GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc7844

Internet Engineering Task Force (IETF) C. Huitema Request for Comments: 7844 Microsoft Category: Standards Track T. Mrugalski ISSN: 2070-1721 ISC

                                                           S. Krishnan
                                                              Ericsson
                                                              May 2016
                Anonymity Profiles for DHCP Clients

Abstract

 Some DHCP options carry unique identifiers.  These identifiers can
 enable device tracking even if the device administrator takes care of
 randomizing other potential identifications like link-layer addresses
 or IPv6 addresses.  The anonymity profiles are designed for clients
 that wish to remain anonymous to the visited network.  The profiles
 provide guidelines on the composition of DHCP or DHCPv6 messages,
 designed to minimize disclosure of identifying information.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7844.

Huitema, et al. Standards Track [Page 1] RFC 7844 DHCP Anonymity Profiles May 2016

Copyright Notice

 Copyright (c) 2016 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Huitema, et al. Standards Track [Page 2] RFC 7844 DHCP Anonymity Profiles May 2016

Table of Contents

 1. Introduction ....................................................4
    1.1. Requirements ...............................................4
 2. Application Domain ..............................................4
    2.1. MAC Address Randomization Hypotheses .......................5
    2.2. MAC Address Randomization and DHCP .........................6
    2.3. Radio Fingerprinting .......................................6
    2.4. Operating System Fingerprinting ............................7
    2.5. No Anonymity Profile Identification ........................7
    2.6. Using the Anonymity Profiles ...............................8
    2.7. What about privacy for DHCP servers? .......................9
 3. Anonymity Profile for DHCPv4 ....................................9
    3.1. Avoiding Fingerprinting ...................................10
    3.2. Client IP Address Field ...................................10
    3.3. Requested IP Address Option ...............................11
    3.4. Client Hardware Address Field .............................12
    3.5. Client Identifier Option ..................................12
    3.6. Parameter Request List Option .............................13
    3.7. Host Name Option ..........................................13
    3.8. Client FQDN Option ........................................14
    3.9. UUID/GUID-Based Client Machine Identifier Option ..........15
    3.10. User and Vendor Class DHCP Options .......................15
 4. Anonymity Profile for DHCPv6 ...................................15
    4.1. Avoiding Fingerprinting ...................................16
    4.2. Do not send Confirm messages, unless really sure about
         the location ..............................................17
    4.3. Client Identifier DHCPv6 Option ...........................17
         4.3.1. Anonymous Information-request ......................18
    4.4. Server Identifier Option ..................................18
    4.5. Address Assignment Options ................................18
         4.5.1. Obtain Temporary Addresses .........................19
         4.5.2. Prefix Delegation ..................................20
    4.6. Option Request Option .....................................20
         4.6.1. Previous Option Values .............................20
    4.7. Authentication Option .....................................21
    4.8. User and Vendor Class DHCPv6 Options ......................21
    4.9. Client FQDN DHCPv6 Option .................................21
 5. Operational Considerations .....................................21
 6. Security Considerations ........................................22
 7. References .....................................................22
    7.1. Normative References ......................................22
    7.2. Informative References ....................................23
 Acknowledgments ...................................................26
 Authors' Addresses ................................................26

Huitema, et al. Standards Track [Page 3] RFC 7844 DHCP Anonymity Profiles May 2016

1. Introduction

 There have been reports of systems that would monitor the wireless
 connections of passengers at Canadian airports [CNBC].  We can assume
 that these are either fragments or trial runs of a wider system that
 would attempt to monitor Internet users as they roam through wireless
 access points and other temporary network attachments.  We can also
 assume that privacy-conscious users will attempt to evade this
 monitoring -- for example, by ensuring that low-level identifiers
 such as link-layer addresses are "randomized", so that the devices
 do not broadcast the same unique identifier in every location that
 they visit.
 Of course, link-layer MAC (Media Access Control) addresses are not
 the only way to identify a device.  As soon as it connects to a
 remote network, the device may use DHCP and DHCPv6 to obtain network
 parameters.  The analysis of DHCP and DHCPv6 options shows that
 parameters of these protocols can reveal identifiers of the device,
 negating the benefits of link-layer address randomization.  This is
 documented in detail in [RFC7819] and [RFC7824].  The natural
 reaction is to restrict the number and values of such parameters in
 order to minimize disclosure.
 In the absence of a common standard, different system developers are
 likely to implement this minimization of disclosure in different
 ways.  Monitoring entities could then use the differences to identify
 the software version running on the device.  The proposed anonymity
 profiles provide a common standard that minimizes information
 disclosure, including the disclosure of implementation identifiers.

1.1. Requirements

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].

2. Application Domain

 Mobile nodes can be tracked using multiple identifiers, the most
 prominent being link-layer addresses, a.k.a. MAC addresses.  For
 example, when devices use Wi-Fi connectivity, they place the MAC
 address in the header of all the packets that they transmit.
 Standard implementations of Wi-Fi use unique 48-bit link-layer
 addresses, assigned to the devices according to procedures defined by
 IEEE 802.  Even when the Wi-Fi packets are encrypted, the portion of
 the header containing the addresses will be sent in cleartext.
 Tracking devices can "listen to the airwaves" to find out what
 devices are transmitting near them.

Huitema, et al. Standards Track [Page 4] RFC 7844 DHCP Anonymity Profiles May 2016

 We can easily imagine that the MAC addresses can be correlated with
 other data, e.g., cleartext names and cookies, to build a registry
 linking MAC addresses to the identity of devices' owners.  Once that
 correlation is done, tracking the MAC address is sufficient to track
 individual people, even when all application data sent from the
 devices is encrypted.  Link-layer addresses can also be correlated
 with IP addresses of devices, negating the potential privacy benefits
 of IPv6 "privacy" addresses.  Privacy advocates have reasons to be
 concerned.
 The obvious solution is to "randomize" the MAC address.  Before
 connecting to a particular network, the device replaces the MAC
 address with a randomly drawn 48-bit value.  Link-layer address
 randomization was successfully tried at the IETF meeting in Honolulu
 in November 2014 [IETFMACRandom] and in subsequent meetings
 [IETFTrialsAndMore]; it is studied in the IEEE 802 EC Privacy
 Recommendation Study Group [IEEE802PRSG].  However, we have to
 consider the linkage between link-layer addresses, DHCP identifiers,
 and IP addresses.

2.1. MAC Address Randomization Hypotheses

 There is not yet an established standard for randomizing link-layer
 addresses.  Various prototypes have tried different strategies,
 such as:
 Per connection:  Configure a random link-layer address at the time of
    connecting to a network, e.g., to a specific Wi-Fi SSID (Service
    Set Identifier), and keep it for the duration of the connection.
 Per network:  Same as "per connection", but always use the same
    link-layer address for the same network -- different, of course,
    from the addresses used in other networks.
 Time interval:  Change the link-layer address at regular time
    intervals.
 In practice, there are many reasons to keep the link-layer address
 constant for the duration of a link-layer connection, as in the
 "per connection" or "per network" variants.  In Wi-Fi networks,
 changing the link-layer address requires dropping the existing Wi-Fi
 connection and then re-establishing it, which implies repeating the
 connection process and associated procedures.  The IP addresses will
 change, which means that all required TCP connections will have to be
 re-established.  If the network access is provided through a NAT,
 changing IP addresses also means that the NAT traversal procedures
 will have to be restarted.  This means a lot of disruption.  At the
 same time, an observer on the network will easily notice that a

Huitema, et al. Standards Track [Page 5] RFC 7844 DHCP Anonymity Profiles May 2016

 station left, another came in just after that, and the new one
 appears to be communicating with the same set of IP addresses as the
 old one.  This provides for easy correlation.
 The anonymity profiles pretty much assume that the link-layer address
 randomization follows the "per connection" or "per network"
 strategies, or a variant of the "time interval" strategy in which the
 interval has about the same duration as the average connection.

2.2. MAC Address Randomization and DHCP

 From a privacy point of view, it is clear that the link-layer
 address, IP address, and DHCP identifier shall evolve in synchrony.
 For example, if the link-layer address changes and the DHCP
 identifier stays constant, then it is really easy to correlate old
 and new link-layer addresses, either by listening to DHCP traffic or
 by observing that the IP address remains constant, since it is tied
 to the DHCP identifier.  Conversely, if the DHCP identifier changes
 but the link-layer address remains constant, the old and new
 identifiers and addresses can be correlated by listening to L2
 traffic.  The procedures documented in the following sections
 construct DHCP identifiers from the current link-layer address,
 automatically providing for this synchronization.
 The proposed anonymity profiles solve this synchronization issue by
 deriving most identifiers from the link-layer address and by
 generally making sure that DHCP parameter values do not remain
 constant after an address change.

2.3. Radio Fingerprinting

 MAC address randomization solves the trivial monitoring problem in
 which someone just uses a Wi-Fi scanner and records the MAC addresses
 seen on the air.  DHCP anonymity solves the more elaborate scenario
 in which someone monitors link-layer addresses and identities used in
 DHCP at the access point or DHCP server.  But these are not the only
 ways to track a mobile device.
 Radio fingerprinting is a process that identifies a radio transmitter
 by the unique "fingerprint" of its signal transmission, i.e., the
 tiny differences caused by minute imperfections of the radio
 transmission hardware.  This can be applied to diverse types of
 radios, including Wi-Fi as described, for example, in
 [WiFiRadioFingerprinting].  No amount of link-layer address
 randomization will protect against such techniques.  Protections may
 exist, but they are outside the scope of the present document.

Huitema, et al. Standards Track [Page 6] RFC 7844 DHCP Anonymity Profiles May 2016

 On the other hand, we should not renounce randomization just because
 radio fingerprinting exists.  The radio fingerprinting techniques are
 harder to deploy than just recording link-layer addresses with a
 scanner.  Such techniques can only track devices for which the
 fingerprints are known and thus have a narrower scope of application
 than mass monitoring of addresses and DHCP parameters.

2.4. Operating System Fingerprinting

 When a standard like DHCP allows for multiple options, different
 implementers will make different choices for the options that they
 support or the values they choose for the options.  Conversely,
 monitoring the options and values present in DHCP messages reveals
 these differences and allows for "operating system fingerprinting",
 i.e., finding the type and version of software that a particular
 device is running.  Finding these versions provides some information
 about the device's identity and thus goes against the goal of
 anonymity.
 The design of the anonymity profiles attempts to minimize the number
 of options and the choice of values, in order to reduce the
 possibilities of operating system fingerprinting.

2.5. No Anonymity Profile Identification

 Reviewers of the anonymity profiles have sometimes suggested adding
 an option to explicitly identify the profiles as "using the anonymity
 option".  One suggestion is that the client tell the server about its
 desire to remain anonymous, so that a willing server could cooperate
 and protect the client's privacy.  Another possibility would be to
 use a specific privacy-oriented construct, such as, for example, a
 new type of DHCP Unique Identifier (DUID) for a temporary DUID that
 would be changing over time.
 This is not workable in a large number of cases, as it is possible
 that the network operator (or other entities that have access to the
 operator's network) might be actively participating in surveillance
 and anti-privacy, willingly or not.  Declaring a preference for
 anonymity is a bit like walking around with a Guy Fawkes mask.  (See
 [GuyFawkesMask] for an explanation of this usage.)  When anonymity is
 required, it is generally not a good idea to stick out of the crowd.
 Simply revealing the desire for privacy could cause the attacker to
 react by triggering additional surveillance or monitoring mechanisms.
 Therefore, we feel that it is preferable to not disclose one's desire
 for privacy.

Huitema, et al. Standards Track [Page 7] RFC 7844 DHCP Anonymity Profiles May 2016

 This preference leads to some important implications.  In particular,
 we make an effort to make the mitigation techniques difficult to
 distinguish from regular client behaviors, if at all possible.

2.6. Using the Anonymity Profiles

 There are downsides to randomizing link-layer addresses and DHCP
 identifiers.  By definition, randomization will break management
 procedures that rely on tracking link-layer addresses.  Even if this
 is not too much of a concern, we have to be worried about the
 frequency of link-layer address randomization.  Suppose, for example,
 that many devices would get new random link-layer addresses at short
 intervals, maybe every few minutes.  This would generate new DHCP
 requests in rapid succession, with a high risk of exhausting DHCPv4
 address pools.  Even with IPv6, there would still be a risk of
 increased neighbor discovery traffic and bloating of various address
 tables.  Implementers will have to be cautious when programming
 devices to use randomized MAC addresses.  They will have to carefully
 choose the frequency with which such addresses will be renewed.
 This document only provides guidelines for using DHCP when clients
 care about privacy.  We assume that the request for anonymity is
 materialized by the assignment of a randomized link-layer address to
 the network interface.  Once that decision is made, the following
 guidelines will avoid leakage of identity in DHCP parameters or in
 assigned addresses.
 There may be rare situations where the clients want to remain
 anonymous to attackers but not to the DHCP server.  These clients
 should still use link-layer address randomization to hide from
 observers, as well as some form of encrypted communication to the
 DHCP server.  This scenario is out of scope for this document.
 To preserve anonymity, the clients need to not use stable values for
 the client identifiers.  This is clearly a trade-off, because a
 stable client identifier guarantees that the client will receive
 consistent parameters over time.  An example is given in [RFC7618],
 where the client identifier is used to guarantee that the same client
 will always get the same combination of IP address and port range.
 Static clients benefit most from stable parameters and often can
 already be identified by physical-connection-layer parameters.  These
 static clients will normally not use the anonymity profiles.  Mobile
 clients, in contrast, have the option of using the anonymity profiles
 in conjunction with [RFC7618] if they are more concerned with privacy
 protection than with stable parameters.

Huitema, et al. Standards Track [Page 8] RFC 7844 DHCP Anonymity Profiles May 2016

2.7. What about privacy for DHCP servers?

 This document only provides recommendations for DHCP clients.  The
 main targets are DHCP clients used in mobile devices.  Such devices
 are tempting targets for various monitoring systems, so there is an
 urgent need to provide them with a simple anonymity solution.  We can
 argue that some mobile devices embed DHCP servers and that providing
 solutions for such devices is also quite important.  Two plausible
 examples would be a DHCP server for a car network and a DHCP server
 for a mobile hot spot.  However, mobile servers get a lot of privacy
 protection through the use of access control and link-layer
 encryption.  Servers may disclose information to clients through
 DHCP, but they normally only do that to clients that have passed the
 link-layer access control and have been authorized to use the network
 services.  This arguably makes solving the server problem less urgent
 than solving the client problem.
 Server privacy issues are presented in [RFC7819] and [RFC7824].
 Mitigation of these issues is left for further study.

3. Anonymity Profile for DHCPv4

 Clients using the DHCPv4 anonymity profile limit the disclosure of
 information by controlling the header parameters and by limiting the
 number and values of options.  The number of options depends on the
 specific DHCP message:
 DHCPDISCOVER:  The anonymized DHCPDISCOVER messages MUST contain the
    Message Type option, MAY contain the Client Identifier option, and
    MAY contain the Parameter Request List option.  It SHOULD NOT
    contain any other option.
 DHCPREQUEST:  The anonymized DHCPREQUEST messages MUST contain the
    Message Type option, MAY contain the Client Identifier option, and
    MAY contain the Parameter Request List option.  If the message is
    in response to a DHCPOFFER, it MUST contain the corresponding
    Server Identifier option and the Requested IP address option.  If
    the message is not in response to a DHCPOFFER, it MAY contain a
    Requested IP address option as explained in Section 3.3.  It
    SHOULD NOT contain any other option.
 DHCPDECLINE:  The anonymized DHCPDECLINE messages MUST contain the
    Message Type option, the Server Identifier option, and the
    Requested IP address option; and MAY contain the Client Identifier
    option.

Huitema, et al. Standards Track [Page 9] RFC 7844 DHCP Anonymity Profiles May 2016

 DHCPRELEASE:  The anonymized DHCPRELEASE messages MUST contain the
    Message Type option and the Server Identifier option, and MAY
    contain the Client Identifier option.
 DHCPINFORM:  The anonymized DHCPINFORM messages MUST contain the
    Message Type option, MAY contain the Client Identifier option, and
    MAY contain the Parameter Request List option.  It SHOULD NOT
    contain any other option.
 Header fields and option values SHOULD be set in accordance with the
 DHCP specification, but some header fields and option values SHOULD
 be constructed per the following guidelines.
 The inclusion of the Host Name and Fully Qualified Domain Name (FQDN)
 options in DHCPDISCOVER, DHCPREQUEST, or DHCPINFORM messages is
 discussed in Sections 3.7 and 3.8.

3.1. Avoiding Fingerprinting

 There are many choices for implementing DHCPv4 messages.  Clients can
 choose to transmit a specific set of options, pick a particular
 encoding for these options, and transmit options in different orders.
 These choices can be used to fingerprint the client.
 The following sections provide guidance on the encoding of options
 and fields within the packets.  However, this guidance alone may not
 be sufficient to prevent fingerprinting from revealing the device
 type, the vendor name, or the OS type and specific version.
 Fingerprinting may also reveal whether the client is using the
 anonymity profile.
 The client intending to protect its privacy SHOULD limit the subset
 of options sent in messages to the subset listed in the remaining
 subsections.
 The client intending to protect its privacy SHOULD randomize the
 ordering of options before sending any DHCPv4 message.  If this
 random ordering cannot be implemented, the client MAY order the
 options by option code number (lowest to highest).

3.2. Client IP Address Field

 Four octets in the header of the DHCP messages carry the "Client IP
 address" (ciaddr) as defined in [RFC2131].  In DHCP, this field is
 used by the clients to indicate the address that they used
 previously, so that as much as possible the server can allocate the
 same address to them.

Huitema, et al. Standards Track [Page 10] RFC 7844 DHCP Anonymity Profiles May 2016

 There are very few privacy implications related to sending this
 address in the DHCP messages, except in the case of connecting to a
 different network than the last network connected to previously.  If
 the DHCP client somehow repeated the address used in a previous
 network attachment, monitoring services might use the information to
 tie the two network locations.  DHCP clients SHOULD ensure that the
 field is cleared when they know that the network attachment has
 changed, particularly if the link-layer address is reset by a
 device's administrator.
 The clients using the anonymity profile MUST NOT include in the
 message a Client IP address that has been obtained with a different
 link-layer address.

3.3. Requested IP Address Option

 The Requested IP address option is defined in [RFC2132] with code 50.
 It allows the client to request that a particular IP address be
 assigned.  This option is mandatory in some protocol messages per
 [RFC2131] -- for example, when a client selects an address offered by
 a server.  However, this option is not mandatory in the DHCPDISCOVER
 message.  It is simply a convenience -- an attempt to regain the same
 IP address that was used in a previous connection.  Doing so entails
 the risk of disclosing an IP address used by the client at a previous
 location or with a different link-layer address.  This risk exists
 for all forms of IP addresses, public or private, as some private
 addresses may be used in a wide scope, e.g., when an Internet Service
 Provider is using NAT.
 When using the anonymity profile, clients SHOULD NOT use the
 Requested IP address option in DHCPDISCOVER messages.  They MUST use
 the option when mandated by DHCP -- for example, in DHCPREQUEST
 messages.
 There are scenarios in which a client connecting to a network
 remembers a previously allocated address, i.e., when it is in the
 INIT-REBOOT state.  In that state, any client that is concerned with
 privacy SHOULD perform a complete four-way handshake, starting with a
 DHCPDISCOVER, to obtain a new address lease.  If the client can
 ascertain that this is exactly the same network to which it was
 previously connected, and if the link-layer address did not change,
 the client MAY issue a DHCPREQUEST to try to reclaim the current
 address.

Huitema, et al. Standards Track [Page 11] RFC 7844 DHCP Anonymity Profiles May 2016

3.4. Client Hardware Address Field

 Sixteen octets in the header of the DHCP messages carry the "Client
 hardware address" (chaddr) as defined in [RFC2131].  The presence of
 this address is necessary for the proper operation of the DHCP
 service.
 Hardware addresses, called "link-layer addresses" in many RFCs, can
 be used to uniquely identify a device, especially if they follow the
 IEEE 802 recommendations.  If the hardware address is reset to a new
 randomized value, the DHCP client SHOULD use the new randomized value
 in the DHCP messages.

3.5. Client Identifier Option

 The Client Identifier option is defined in [RFC2132] with
 option code 61.  It is discussed in detail in [RFC4361].  The purpose
 of the Client Identifier option is to identify the client in a manner
 independent of the link-layer address.  This is particularly useful
 if the DHCP server is expected to assign the same address to the
 client after a network attachment is swapped and the link-layer
 address changes.  It is also useful when the same node issues
 requests through several interfaces and expects the DHCP server to
 provide consistent configuration data over multiple interfaces.
 The considerations for hardware independence and strong client
 identity have an adverse effect on the privacy of mobile clients,
 because the hardware-independent unique identifier obviously enables
 very efficient tracking of the clients' movements.  One option would
 be to not transmit this option at all, but this may affect
 interoperability and will definitely mark the client as requesting
 anonymity, exposing it to the risks mentioned in Section 2.5.
 The recommendations in [RFC4361] are very strong, stating, for
 example, that "DHCPv4 clients MUST NOT use client identifiers based
 solely on layer two addresses that are hard-wired to the layer two
 device (e.g., the Ethernet MAC address)."  These strong
 recommendations are in fact a trade-off between ease of management
 and privacy, and the trade-off should depend on the circumstances.
 In contradiction to [RFC4361], when using the anonymity profile, DHCP
 clients MUST use client identifiers based solely on the link-layer
 address that will be used in the underlying connection.  This will
 ensure that the DHCP client identifier does not leak any information
 that is not already available to entities monitoring the network
 connection.  It will also ensure that a strategy of randomizing the
 link-layer address will not be nullified by the Client Identifier
 option.

Huitema, et al. Standards Track [Page 12] RFC 7844 DHCP Anonymity Profiles May 2016

 There are usages of DHCP where the underlying connection is a
 point-to-point link, in which case there is no link-layer address
 available to construct a non-revealing identifier.  If anonymity is
 desired in such networks, the client SHOULD pick a random identifier
 that is highly likely to be unique to the current link, using, for
 example, a combination of a local secret and an identifier of the
 connection.  The algorithm for combining secrets and identifiers, as
 described in Section 5 of [RFC7217], solves a similar problem.  The
 criteria for the generation of random numbers are stated
 in [RFC4086].

3.6. Parameter Request List Option

 The Parameter Request List (PRL) option is defined in [RFC2132] with
 option code 55.  It lists the parameters requested from the server by
 the client.  Different implementations request different parameters.
 [RFC2132] specifies that "the client MAY list the options in order of
 preference."  In practice, this means that different client
 implementations will request different parameters, in different
 orders.
 The choice of option numbers and the specific ordering of option
 numbers in the PRL can be used to fingerprint the client.  This may
 not reveal the identity of a client but may provide additional
 information such as the device type, the vendor name, or the OS type
 and specific version.
 The client intending to protect its privacy SHOULD only request a
 minimal number of options in the PRL and SHOULD also randomly shuffle
 the ordering of option codes in the PRL.  If this random ordering
 cannot be implemented, the client MAY order the option codes in the
 PRL by option code number (lowest to highest).

3.7. Host Name Option

 The Host Name option is defined in [RFC2132] with option code 12.
 Depending on implementations, the option value can carry either an
 FQDN such as "node1984.example.com" or a simple host name such as
 "node1984".  The host name is commonly used by the DHCP server to
 identify the host and also to automatically update the address of the
 host in local name services.
 FQDNs are obviously unique identifiers, but even simple host names
 can provide a significant amount of information on the identity of
 the device.  They are typically chosen to be unique in the context
 where the device is most often used.  In a context that contains a
 substantial number of devices, e.g., in a large company or a big
 university, the host name will be a pretty good identifier of the

Huitema, et al. Standards Track [Page 13] RFC 7844 DHCP Anonymity Profiles May 2016

 device, due to the specificity required to ensure uniqueness.
 Monitoring services could use that information in conjunction with
 traffic analysis and quickly derive the identity of the device's
 owner.
 When using the anonymity profile, DHCP clients SHOULD NOT send the
 Host Name option.  If they choose to send the option, DHCP clients
 MUST always send a non-qualified host name instead of an FQDN and
 MUST obfuscate the host name value.
 There are many ways to obfuscate a host name.  The construction rules
 SHOULD guarantee that a different host name is generated each time
 the link-layer address changes and that the obfuscated host name will
 not reveal the underlying link-layer address.  The construction
 SHOULD generate names that are unique enough to minimize collisions
 in the local link.  Clients MAY use the following algorithm: compute
 a secure hash of a local secret and of the link-layer address that
 will be used in the underlying connection, and then use the
 hexadecimal representation of the first 6 octets of the hash as the
 obfuscated host name.
 The algorithm described in the previous paragraph generates an easily
 recognizable pattern.  There is a potential downside to having such a
 specific name pattern for hosts that require anonymity (the "sticking
 out of the crowd" principle), as explained in Section 2.5.  For this
 reason, the above algorithm is just a suggestion.

3.8. Client FQDN Option

 The Client FQDN option is defined in [RFC4702] with option code 81.
 This option allows the DHCP clients to advertise to the DHCP server
 their FQDN, such as "mobile.example.com".  This would allow the DHCP
 server to update in the DNS the PTR record for the IP address
 allocated to the client.  Depending on circumstances, either the DHCP
 client or the DHCP server could update in the DNS the A record for
 the FQDN of the client.
 Obviously, this option uniquely identifies the client, exposing it to
 the DHCP server or to anyone listening to DHCP traffic.  In fact, if
 the DNS record is updated, the location of the client becomes visible
 to anyone with DNS lookup capabilities.
 When using the anonymity profile, DHCP clients SHOULD NOT include the
 Client FQDN option in their DHCP requests.  Alternatively, they MAY
 include a special-purpose FQDN using the same host name as in the
 Host Name option, with a suffix matching the connection-specific DNS
 suffix being advertised by that DHCP server.  Having a name in the

Huitema, et al. Standards Track [Page 14] RFC 7844 DHCP Anonymity Profiles May 2016

 DNS allows working with legacy systems that require one to be there,
 e.g., by verifying that a forward and reverse lookup succeeds with
 the same result.

3.9. UUID/GUID-Based Client Machine Identifier Option

 The UUID/GUID-based (where "UUID" means "Universally Unique
 Identifier" and "GUID" means "Globally Unique Identifier")
 Client Machine Identifier option is defined in [RFC4578] with
 option code 97.  This option is part of a set of options for the
 Intel Preboot eXecution Environment (PXE).  The purpose of the PXE
 system is to perform management functions on a device before its main
 OS is operational.  The Client Machine Identifier carries a 16-octet
 GUID that uniquely identifies the device.
 The PXE system is clearly designed for devices operating in a
 controlled environment.  The main usage of the PXE system is to
 install a new version of the operating system through a high-speed
 Ethernet connection.  The process is typically controlled from the
 user interface during the boot process.  Common sense seems to
 dictate that getting a new operating system from an unauthenticated
 server at an untrusted location is a really bad idea and that even if
 the option was available users would not activate it.  In any case,
 the option is only used in the "pre-boot" environment, and there is
 no reason to use it once the system is up and running.  Nodes
 visiting untrusted networks MUST NOT send or use the PXE options.

3.10. User and Vendor Class DHCP Options

 Vendor-identifying options are defined in [RFC2132] and [RFC3925].
 When using the anonymity profile, DHCPv4 clients SHOULD NOT use the
 Vendor-Specific Information option (code 43), the Vendor Class
 Identifier option (code 60), the V-I Vendor Class option (code 124),
 or the V-I Vendor-Specific Information option (code 125), as these
 options potentially reveal identifying information.

4. Anonymity Profile for DHCPv6

 DHCPv6 is typically used by clients in one of two scenarios: stateful
 or stateless configuration.  In the stateful scenario, clients use a
 combination of Solicit, Request, Confirm, Renew, Rebind, Release, and
 Decline messages to obtain addresses and manage these addresses.

Huitema, et al. Standards Track [Page 15] RFC 7844 DHCP Anonymity Profiles May 2016

 In the stateless scenario, clients configure addresses using a
 combination of client-managed identifiers and router-advertised
 prefixes, without involving the DHCPv6 services.  Different ways of
 constructing these prefixes have different implications on privacy,
 which are discussed in [DEFAULT-IIDs] and [RFC7721].  In the
 stateless scenario, clients use DHCPv6 to obtain network
 configuration parameters, through the Information-request message.
 The choice between the stateful and stateless scenarios depends on
 flag and prefix options published by the Router Advertisement
 messages of local routers, as specified in [RFC4861].  When these
 options enable stateless address configuration, hosts using the
 anonymity profile SHOULD use stateless address configuration instead
 of stateful address configuration, because stateless configuration
 requires fewer information disclosures than stateful configuration.
 When using the anonymity profile, DHCPv6 clients carefully select
 DHCPv6 options used in the various messages that they send.  The list
 of options that are mandatory or optional for each message is
 specified in [RFC3315].  Some of these options have specific
 implications on anonymity.  The following sections provide guidance
 on the choice of option values when using the anonymity profile.

4.1. Avoiding Fingerprinting

 There are many choices for implementing DHCPv6 messages.  As
 explained in Section 3.1, these choices can be used to fingerprint
 the client.
 The following sections provide guidance on the encoding of options.
 However, this guidance alone may not be sufficient to prevent
 fingerprinting from revealing the device type, the vendor name, or
 the OS type and specific version.  Fingerprinting may also reveal
 whether the client is using the anonymity profile.
 The client intending to protect its privacy SHOULD limit the subset
 of options sent in messages to the subset listed in the following
 sections.
 The client intending to protect its privacy SHOULD randomize the
 ordering of options before sending any DHCPv6 message.  If this
 random ordering cannot be implemented, the client MAY order the
 options by option code number (lowest to highest).

Huitema, et al. Standards Track [Page 16] RFC 7844 DHCP Anonymity Profiles May 2016

4.2. Do not send Confirm messages, unless really sure about

    the location
 [RFC3315] requires clients to send a Confirm message when they attach
 to a new link to verify whether the addressing and configuration
 information they previously received is still valid.  This
 requirement was relaxed in [DHCPv6bis].  When these clients send
 Confirm messages, they include any Identity Associations (IAs)
 assigned to the interface that may have moved to a new link, along
 with the addresses associated with those IAs.  By examining the
 addresses in the Confirm message, an attacker can trivially identify
 the previous point(s) of attachment.
 Clients interested in protecting their privacy SHOULD NOT send
 Confirm messages and instead SHOULD directly try to acquire addresses
 on the new link.  However, not sending Confirm messages can result in
 connectivity hiatus in some scenarios, e.g., roaming between two
 access points in the same wireless network.  DHCPv6 clients that can
 verify that the previous link and the current link are part of the
 same network MAY send Confirm messages while still protecting their
 privacy.  Such link identification should happen before DHCPv6 is
 used, and thus it cannot depend on the DHCPv6 information used in
 [RFC6059].  In practice, the most reliable detection of network
 attachment is through link-layer security, e.g., [IEEE8021X].

4.3. Client Identifier DHCPv6 Option

 The DHCPv6 Client Identifier option is defined in [RFC3315] with
 option code 1.  The purpose of the Client Identifier option is to
 identify the client to the server.  The content of the option is a
 DHCP Unique Identifier (DUID).  One of the primary privacy concerns
 is that a client is disclosing a stable identifier (the DUID) that
 can be used for tracking and profiling.  Three DUID formats are
 specified in [RFC3315]: link-layer address plus time (DUID-LLT),
 Vendor-assigned unique ID based on Enterprise Number, and link-layer
 address.  A fourth type, DUID-UUID, is defined in [RFC6355].
 When using the anonymity profile in conjunction with randomized
 link-layer addresses, DHCPv6 clients MUST use DUID format number 3 --
 link-layer address.  The value of the link-layer address should be
 the value currently assigned to the interface.
 When using the anonymity profile without the benefit of randomized
 link-layer addresses, clients that want to protect their privacy
 SHOULD generate a new randomized DUID-LLT every time they attach to a
 new link or detect a possible link change event.  Syntactically, this
 identifier will conform to [RFC3315], but its content is meaningless.
 The exact details are left up to implementers, but there are several

Huitema, et al. Standards Track [Page 17] RFC 7844 DHCP Anonymity Profiles May 2016

 factors that should be taken into consideration.  The DUID type
 SHOULD be set to 1 (DUID-LLT).  Hardware type SHOULD be set
 appropriately to the hardware type in question.  The link address
 embedded in the LLT SHOULD be set to a randomized value.  Time SHOULD
 be set to a random timestamp from the previous year.  Time MAY be set
 to current time, but this will reveal the fact that the DUID is newly
 generated and thus could provide information for device
 fingerprinting.  The criteria for generating highly unique random
 numbers are listed in [RFC4086].

4.3.1. Anonymous Information-request

 According to [RFC3315], a DHCPv6 client includes its client
 identifier in most of the messages it sends.  There is one exception,
 however: the client is allowed to omit its client identifier when
 sending Information-request messages.
 When using stateless DHCPv6, clients wanting to protect their privacy
 SHOULD NOT include client identifiers in their Information-request
 messages.  This will prevent the server from specifying client-
 specific options if it is configured to do so, but the need for
 anonymity precludes such options anyway.

4.4. Server Identifier Option

 When using the anonymity profile, DHCPv6 clients SHOULD use the
 Server Identifier option (code 2) as specified in [RFC3315].  Clients
 MUST only include server identifier values that were received with
 the current link-layer address, because the reuse of old values
 discloses information that can be used to identify the client.

4.5. Address Assignment Options

 When using the anonymity profile, DHCPv6 clients might have to use
 Solicit or Request messages to obtain IPv6 addresses through the
 DHCPv6 server.  In DHCPv6, the collection of addresses assigned to a
 client is identified by an IA.  Clients interested in privacy SHOULD
 request addresses using the IA for the Non-temporary Addresses option
 (IA_NA, code 3) [RFC3315].
 The IA_NA option includes an IAID parameter that identifies a unique
 IA for the interface for which the address is requested.  Clients
 interested in protecting their privacy MUST ensure that the IAID does
 not enable client identification.  They also need to conform to the
 requirement of [RFC3315] that the IAID for that IA MUST be consistent
 across restarts of the DHCPv6 client.  We interpret that as requiring
 that the IAID MUST be constant for the association, as long as the
 link-layer address remains constant.

Huitema, et al. Standards Track [Page 18] RFC 7844 DHCP Anonymity Profiles May 2016

 Clients MAY meet the privacy, uniqueness, and stability requirements
 of the IAID by constructing it as the combination of 1 octet encoding
 the interface number in the system, and the first 3 octets of the
 link-layer address.
 The clients MAY use the IA Address option (code 5) [RFC3315] but need
 to balance the potential advantage of "address continuity" versus the
 potential risk of "previous address disclosure".  A potential
 solution is to remove all stored addresses when a link-layer address
 changes and to only use the IA Address option with addresses that
 have been explicitly assigned through the current link-layer address.

4.5.1. Obtain Temporary Addresses

 [RFC3315] defines a special container (IA_TA, code 4) for requesting
 temporary addresses.  This is a good mechanism in principle, but
 there are a number of issues associated with it.  First, this is not
 a widely used feature, so clients depending solely on temporary
 addresses may lock themselves out of service.  Secondly, [RFC3315]
 does not specify any lifetime or lease length for temporary
 addresses.  Therefore, support for renewing temporary addresses may
 vary between client implementations, including no support at all.
 Finally, by requesting temporary addresses, a client reveals its
 desire for privacy and potentially risks countermeasures as described
 in Section 2.5.
 Because of these issues, clients interested in their privacy
 SHOULD NOT use IA_TA.
 The addresses obtained according to Section 4.5 are meant to be
 non-temporary, but the anonymity profile uses them as temporary, and
 they will be discarded when the link-layer address is changed.  They
 thus meet most of the use cases of the temporary addresses defined in
 [RFC4941].  Clients interested in their privacy should not publish
 their IPv6 addresses in the DNS or otherwise associate them with name
 services, and thus do not normally need two classes of addresses --
 one public, one temporary.
 The use of mechanisms to allocate several IPv6 addresses to a client
 while preserving privacy is left for further study.

Huitema, et al. Standards Track [Page 19] RFC 7844 DHCP Anonymity Profiles May 2016

4.5.2. Prefix Delegation

 The use of DHCPv6 address assignment option for Prefix Delegation
 (PD) is defined in [RFC3633].  Because current host OS
 implementations do not typically request prefixes, clients that wish
 to use DHCPv6 PD -- just like clients that wish to use any DHCP or
 DHCPv6 option that is not currently widely used -- should recognize
 that doing so will serve as a form of fingerprinting, unless or until
 the use of DHCPv6 PD by clients becomes more widespread.
 The anonymity properties of DHCPv6 PD, which uses IA_PD IAs, are
 similar to those of DHCPv6 address assignment using IA_NA IAs.  The
 IAID could potentially be used to identify the client, and a prefix
 hint sent in the IA_PD Prefix option could be used to track the
 client's previous location.  Clients that desire anonymity and never
 request more than one prefix SHOULD set the IAID value to zero, as
 authorized in Section 6 of [RFC3633], and SHOULD NOT document any
 previously assigned prefix in the IA_PD Prefix option.

4.6. Option Request Option

 The Option Request Option (ORO) is defined in [RFC3315] with
 option code 6.  It specifies the options that the client is
 requesting from the server.  The choice of requested options and the
 order of encoding of these options in the ORO can be used to
 fingerprint the client.
 The client intending to protect its privacy SHOULD only request a
 minimal subset of options and SHOULD randomly shuffle the ordering of
 option codes in the ORO.  If this random ordering cannot be
 implemented, the client MAY order the option codes in the ORO by
 option code number (lowest to highest).

4.6.1. Previous Option Values

 According to [RFC3315], the client that includes an ORO in a Solicit
 or Request message MAY additionally include instances of those
 options that are identified in the ORO, with data values as hints to
 the server about parameter values the client would like to have
 returned.
 When using the anonymity profile, clients SHOULD NOT include such
 instances of options, because old values might be used to identify
 the client.

Huitema, et al. Standards Track [Page 20] RFC 7844 DHCP Anonymity Profiles May 2016

4.7. Authentication Option

 The purpose of the Authentication option (code 11) [RFC3315] is to
 authenticate the identity of clients and servers and the contents of
 DHCPv6 messages.  As such, the option can be used to identify the
 client, so it is incompatible with the stated goal of "client
 anonymity".  DHCPv6 clients that use the anonymity profile SHOULD NOT
 use the Authentication option.  They MAY use it if they recognize
 that they are operating in a trusted environment, e.g., in a
 workplace network.

4.8. User and Vendor Class DHCPv6 Options

 When using the anonymity profile, DHCPv6 clients SHOULD NOT use the
 User Class option (code 15) or the Vendor Class option (code 16)
 [RFC3315], as these options potentially reveal identifying
 information.

4.9. Client FQDN DHCPv6 Option

 The DHCPv6 Client FQDN option is defined in [RFC4704] with
 option code 39.  This option allows the DHCPv6 clients to advertise
 to the DHCPv6 server their FQDN, such as "mobile.example.com".  When
 using the anonymity profile, DHCPv6 clients SHOULD NOT include the
 Client FQDN option in their DHCPv6 messages, because it identifies
 the client.  As explained in Section 3.8, they MAY use a local-only
 FQDN by combining a host name derived from the link-layer address and
 a suffix advertised by the local DHCPv6 server.

5. Operational Considerations

 The anonymity profiles have the effect of hiding the client identity
 from the DHCP server.  This is not always desirable.  Some DHCP
 servers provide facilities like publishing names and addresses in the
 DNS, or ensuring that returning clients get reassigned the same
 address.
 Clients using an anonymity profile may be consuming more resources.
 For example, when a client changes its link-layer address and
 requests a new IP address, the old IP address is still marked as
 leased by the server.
 Some DHCP servers will only give addresses to pre-registered MAC
 addresses, forcing clients to choose between remaining anonymous and
 obtaining connectivity.
 Implementers SHOULD provide a way for clients to control when the
 anonymity profiles are used and when standard behavior is preferred.

Huitema, et al. Standards Track [Page 21] RFC 7844 DHCP Anonymity Profiles May 2016

 Implementers MAY implement this control by tying the use of the
 anonymity profiles to that of link-layer address randomization.

6. Security Considerations

 The use of the anonymity profiles does not change the security
 considerations of the DHCPv4 or DHCPv6 protocols [RFC2131] [RFC3315].

7. References

7.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
            RFC 2131, DOI 10.17487/RFC2131, March 1997,
            <http://www.rfc-editor.org/info/rfc2131>.
 [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
            C., and M. Carney, "Dynamic Host Configuration Protocol
            for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315,
            July 2003, <http://www.rfc-editor.org/info/rfc3315>.
 [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
            Host Configuration Protocol (DHCP) version 6", RFC 3633,
            DOI 10.17487/RFC3633, December 2003,
            <http://www.rfc-editor.org/info/rfc3633>.
 [RFC4702]  Stapp, M., Volz, B., and Y. Rekhter, "The Dynamic Host
            Configuration Protocol (DHCP) Client Fully Qualified
            Domain Name (FQDN) Option", RFC 4702,
            DOI 10.17487/RFC4702, October 2006,
            <http://www.rfc-editor.org/info/rfc4702>.
 [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
            "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
            DOI 10.17487/RFC4861, September 2007,
            <http://www.rfc-editor.org/info/rfc4861>.
 [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
            Extensions for Stateless Address Autoconfiguration in
            IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
            <http://www.rfc-editor.org/info/rfc4941>.

Huitema, et al. Standards Track [Page 22] RFC 7844 DHCP Anonymity Profiles May 2016

7.2. Informative References

 [CNBC]     Weston, G., Greenwald, G., and R. Gallagher, "CBC News:
            CSEC used airport Wi-Fi to track Canadian travellers:
            Edward Snowden documents", January 2014,
            <http://www.cbc.ca/news/politics/
            csec-used-airport-wi-fi-to-track-canadian-travellers-
            edward-snowden-documents-1.2517881>.
 [DEFAULT-IIDs]
            Gont, F., Cooper, A., Thaler, D., and W. Liu,
            "Recommendation on Stable IPv6 Interface Identifiers",
            Work in Progress, draft-ietf-6man-default-iids-11,
            April 2016.
 [DHCPv6bis]
            Mrugalski, T., Ed., Siodelski, M., Volz, B., Yourtchenko,
            A., Richardson, M., Jiang, S., and T. Lemon, "Dynamic Host
            Configuration Protocol for IPv6 (DHCPv6) bis", Work in
            Progress, draft-ietf-dhc-rfc3315bis-04, March 2016.
 [GuyFawkesMask]
            Nickelsburg, M., "A brief history of the Guy Fawkes mask",
            July 2013, <http://theweek.com/articles/463151/
            brief-history-guy-fawkes-mask>.
 [IEEE8021X]
            IEEE, "IEEE Standard for Local and metropolitan area
            networks - Port-Based Network Access Control",
            IEEE 802.1X-2010, DOI 10.1109/ieeestd.2010.5409813,
            <http://ieeexplore.ieee.org/servlet/
            opac?punumber=5409757>.
 [IEEE802PRSG]
            IEEE 802 EC PRSG, "IEEE 802 EC Privacy Recommendation
            Study Group", February 2016,
            <http://www.ieee802.org/PrivRecsg/>.
 [IETFMACRandom]
            Zuniga, JC., "MAC Privacy", November 2014,
            <http://www.ietf.org/blog/2014/11/mac-privacy/>.
 [IETFTrialsAndMore]
            Bernardos, CJ., Zuniga, JC., and P. O'Hanlon, "Wi-Fi
            Internet connectivity and privacy: hiding your tracks on
            the wireless Internet", October 2015,
            <http://www.it.uc3m.es/cjbc/papers/
            pdf/2015_bernardos_cscn_privacy.pdf>.

Huitema, et al. Standards Track [Page 23] RFC 7844 DHCP Anonymity Profiles May 2016

 [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
            Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997,
            <http://www.rfc-editor.org/info/rfc2132>.
 [RFC3925]  Littlefield, J., "Vendor-Identifying Vendor Options for
            Dynamic Host Configuration Protocol version 4 (DHCPv4)",
            RFC 3925, DOI 10.17487/RFC3925, October 2004,
            <http://www.rfc-editor.org/info/rfc3925>.
 [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
            "Randomness Requirements for Security", BCP 106, RFC 4086,
            DOI 10.17487/RFC4086, June 2005,
            <http://www.rfc-editor.org/info/rfc4086>.
 [RFC4361]  Lemon, T. and B. Sommerfeld, "Node-specific Client
            Identifiers for Dynamic Host Configuration Protocol
            Version Four (DHCPv4)", RFC 4361, DOI 10.17487/RFC4361,
            February 2006, <http://www.rfc-editor.org/info/rfc4361>.
 [RFC4578]  Johnston, M. and S. Venaas, Ed., "Dynamic Host
            Configuration Protocol (DHCP) Options for the Intel
            Preboot eXecution Environment (PXE)", RFC 4578,
            DOI 10.17487/RFC4578, November 2006,
            <http://www.rfc-editor.org/info/rfc4578>.
 [RFC4704]  Volz, B., "The Dynamic Host Configuration Protocol for
            IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
            Option", RFC 4704, DOI 10.17487/RFC4704, October 2006,
            <http://www.rfc-editor.org/info/rfc4704>.
 [RFC6059]  Krishnan, S. and G. Daley, "Simple Procedures for
            Detecting Network Attachment in IPv6", RFC 6059,
            DOI 10.17487/RFC6059, November 2010,
            <http://www.rfc-editor.org/info/rfc6059>.
 [RFC6355]  Narten, T. and J. Johnson, "Definition of the UUID-Based
            DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355,
            DOI 10.17487/RFC6355, August 2011,
            <http://www.rfc-editor.org/info/rfc6355>.
 [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
            Interface Identifiers with IPv6 Stateless Address
            Autoconfiguration (SLAAC)", RFC 7217,
            DOI 10.17487/RFC7217, April 2014,
            <http://www.rfc-editor.org/info/rfc7217>.

Huitema, et al. Standards Track [Page 24] RFC 7844 DHCP Anonymity Profiles May 2016

 [RFC7618]  Cui, Y., Sun, Q., Farrer, I., Lee, Y., Sun, Q., and M.
            Boucadair, "Dynamic Allocation of Shared IPv4 Addresses",
            RFC 7618, DOI 10.17487/RFC7618, August 2015,
            <http://www.rfc-editor.org/info/rfc7618>.
 [RFC7721]  Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
            Considerations for IPv6 Address Generation Mechanisms",
            RFC 7721, DOI 10.17487/RFC7721, March 2016,
            <http://www.rfc-editor.org/info/rfc7721>.
 [RFC7819]  Jiang, S., Krishnan, S., and T. Mrugalski, "Privacy
            Considerations for DHCP", RFC 7819, DOI 10.17487/RFC7819,
            April 2016, <http://www.rfc-editor.org/info/rfc7819>.
 [RFC7824]  Krishnan, S., Mrugalski, T., and S. Jiang, "Privacy
            Considerations for DHCPv6", RFC 7824,
            DOI 10.17487/RFC7824, May 2016,
            <http://www.rfc-editor.org/info/rfc7824>.
 [WiFiRadioFingerprinting]
            Brik, V., Banerjee, S., Gruteser, M., and S. Oh, "Wireless
            Device Identification with Radiometric Signatures",
            DOI 10.1.1.145.8873, September 2008,
            <http://citeseerx.ist.psu.edu/viewdoc/
            summary?doi=10.1.1.145.8873>.

Huitema, et al. Standards Track [Page 25] RFC 7844 DHCP Anonymity Profiles May 2016

Acknowledgments

 The inspiration for this document came from discussions in the
 Perpass mailing list.  Several people provided feedback on this
 document, notably Noel Anderson, Brian Carpenter, Lorenzo Colitti,
 Stephen Farrell, Nick Grifka, Tushar Gupta, Brian Haberman, Gabriel
 Montenegro, Marcin Siodelski, Dave Thaler, Bernie Volz, and Jun Wu.

Authors' Addresses

 Christian Huitema
 Microsoft
 Redmond, WA  98052
 United States
 Email: huitema@microsoft.com
 Tomek Mrugalski
 Internet Systems Consortium, Inc.
 950 Charter Street
 Redwood City, CA  94063
 United States
 Email: tomasz.mrugalski@gmail.com
 Suresh Krishnan
 Ericsson
 8400 Decarie Blvd.
 Town of Mount Royal, QC
 Canada
 Phone: +1 514 345 7900 x42871
 Email: suresh.krishnan@ericsson.com

Huitema, et al. Standards Track [Page 26]

/data/webs/external/dokuwiki/data/pages/rfc/rfc7844.txt · Last modified: 2016/05/17 22:02 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki