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rfc:rfc3365

Network Working Group J. Schiller Request for Comments: 3365 Massachusetts Institute of Technology BCP: 61 August 2002 Category: Best Current Practice

                 Strong Security Requirements for
         Internet Engineering Task Force Standard Protocols

Status of this Memo

 This document specifies an Internet Best Current Practices for the
 Internet Community, and requests discussion and suggestions for
 improvements.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

 It is the consensus of the IETF that IETF standard protocols MUST
 make use of appropriate strong security mechanisms.  This document
 describes the history and rationale for this doctrine and establishes
 this doctrine as a best current practice.

Table of Contents

 1.  Introduction. . . . . . . . . . . . . . . . . . . . . . . . .   2
 2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
 3.  Security Services . . . . . . . . . . . . . . . . . . . . . .   2
 4.  The Properties of the Internet. . . . . . . . . . . . . . . .   3
 5.  IETF Security Technology. . . . . . . . . . . . . . . . . . .   3
 6.  The Danvers Doctrine. . . . . . . . . . . . . . . . . . . . .   4
 7.  MUST is for Implementors. . . . . . . . . . . . . . . . . . .   5
 8.  Is Encryption a MUST? . . . . . . . . . . . . . . . . . . . .   5
 9.  Crypto Seems to Have a Bad Name . . . . . . . . . . . . . . .   6
 10. Security Considerations . . . . . . . . . . . . . . . . . . .   6
 11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
 12. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
 13. Author's Address  . . . . . . . . . . . . . . . . . . . . . .   7
 14. Full Copyright Statement  . . . . . . . . . . . . . . . . . .   8

Schiller Best Current Practice [Page 1] RFC 3365 Encryption Security Requirements August 2002

1. Introduction

 The purpose of this document is to document the IETF consensus on
 security requirements for protocols as well as to provide the
 background and motivation for them.
 The Internet is a global network of independently managed networks
 and hosts.  As such there is no central authority responsible for the
 operation of the network.  There is no central authority responsible
 for the provision of security across the network either.
 Security needs to be provided end-to-end or host to host.  The IETF's
 security role is to ensure that IETF standard protocols have the
 necessary features to provide appropriate security for the
 application as it may be used across the Internet.  Mandatory to
 implement mechanisms should provide adequate security to protect
 sensitive business applications.

2. Terminology

 Although we are not defining a protocol standard in this document we
 will use the terms MUST, MAY, SHOULD and friends in the ways defined
 by [RFC2119].

3. Security Services

 [RFC2828] provides a comprehensive listing of internetwork security
 services and their definitions.  Here are three essential
 definitions:
  • Authentication service: A security service that verifies an

identity claimed by or for an entity, be it a process, computer

   system, or person.  At the internetwork layer, this includes
   verifying that a datagram came from where it purports to originate.
   At the application layer, this includes verifying that the entity
   performing an operation is who it claims to be.
  • Data confidentiality service: A security service that protects

data against unauthorized disclosure to unauthorized individuals or

   processes.  (Internet Standards Documents SHOULD NOT use "data
   confidentiality" as a synonym for "privacy", which is a different
   concept.  Privacy refers to the right of an entity, normally a
   person, acting in its own behalf, to determine the degree to which
   it will interact with its environment, including the degree to
   which the entity is willing to share information about itself with
   others.)

Schiller Best Current Practice [Page 2] RFC 3365 Encryption Security Requirements August 2002

  • Data integrity service: A security service that protects against

unauthorized changes to data, including both intentional change

   (including destruction) and accidental change (including loss), by
   ensuring that changes to data are detectable.

4. Some Properties of the Internet

 As mentioned earlier, the Internet provides no inherent security.
 Enclaves of networking exist where users believe that security is
 provided by the environment itself.  An example would be a company
 network not connected to the global Internet.
 One might imagine that protocols designed to operate in such an
 enclave would not require any security services, as the security is
 provided by the environment.
 History has shown that applications that operate using the TCP/IP
 Protocol Suite wind up being used over the Internet.  This is true
 even when the original application was not envisioned to be used in a
 "wide area" Internet environment.  If an application isn't designed
 to provide security, users of the application discover that they are
 vulnerable to attack.

5. IETF Security Technology

 The IETF has several security protocols and standards.  IP Security
 (IPsec [RFC2411]), Transport Layer Security (TLS [RFC2246]) are two
 well known protocols.  Simple Authentication and Security Layer (SASL
 [RFC2222] and the Generic Security Service Application Programming
 Interface (GSSAPI [RFC2743]) provide services within the context of a
 "host" protocol.  They can be viewed as "toolkits" to use within
 another protocol.
 One of the critical choices that a protocol designer must make is
 whether to make use of one of the existing protocols, engineer their
 own protocol to use one of the standard tools or do something
 completely different.
 There is no one correct answer for all protocols and designers really
 need to look at the threats to their own protocol and design
 appropriate counter-measures.  The purpose of the "Security
 Considerations" Section required to be present in an RFC on the
 Internet Standards Track is to provide a place for protocol designers
 to document the threats and explain the logic to their security
 design.

Schiller Best Current Practice [Page 3] RFC 3365 Encryption Security Requirements August 2002

6. The Danvers Doctrine

 At the 32cd IETF held in Danvers, Massachusetts during April of 1995
 the IESG asked the plenary for a consensus on the strength of
 security that should be provided by IETF standards.  Although the
 immediate issue before the IETF was whether or not to support
 "export" grade security (which is to say weak security) in standards
 the question raised the generic issue of security in general.
 The overwhelming consensus was that the IETF should standardize on
 the use of the best security available, regardless of national
 policies.  This consensus is often referred to as the "Danvers
 Doctrine".
 Over time we have extended the interpretation of the Danvers Doctrine
 to imply that all IETF protocols should operate securely.  How can
 one argue against this?
 Since 1995 the Internet has increasingly come under attack from
 various malicious actors.  In 2000 significant press coverage was
 devoted to Distributed Denial of Service attacks.  However many of
 these attacks were launched by first compromising an Internet
 connected computer system.  Usually many systems are compromised in
 order to launch a significant distributed attack.
 A conclusion we can draw from all of this is that if we fail to
 provide secure protocols, then the Internet will become less useful
 in providing an international communications infrastructure, which
 appears to be its destiny.
 One of the continuing arguments we hear against building security
 into protocols is the argument that a given protocol is intended only
 for use in "protected" environments where security will not be an
 issue.
 However it is very hard to predict how a protocol will be used in the
 future.  What may be intended only for a restricted environment may
 well wind up being deployed in the global Internet.  We cannot wait
 until that point to "fix" security problems.  By the time we realize
 this deployment, it is too late.
 The solution is that we MUST implement strong security in all
 protocols to provide for the all too frequent day when the protocol
 comes into widespread use in the global Internet.

Schiller Best Current Practice [Page 4] RFC 3365 Encryption Security Requirements August 2002

7. MUST is for Implementors

 We often say that Security is a MUST implement.  It is worth noting
 that there is a significant different between MUST implement and MUST
 use.
 As mentioned earlier, some protocols may be deployed in secure
 enclaves for which security isn't an issue and security protocol
 processing may add a significant performance degradation.  Therefore
 it is completely reasonable for security features to be an option
 that the end user of the protocol may choose to disable.  Note that
 we are using a fuzzy definition of "end user" here.  We mean not only
 the ultimate end user, but any deployer of a technology, which may be
 an entire enterprise.
 However security must be a MUST IMPLEMENT so that end users will have
 the option of enabling it when the situation calls for it.

8. Is Encryption a MUST?

 Not necessarily.  However we need to be a bit more precise here.
 Exactly what security services are appropriate for a given protocol
 depends heavily on the application it is implementing.  Many people
 assume that encryption means confidentiality.  In other words the
 encryption of the content of protocol messages.
 However there are many applications where confidentiality is not a
 requirement, but authentication and integrity are.
 One example might be in a building control application where we are
 using IP technology to operate heat and vent controls.  There is
 likely no requirement to protect the confidentiality of messages that
 instruct heat vents to open and close.  However authentication and
 integrity are likely important if we are to protect the building from
 a malicious actor raising or lowering the temperature at will.
 Yet we often require cryptographic technology to implement
 authentication and integrity of protocol messages.  So if the
 question is "MUST we implement confidentiality?" the answer will be
 "depends".  However if the question is "MUST we make use of
 cryptographic technology?" the answer is "likely".

Schiller Best Current Practice [Page 5] RFC 3365 Encryption Security Requirements August 2002

9. Crypto Seems to Have a Bad Name

 The mention of cryptographic technology in many IETF forums causes
 eyes to glaze over and resistance to increase.
 Many people seem to associate the word "cryptography" with concerns
 such as export control and performance.  Some just plain do not
 understand it and therefore shy away from its use.  However many of
 these concerns are unfounded.
 Today export control, at least from most of the developed world, is
 becoming less of a concern.  And even where it is a concern, the
 concern is not over cryptography itself but in its use in providing
 confidentiality.
 There are performance issues when you make use of cryptographic
 technology.  However we pride ourselves in the IETF as being
 engineers.  It is an engineering exercise to figure out the
 appropriate way to make use of cryptographic technology so as to
 eliminate or at least minimize the impact of using cryptography
 within a given protocol.
 Finally, as to understanding cryptography, you don't have to.  In
 other words, you do not need to become a cryptographer in order to
 effectively make use of cryptographic technology.  Instead you make
 use of existing well understood ciphers and cipher suites to solve
 the engineering problem you face.
 One of the goals that we have in the Security Area of the IETF is to
 come up with guides so that protocol implementers can choose
 appropriate technology without having to understand the minutiae.

10. Security Considerations

 This document is about the IETF's requirement that security be
 considered in the implementation of protocols.  Therefore it is
 entirely about security!

11. Acknowledgements

 The author would like to acknowledge the participation of the
 Security Area Advisory Group and in particular Rob Shirey, Ran
 Atkinson, Steve Bellovin, Marc Blanchet, Steve Kent, Randy Bush, Dave
 Crocker, Stephen Farrell, Paul Hoffman, Russ Housley, Christian
 Huitema, Melinda Shore, Adam Shostack and Kurt D. Zeilenga.

Schiller Best Current Practice [Page 6] RFC 3365 Encryption Security Requirements August 2002

12. References

 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2222] Myers, J., "Simple Authentication and Security Layer
           (SASL)", RFC 2222, October 1997.
 [RFC2411] Thayer, R., Doraswamy, N. and R. Glenn, "IP Security
           Document Roadmap", RFC 2411, November 1998.
 [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
           RFC 2246, January 1999.
 [RFC2743] Linn, J., "Generic Security Service Application Program
           Interface Version 2, Update 1.", RFC 2743, January 2000.
 [RFC2828] Shirey, R., "Internet Security Glossary", FYI 36, RFC 2828,
           May 2000.

13. Author's Address

 Jeffrey I. Schiller
 MIT Room W92-190
 77 Massachusetts Avenue
 Cambridge, MA 02139-4307
 USA
 Phone: +1 (617) 253-8400
 EMail: jis@mit.edu

Schiller Best Current Practice [Page 7] RFC 3365 Encryption Security Requirements August 2002

14. Full Copyright Statement

 Copyright (C) The Internet Society (2002).  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 assigns.
 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.

Schiller Best Current Practice [Page 8]

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