.  The service information may be provided in terms of a set
 of HS_SITE values, or an HS_SERV value that refers to a service
 handle, as described earlier.
 The GHR may consist of multiple service sites, each described in a
 HS_SITE value.  These HS_SITE values are assigned to the designated
 naming authority handle "0.NA/0.NA", also called the root handle. The

Sun, et al. Informational [Page 23] RFC 3651 Handle System Service Definition November 2003

 root handle is the naming authority handle that maintains the service
 information for GHR.  Top level naming authorities can only be
 created by administrators of the root handle.
 In order to communicate with the GHR, client software needs the GHR
 service information beforehand.  The service information may be
 distributed initially with the client software, or obtained from some
 other secure sources (e.g., postal mail, secure web site, etc.).
 Client software may keep the service information to communicate with
 the GHR until the service information becomes expired (according to
 its TTL).  The GHR must update its service information (assigned to
 the root handle) every time it changes its configuration.  Client
 software with out-dated service information will be notified of the
 update every time it communicates with the GHR.  The GHR must be
 maintained in such a way that any client software with out-dated GHR
 service information can still query the root handle for the latest
 update.
 Fig. 4.1.1 shows the GHR service information in terms of a set of
 HS_SITE values.  The GHR may consist of a number of service sites,
 each described in a HS_SITE value.  The figure shows a GHR service
 site located in US East Coast, as indicated in the <AttributeList>.

Sun, et al. Informational [Page 24] RFC 3651 Handle System Service Definition November 2003

  1. ———————————————————–
  2. ———————————————————– |
  3. ———————————————————- | |

| | | |

 |  <index>:      3                                          | | |
 |  <type>:       HS_SITE                                    | | |
 |  <data>:                                                  | | |
 |    Version:          1                                    | | |
 |    ProtocolVersion:  2.1                                  | | |
 |    SerialNumber:     1                                    | | |
 |    PrimaryMask:                                           | | |
 |            MultiPrimary:    TRUE                          | | |
 |            PrimarySite:     TRUE                          | | |
 |    HashOption:       HASH_BY_HANDLE                       | | |
 |    HashFilter:       {empty UTF8-String}                  | | |
 |    AttributeList:    1                                    | | |
 |        Description:  Service site at US East Coast        | | |
 |    NumOfServer:      3                                    | | |
 |                                                           | | |
 |        ------------------------------------------         | | |
 |       ------------------------------------------ |        | | |
 |      ------------------------------------------ ||        | | |
 |     | ServerID:        1                       |||        | | |
 |     | Address:         :FFFF:132.151.2.150     |||        | | |
 |     | PublicKeyRecord: HS_DSAKEY, iQCuR2Rnw... |||        | | |
 |     | ServiceInterface                         |||        | | |
 |     |    ServiceType:       Resolution & Admin |||        | | |
 |     |    TransmissionProtocol: TCP & UDP       ||         | | |
 |     |    PortNumber:           2641            |          | | |
 |      ------------------------------------------           | | |
 |                                                           | | |
 |  <TTL>:        24 hours                                   | | |
 |  <permission>: PUBLIC_READ, ADMIN_WRITE                   | | |
 |  <reference>:  {empty}                                    | |-
 |                                                           |-
  -----------------------------------------------------------
        Figure 4.1.1: GHR service information
 The GHR and its service information provide an entry point for any
 client software to communicate with the Handle System.  For any given
 handle, client software can query the GHR for its naming authority
 handle.  This will return the service information of the LHS that
 manages every handle under the naming authority.  The service
 information will direct the client software to the handle server
 within the LHS that manages the handle.

Sun, et al. Informational [Page 25] RFC 3651 Handle System Service Definition November 2003

4.1.2. Local Handle Service (LHS)

 A Local Handle Services (LHS) manages handles under given sets of
 naming authorities.  Each naming authority defines a "local"
 namespace that consists of all of the handles under the naming
 authority.  Note that a LHS is not a "local" service in terms of any
 network topology.  It is called a "Local" Handle Service because it
 typically manages a restricted (local) namespace.
 A naming authority is "homed" at a LHS if all handles under the
 naming authority are managed by the LHS.  A LHS may be home to
 multiple naming authorities.  On the other hand, a naming authority
 may only be "homed" at one LHS.  Note that a naming authority may
 also be homed at the GHR.
  1. ———————————————————–
  2. ———————————————————– |
  3. ———————————————————- | |

| <index>: 3 | | |

 |  <type>:       HS_SITE                                    | | |
 |  <data>:                                                  | | |
 |    Version:          1                                    | | |
 |    ProtocolVersion:  2.1                                  | | |
 |    SerialNumber:     1                                    | | |
 |    PrimaryMask:                                           | | |
 |            MultiPrimary:   FALSE                          | | |
 |            PrimarySite:    TRUE                           | | |
 |    HashOption:       HASH_BY_LOCALNAME                    | | |
 |    HashFilter:       {empty UTF8-String}                  | | |
 |    AttributeList:    1                                    | | |
 |        Description:  Local Service for "10"               | | |
 |    NumOfServer:      2                                    | | |
 |        -----------------------------------------          | | |
 |       ----------------------------------------- |         | | |
 |     | ServerID:        1                       ||         | | |
 |     | Address:         :FFFF:132.151.3.150     ||         | | |
 |     | PublicKeyRecord: HS_DSAKEY, iQCuR2R...   ||         | | |
 |     | ServiceInteface:                         ||         | | |
 |     |    ServiceType:     Resolution & Admin   ||         | | |
 |     |    TransmissionProtocol:     TCP & UDP   ||         | | |
 |     |    PortNumber:               2641        |'         | | |
 |      -----------------------------------------'           | | |
 |  <TTL>:        24 hours                                   | | |
 |  <permission>: PUBLIC_READ, ADMIN_WRITE                   | |-
 |  <reference>:  {empty}                                    |-
  -----------------------------------------------------------
             Figure 4.1.2: LHS service information

Sun, et al. Informational [Page 26] RFC 3651 Handle System Service Definition November 2003

 Like the GHR, a LHS may also consist of many service sites with each
 site described by an HS_SITE value.  The set of HS_SITE values for
 any LHS may be assigned to a service handle or to the relevant naming
 authority handle(s).  Fig. 4.1.2 shows an example of HS_SITE values
 for a LHS.  These HS_SITE values are assigned to the naming authority
 handle "0.NA/10".  This suggests that the naming authority "10" is
 "homed" at the LHS specified in these HS_SITE values. Clients may
 query the GHR to obtain the service information in order to
 communicate with the LHS.  Administrators of the naming authority
 handle are responsible for maintaining the service information and
 keeping it up to date.
 Note that a LHS may refer its clients to another LHS in response to a
 service request.  This allows the LHS to further distribute its
 service in a hierarchical fashion.

4.2. Handle System Middle-Ware Components

 Handle System middle-ware components currently include Handle System
 caching servers and Handle System proxy servers.  These Handle System
 middle-ware components are clients to Handle System service
 components, but servers to Handle System client software. Handle
 System middle-ware components are used to provide additional
 interfaces to the basic handle service.  For example, a Handle System
 caching server may be used to share resolution results within a local
 community.  Additionally, a Handle System proxy server can be used to
 bypass any organizational firewall via HTTP tunneling.

4.2.1. Handle System Caching Service

 Handle System caching service can be used to reduce the network
 traffic between Handle System clients and servers.  Caching handle
 data, including the service information of any LHS, allows re-use of
 information obtained from earlier queries.
 Each handle value contains a <TTL> (Time to Live) field that tells a
 caching service how long the cached value may be regarded as valid.
 A zero-value TTL indicates that the value can only be used for the
 transaction in progress and should not be cached.  A caching service
 may obtain its data directly from a handle service, or from another
 caching service that eventually gets its data from the handle
 service.

Sun, et al. Informational [Page 27] RFC 3651 Handle System Service Definition November 2003

 A caching service may be defined in terms of an HS_SITE value and may
 consist of multiple caching servers.  For any given handle, clients
 can find the responsible caching server within the caching service by
 using the same hashing algorithm as used in locating the handle
 server within any handle service.
 Caching services are not part of any Handle System administration or
 authentication hierarchy.  The Handle System protocol does not
 authenticate any response from a caching service.  Clients are
 responsible to set up their trust relationship with the caching
 service that they select.  They will also rely on the caching service
 to properly authenticate any response from any handle server.

4.2.2. Handle System Proxy Server

 Handle System proxy servers can be used to enable handle resolution
 via other Internet protocols.  For example, CNRI has built and made
 available a Handle System HTTP Proxy Server that will process any
 handle resolution in terms of HTTP protocol.  The current DNS address
 for the proxy server is at "hdl.handle.net".  The proxy server allows
 any handle to be resolved via a HTTP URL.  The URL can be constructed
 as "http://hdl.handle.net/<handle>", where <handle> can be any handle
 from the Handle System.  For example, the handle
 "ncstrl.vatech_cs/tr-93-35" can be resolved via the HTTP URL
 "http://hdl.handle.net/ncstrl.vatech_cs/tr-93-35" from any web
 browser.  In this case, the URL is sent to the proxy server in terms
 of a HTTP request.  The proxy server will query the Handle System for
 the handle data and return the results in terms of HTTP response.
 Using HTTP URLs allows handles to be resolved from standard web
 browsers without any additional client software.  However, such
 reference to the handle also ties itself to the proxy server.  If the
 proxy server changes its DNS name or otherwise becomes invalid, the
 reference (i.e., the HTTP URL) to the handle will break.  Thus the
 selection or use of proxy server should be carefully evaluated.
 Proxy servers are not part of any Handle System administration or
 authentication hierarchy.  The Handle System protocol does not
 authenticate any response from a proxy server.  Clients are
 responsible to set up their trust relationship with the proxy server
 that they select.  They will also rely on the proxy server to
 properly authenticate any response from any handle server.

4.3. Handle System Client Components

 Handle System client components are client software that communicates
 with the Handle System service components.  Client software may speak
 the Handle System protocol and send its request directly to a service

Sun, et al. Informational [Page 28] RFC 3651 Handle System Service Definition November 2003

 component.  The response from the service component may be the final
 answer to the request, or a referral to another service component.
 The client software will have to follow the referral in order to
 complete the transaction.
 Client software may also be configured to tunnel its request via a
 middle-ware component.  The middle-ware component will thus be
 responsible for obtaining the final result and returning it to the
 client.  Unlike service components, middle-ware components will only
 return final results of client's request.  No service referral will
 be returned from middle-ware components.
 Various Handle System client components may be developed for various
 applications.  The CNRI Handle System Resolver [17] is one such
 component.  The resolver extends web browsers (e.g., Netscape or
 Microsoft Internet Explorer) in such a way that handles can be
 resolved directly in terms of "hdl:" Uniform Resource Identifiers
 (URIs).  The Grail web browser [18], a freely downloadable software
 developed in Python [19], also supports the "hdl:" URI scheme and
 will resolve handles accordingly.  For example, the handle
 "10.1045/july95-arms" may be resolved by entering its handle URI as
 "hdl:10.1045/july95-arms" into any of these resolver-enabled
 browsers.  Details of the handle URI syntax will be specified in a
 separate document.

5. Handle System Operation Model

 Handle System operations can be categorized into resolution and
 administration.  Clients use the handle resolution service to query
 for any handle values.  Handle administration allows clients to
 manage handles, including adding and deleting handles, and updating
 their values.  It also deals with naming authority administration via
 naming authority handles.  This section explains how various Handle
 System components work together to accomplish these service
 operations.
 Both resolution and administration may require authentication of the
 client.  The authentication can be done via the Handle System
 authentication protocol described later in this section.  Whether
 authentication is required or not depends on the kind of operation
 involved and the permissions assigned to the relevant handle value,
 and policies deployed by the relevant service components.
 The Handle System protocol specifies the syntax and semantics of each
 message exchanged between Handle System clients and its server
 components.  This section provides a high level overview of the

Sun, et al. Informational [Page 29] RFC 3651 Handle System Service Definition November 2003

 protocol used to accomplish any service operation.  The exact
 programmatic detail of each message (i.e., their byte layout or
 syntax) is specified in a separate document [8].

5.1. Handle System Service Request and Response

 The Handle System provides its service in response to client
 requests.  A client may send a request to any handle server to
 provoke a response.  The response either provides an answer to the
 request, or a status code with associated information that either
 refers the request to another service component, asks for client
 authentication, or signals some error status.
 Each handle under the Handle System is managed by its home service.
 The naming authority handle provides the service information (in
 terms of HS_SERV or HS_SITE values) of the handle service that
 manages all handles under the naming authority.  Any handle request
 must be directed to the home service of the handle in question.
 Clients may find the home service by querying the corresponding
 naming authority handle against the GHR.  Alternatively, this
 information may be found in a local cache or even be part of a local
 client configuration.  Given the service information, clients may
 select a service site and locate the responsible handle server within
 the site.
 To resolve the handle "ncstrl.vatech_cs/te-93-35", for example,
 client software needs to know the home service for the naming
 authority "ncstrl.vatech_cs".  The home service can be obtained by
 querying the naming authority handle "0.NA/ncstrl.vatech_cs" against
 the GHR.  The GHR will return the service information in terms of the
 HS_SITE values assigned to the naming authority handle.  From the
 service information, clients can pick a service site, find the
 responsible handle server within the site, and send the resolution
 request to the handle server.
 Clients may require digital signatures from a handle server in order
 to authenticate any response from the server.  The signature can be
 generated using the server's private key.  Clients may verify the
 signature using the public key available from the service information
 (refer to the <PublicKeyRecord> entry discussed in 3.2.2).
 A communication session may also be established between any client
 and handle server.  Each session is identified by a unique session ID
 managed by the server.  A session may be used to manage requests that
 require multiple interactions.  It may also be used to share any TCP
 connection or authentication information among multiple service
 transactions.  Each session may establish a session key and use it to

Sun, et al. Informational [Page 30] RFC 3651 Handle System Service Definition November 2003

 authenticate any message exchanged within the session.  It may also
 be used to encrypt any message between the client and the server to
 achieve data confidentiality.
 The following diagram shows a handle resolution process in terms of
 messages exchanged between client software and Handle System service
 components.  In this case, the client is trying to resolve the handle
 "ncstrl.vatech_cs/tr-93-35".  It assumes that the client has yet
 obtained the service information of the LHS "homed" by the naming
 authority "ncstrl.vatech.cs".  The client has to get the service
 information from the naming authority handle managed by the GHR.  The
 service information allows the client to locate the responsible LHS
 and query for the handle value.
 [HS Client]  ----------------------------> [Global Handle Registry]
               1. ask for the service
                  information from the
                  naming authority handle
                  "0.NA/ncstrl.vatech_cs"
 [HS Client]  <---------------------------- [Global Handle Registry]
               2. service information for
                  the naming authority
                  "ncstrl.vatech_cs"
 [HS Client]  ----------------------------> [Local Handle Service]
               3. query the handle
                  "ncstrl.vatech_cs/tr-93-35"
                  against the responsible
                  handle server
   \... ...
  (optional client authentication, depending on the service request)
   \... ...
 [HS Client]  <---------------------------- [Local Handle Service]
                4. query result from the handle
                   server + (optional) server
                   signature
             Figure 5.1: Handle resolution example
 In Figure 5.1, the client is configured to communicate with the GHR
 for any handle service.  In this case, the client first queries the
 GHR to find the home service for the handle's naming authority.  The

Sun, et al. Informational [Page 31] RFC 3651 Handle System Service Definition November 2003

 GHR returns the service information of the LHS that manages every
 handle under the naming authority.  From the service information, the
 client can find the responsible handle server and query the server
 for the handle.  The server may set up a session to authenticate the
 client if any of the handle value requires authentication.
 Otherwise, the server will simply return the handle value to the
 client.  The server may send a digital signature as part of its
 response if required by the client.
 The above procedure assumes that the client software already has the
 GHR service information.  That information was likely obtained from
 the client software distribution.  The GHR will notify the client
 software if it learns that the service information used by the client
 software is out of date.  Client software may retrieve the latest
 service information from the root handle "0.NA/0.NA". The root handle
 also maintains the public key that may be used to authenticate the
 service information.
 Note that a client may cache the service information of any naming
 authority so that subsequent queries for handles under the same
 naming authority may reuse the service information and bypass the
 first two steps shown in Figure 5.1.  Client software may also be
 configured to query a caching or proxy server directly for any
 handle.  In this case, the caching or proxy server will act as the
 [HS Client] in Figure 5.1 before returning the query result to the
 client.
 Client software under certain organization may also elect to bypass
 the GHR and communicate directly with a LHS managed by the
 organization.  Doing so may achieve quicker response for handles
 managed under the LHS.  The client software will be referred to the
 GHR for handles not managed by the LHS.

5.2. Handle System Authentication Protocol

 The Handle System supports handle administration over the public
 Internet.  Access controls can be defined on each handle value.  The
 Handle System authentication protocol is the protocol used by any
 handle server to authenticate handle administrator upon any
 administration request.  The authentication is also necessary when
 clients query for handle values that are read-only by the handle
 administrator.  Handle administration include adding, deleting or
 modifying handle values, and adding or deleting handles.  Naming
 authority administrations are carried out as handle administrations
 over the corresponding naming authority handles.

Sun, et al. Informational [Page 32] RFC 3651 Handle System Service Definition November 2003

 The Handle System authentication protocol does not perform any server
 authentication.  However, a client may authenticate any server
 response by asking the server to sign its response with digital
 signature.
 By default, the Handle System authenticates clients via a challenge-
 response protocol.  That is, after receiving a client's request, the
 server issues a challenge to the client if authentication is
 necessary.  To be authenticated as the administrator, the client has
 to return a challenge-response, a message that demonstrates
 procession of the administrator's secret. The secret may be the
 private key or the secret key of the administrator.  This challenge-
 response allows the server to authenticate the client as the handle
 administrator.  Upon successful authentication, the server will
 fulfill the client's request if the administrator is given sufficient
 permission.
 For example, suppose a client sends a request to the handle server to
 add a new handle value.  The server will issue a challenge to the
 client in order to authenticate the client as one of the handle
 administrators.  If the client possesses the private key of the
 administrator, she can use it to sign the server's challenge and
 return the signature as part of her challenge-response.  The server
 will validate the signature in order to authenticate the client. The
 client will be notified if the validation fails.  Otherwise, the
 server will further check if the administrator has the permission to
 add the handle value.  If so, the server will add the handle value
 and report success to the client.  Otherwise, a permission-denied
 message will be returned.

Sun, et al. Informational [Page 33] RFC 3651 Handle System Service Definition November 2003

 The following diagram shows a typical authentication process in terms
 of the messages exchanged between the client and the handle server.
   [Client]  -------------------------------->  [Handle Server]
               1. client request
                + (optional) client credential
   [Client]  <--------------------------------  [Handle Server]
               2. server's challenge to client
                + (i.e., nonce + MD5 of client request)
   [Client]  ------------------------------->   [Handle Server]
               3. reference to handle administrator
                + challenge-response from client
   [Client]  <-------------------------------   [Handle Server]
               4. server acknowledgement
         Figure 5.2: Handle System authentication process
 In Figure 5.2, the client sends an administration request to the
 handle server (along with optional credential discussed later).  The
 server decides that client authentication is required and issues a
 challenge to the client.  The client identifies itself as a handle
 administrator and returns the challenge-response to the server.  The
 server authenticates the client as the administrator based on the
 challenge-response.  It also checks to see if the administrator is
 authorized for the administration request.  If so, the server will
 fulfill the request and acknowledge the client.
 Handle servers must authenticate the client before fulfilling any
 request that requires administrator privilege.  The exact
 authentication process varies depending on whether public key or
 secret key is used by the administrator.  It also depends on whether
 the handle used to store the administrator's key is managed by the
 same handle server or not.
 When public key is used, the challenge-response from the client
 contains its digital signature over the server's challenge.  The
 server can authenticate the client by verifying the digital signature
 based on the administrator's public key.  If secret key is used, the
 challenge-response from the client carries the Message Authenticate
 Code (MAC) generated using the secret key.  The server may
 authenticate the client by generating the same MAC using the
 administrator's secret key and comparing it against the challenge-
 response.

Sun, et al. Informational [Page 34] RFC 3651 Handle System Service Definition November 2003

 The reference to handle administrator in Fig 5.2 is also called a
 key-reference.  It refers to a handle value that contains the key
 used by the administrator.  If the key-reference is managed by the
 same handle server (e.g., a handle value assigned to the same
 handle), the server may use the key directly to do the
 authentication.  If the key-reference is managed by some other handle
 server (whether or not within the same handle service), the server
 will have to send a verification-request to this other handle server,
 call it the key-server, in order to authenticate the client.  The
 verification-request to the key-server carries both the server's
 challenge and the client's challenge-response.  The key-server will
 return a verification-response, signed using the key-server's private
 key.  The content of the verification-response will depend on the
 handle value referenced by the key-reference.  If the key-reference
 refers to a public key used by the administrator, the verification-
 response will contain the public key of the administrator.
 Otherwise, the key-server will verify the challenge-response on
 behalf of the requesting server and return the result in the
 verification-response.  The following diagram shows the control flow
 of the authentication process where the key-reference refers to a
 handle value that contains the administrator's public (or secret) key
 and the key-server is some other handle server.

Sun, et al. Informational [Page 35] RFC 3651 Handle System Service Definition November 2003

  1. ——- ————-

| | 1. client request. | |

   |        | ------------------------------->  |             |
   |        |                                   |             |
   |        |   2.  session ID                  |             |
   |        |     + server's challenge          |             |
   | Handle | <-------------------------------  | Handle      |
   | System |                                   | server      |
   | client |   3.  session ID                  | receiving   |
   |        |     + response to the challenge   | client      |
   |        |     + administrator reference     | request     |
   |        | --------------------------------> |             |
   |        |                                   |             |
   |        |   6.  server acknowledgement      |             |
   |        | <-------------------------------  |             |
    --------                                     -------------
                                                     |  ^
                                     4. Verification |  | 5. verifi-
                                        request      |  |    cation
                                                     |  |    response
                                                     |  |    (signed)
                                                     V  |
                                          --------------------------
                                         | The handle server (the   |
                                         | key-server) that manages |
                                         | the key referenced by    |
                                         | the key-reference        |
                                          --------------------------
        Figure 5.3: Authentication process requiring verification
                    from a second handle server
 Secret key based authentication via a second handle server, i.e., the
 key server, provides a convenient way to share a common secret key
 (e.g., pass phrase) among handles managed by different handle
 servers.  However, it should not be used to manage highly sensitive
 handles or handle data.  The authentication process itself is
 expensive and relies on a third party, i.e., the key-server, for
 proper operation.  Additionally, the secret key itself is subject to
 dictionary attack since the key-server cannot determine whether the
 verification-request comes from a legitimate handle server.  A handle
 service may set its local policy so that secret key based
 authentication can only be carried out if the handle server
 (receiving the client request) is also the key-server.

Sun, et al. Informational [Page 36] RFC 3651 Handle System Service Definition November 2003

 Local handle services may define additional local policies for
 authentication and/or authorization.  Handle System service
 components may also choose to use other Internet authentication
 mechanisms such as Kerberos [20] or some Transport Layer Security
 protocol [21].  Details of these will be addressed in a separate
 document.

6. Security Considerations

 Handle System security considerations are discussed in the "Handle
 System Overview" [1] and that discussion applies equally to this
 document.
 The Handle System delegates handle administration to each handle
 administrator who may or may not be the server administrator.  Handle
 administrators are allowed to choose their own public/secret keys
 used for authentication.  The security of Handle System
 authentication depends on the proper key selection and its
 maintenance by the handle administrator.  Handle administrators must
 choose and protect their authentication keys carefully in order to
 protect the handle data.  Handle server implementations may deploy
 policies that regulate the selection of public/secret keys used for
 authentication.  For example, a handle server may require that any
 authentication key must be no less than certain number of bits.  It
 may also prohibit the use of secret keys because of the potential
 dictionary attack.
 The Handle System data model supports execution permission
 (PUBLIC_EXECUTE, ADMIN_EXECUTE) for each handle value.  While this
 allows better sharing of network resources, it also raises many
 security considerations.  Execution privilege should be restricted
 within the permissions of certain user account (corresponding to the
 handle administrator) on the server to prevent system-wide
 disruption.  Switching between computing platforms for the server
 should also be careful to avoid any unexpected behavior.
 Implementations may choose not to support the execution permission,
 or provide options so that it can be disabled.
 To protect against any irresponsible use of system resource, handle
 servers may implement quota control.  The quota control can be used
 to put limits on the number of handles under a naming authority, the
 number of handle values allowed for any given handle, the maximum
 size of any handle value, and the number of sub-naming authorities
 under a naming authority.  Handle servers must report error if the
 result of a handle administration violates any of these limits.

Sun, et al. Informational [Page 37] RFC 3651 Handle System Service Definition November 2003

7. Acknowledgements

 This work is derived from the earlier versions of the Handle System
 implementation. The overall digital object architecture, including
 the Handle System, was described in a paper by Robert Kahn and Robert
 Wilensky [22] in 1995. Development continued at CNRI as part of the
 Computer Science Technical Reports (CSTR) project, funded by the
 Defense Advanced Projects Agency (DARPA) under Grant Number MDA-972-
 92-J-1029 and MDA-972-99-1-0018.  Design ideas are based on those
 discussed within the Handle System development team, including David
 Ely, Charles Orth, Allison Yu, Sean Reilly, Jane Euler, Catherine
 Rey, Stephanie Nguyen, Jason Petrone, and Helen She.  Their
 contributions to this work are gratefully acknowledged.
 The authors also thank Russ Housley (housley@vigilsec.com), Ted
 Hardie (hardie@qualcomm.com), and Mark Baugher (mbaugher@cisco.com)
 for their extensive review and comments, as well as recommendations
 received from other members of the IETF/IRTF community.

8. References and Bibliography

 [1]  Sun, S. and L. Lannom, "Handle System Overview", RFC 3650,
      November 2003.
 [2]  Mockapetris, P., "Domain Names - Concepts and Facilities," STD
      13, RFC 1034, November 1987.
 [3]  Mockapetris, P., "Domain Names - Implementation and
      Specification", STD 13, RFC 1035, November 1987.
 [4]  Wahl, M., Howes, T. and S. Kille, "Lightweight Directory Access
      Protocol (v3)", RFC 2251, December 1997.
 [5]  Crocker, D., Ed. and  P. Overell, "Augmented BNF for Syntax
      Specifications: ABNF", RFC 2234, November 1997.
 [6]  Yergeau, F., "UTF-8, A Transform Format for Unicode and
      ISO10646", RFC 2279, January 1998.
 [7]  The Unicode Consortium, "The Unicode Standard, Version 2.0",
      Addison-Wesley Developers Press, 1996.  ISBN 0-201-48345-9
 [8]  Sun, S., Reilly, S. and L. Lannom, "Handle System Protocol (ver
      2.1) Specification", RFC 3652, November 2003.
 [9]  Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform Resource
      Locators (URL)", RFC 1738, December 1994.

Sun, et al. Informational [Page 38] RFC 3651 Handle System Service Definition November 2003

 [10] Housley, R., Polk, W. Ford, W. and D. Solo, "Internet X.509
      Public Key Infrastructure - Certificate and Certificate
      Revocation List (CRL) Profile", RFC 3280, April 2002.
 [11] Federal Information Processing Standards Publication (FIPS PUB)
      46-1, Data Encryption Standard, Reaffirmed 1988 January 22
      (supersedes FIPS PUB 46, 1977 January 15).
 [12] Federal Information Processing Standards Publication (FIPS PUB)
      81, DES Modes of Operation, 1980 December 2.
 [13] Balenson, D., "Privacy Enhancement for Internet Electronic Mail:
      Part III: Algorithms, Modes, and Identifiers", RFC 1423,
      February 1993.
 [14] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April
      1992.
 [15] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
      Specification", RFC 1883, December 1995.
 [16] Hinden, R. and S. Deering, "IP Version 6 Addressing
      Architecture", RFC 2373, July 1998.
 [17] CNRI Handle System Resolver, http://www.handle.net/resolver
 [18] Grail browser home page, http://grail.sourceforge.net/
 [19] Python language website, http://www.python.org/
 [20] Kohl, J. and C. Neuman, "The Kerberos Network Authentication
      Service (V5)", RFC 1510, September 1993.
 [21] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC
      2246, January 1999.
 [22] R. Kahn, R. Wilensky, "A Framework for Distributed Digital
      Object Services, May 1995, http://www.cnri.reston.va.us/k-w.html
 [23] American National Standards Institute.  ANSI X9.52-1998, Triple
      Data Encryption Algorithm Modes of Operation. 1998.

Sun, et al. Informational [Page 39] RFC 3651 Handle System Service Definition November 2003

9. Authors' Addresses

 Sam X. Sun
 Corporation for National Research Initiatives (CNRI)
 1895 Preston White Dr., Suite 100
 Reston, VA 20191
 Phone: 703-262-5316
 EMail: ssun@cnri.reston.va.us
 Sean Reilly
 Corporation for National Research Initiatives (CNRI)
 1895 Preston White Dr., Suite 100
 Reston, VA 20191
 Phone: 703-620-8990
 EMail: sreilly@cnri.reston.va.us
 Larry Lannom
 Corporation for National Research Initiatives (CNRI)
 1895 Preston White Dr., Suite 100
 Reston, VA 20191
 Phone: 703-620-8990
 EMail: llannom@cnri.reston.va.us

Sun, et al. Informational [Page 40] RFC 3651 Handle System Service Definition November 2003

10. Full Copyright Statement

 Copyright (C) The Internet Society (2003).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assignees.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Sun, et al. Informational [Page 41]

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