HTTP/1.1 200 OK Date: Tue, 09 Apr 2002 04:14:15 GMT Server: Apache/1.3.20 (Unix) Last-Modified: Wed, 02 Jul 1997 15:22:00 GMT ETag: "2f5411-4fa7-33ba7218" Accept-Ranges: bytes Content-Length: 20391 Connection: close Content-Type: text/plain Network Working Group R. Thayer Internet Draft N. Doraswamy Category: Informational R. Glenn Expire in six months July 1997 IP Security Document Roadmap Status of This Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress.'' To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). This memo provides information for the Internet community. This memo does not specify an Internet standard. Distribution of this memo is unlimited. Abstract The IPsec protocol suite is used to provide privacy and authentication services at the IP layer. Several documents are used to describe this protocol suite. The interrelationship and organization of the various documents covering the IPsec protocol are discussed here. An explanation of what to find in which document, and what to include in new Cipher and Authenticator documents are described. Thayer, Doraswamy, Glenn [Page 1] INTERNET DRAFT July 1997 Expires January 1998 Contents Status of This Memo .................................................1 Abstract ............................................................1 Contents ............................................................2 1. Introduction .....................................................3 2. Interrelationship of IPsec Documents .............................3 3. Keying Material ..................................................5 4. Recommended Content of Cipher and Authenticator Documents ........5 4.1 Cipher and Authenticator ........................................5 4.2 Cipher ..........................................................6 4.3 Authenticator ...................................................7 5. Security Considerations ..........................................8 6. Acknowledgments ..................................................8 7. References .......................................................9 8. Author's Addresses ...............................................9 Thayer, Doraswamy, Glenn [Page 2] INTERNET DRAFT July 1997 Expires January 1998 1. Introduction This document is intended to provide guidelines for the development of collateral specifications describing the use of new Cipher and Authenticator algorithms with the ESP protocol, described in [ESP] and new Authenticator algorithms used with the AH protocol, described in [AH]. ESP and AH are part of the IP Security architecture described in [Arch]. There is a requirement for a well-known procedure that can be used to add new cipher algorithms or authenticator algorithms to ESP and AH, not only while the initial document set is undergoing development but after the base documents have achieved RFC status. Following the guidelines discussed below simplifies adding new algorithms and reduces that amount of redundant documentation. The goal in writing a new ESP or AH algorithm document is to concentrate on the application of the specific algorithm. General ESP and AH concepts, definitions, and issues are covered in the ESP and AH documents. The algorithms themselves are not described in these documents. This gives us the capability to add new algorithms and also specify how any given algorithm might interact with other algorithms. The intent is to achieve the goal of avoiding duplication of information and excessive numbers of documents, the so-called "draft explosion" effect. 2. Interrelationship of IPsec Documents The documents describing the set of IPsec protocols are divided into seven groups. This is illustrated in Figure 1. There is a main Architecture document which broadly covers the general concepts, security requirements, definitions, and mechanisms defining IPsec technology. There is an ESP Protocol document and an AH Protocol document which covers the packet format and general issues regarding the respective protocols. These protocol documents also contain default values if appropriate, such as the default padding contents, and mandatory to implement algorithms. These documents dictate some of the values in the Domain Of Interpretation document [DOI]. Note the DOI document is itself part of the IANA Assigned Numbers mechanism and so the values described in the DOI are well-known. See [DOI] for more information on the mechanism. The "Cipher" document set, shown on the left, is the set of documents describing how various ciphers are used for ESP. These documents are intended to fit in this roadmap, and should avoid overlap with the ESP protocol document and with the Authenticator documents. Examples of this document are the [DES-1829], [DES-Detroit], [3DES], or [CAST] documents. When these or other Ciphers are used for ESP, the DOI document has to indicate certain values, such as Cipher type, so these documents provide input to the DOI. The "Authenticator" document set, shown on the right, is the set of documents describing how various authenticator algorithms are used Thayer, Doraswamy, Glenn [Page 3] INTERNET DRAFT July 1997 Expires January 1998 for both ESP and AH. These documents are intended to fit in this roadmap, and should avoid overlap with the AH protocol document and with the Cipher documents. Examples of this document are the [HMAC- MD5], and [HMAC-SHA-1] documents. When these or other algorithms are used for either ESP or AH, the DOI document has to indicate certain values, such as algorithm type, so these documents provide input to the DOI. The "Key Management Documents", shown at the bottom, are the documents describing the IETF standards-track key management schemes. These documents provide certain values for the DOI also. Note that issues of key management should be indicated here and not in, for example, the ESP and AH protocol documents. Currently this box represents [ISAKMP], [Oakley], and [Resolution]. The DOI document, shown in the middle, contains values needed for the other documents to relate to each other. This includes for example Cipher algorithms, Authenticator algorithms, and operational parameters such as key lifetimes. +--------------+ | Architecture | +--------------+ v v +<-<-<-<-+ +->->->->+ v v +----------+ +----------+ | ESP | | AH | | PROTOCOL | | PROTOCOL | +----------+ +----------+ v v v v v +->->->->->->->->+ v v v v v v v v v v v v v +--------+ +---------------+ v v | +--------+ | +---------------+ v v | | | | | | v v +-| Cipher | +-| Authenticator | v v +--------+ +---------------+ v v v v v v v +-----+ v v +>->->->-+->->->->| DOI |<-<-<-<-+-<-<-<-<-+ +-----+ ^ ^ +------------+ | KEY | | MANAGEMENT | +------------+ Figure 1. IPsec Document Roadmap. Thayer, Doraswamy, Glenn [Page 4] INTERNET DRAFT July 1997 Expires January 1998 3. Keying Material Describing the cipher and authenticator algorithms in different docu- ments raises the issue of how the key management protocols knows the required keying material length for the desired algorithms when used together with ESP. It also raises the issue of how to divide the keying material. This is known as the "slicing and dicing" informa- tion. Each cipher and authenticator document should specify their respec- tive key lengths. The key management protocols should use the length of the keys specified in the cipher and authenticator documents to generate the keying material of required length. The ESP protocol document is responsible for specifying how the keys are extracted from the keying material (sliced and diced). For exam- ple, it should specify if the cipher or the authenticator algorithm uses the first n-bits in the provided keying material. The AH proto- col document has no such requirement. [Editor's Note: This paragraph is still under contention and will be modified once the location of the key derivation mechanism is known]. 4. Recommended Content of Cipher and Authenticator Documents The document describing how a specific cipher or authenticator is used should contain information appropriate to that cipher or authen- ticator. This section enumerates what information should be pro- vided. It is the intention of the document roadmap that: . General protocol information goes in the respective ESP or AH protocol documents. . Key management information goes in the key management documents. . Assigned values and constants go in the DOI document. Cipher and Authenticator algorithms require some set of optional parameters or have optional modes of operation (e.g. IVs, authentica- tor lengths, and key lengths). To help eliminate some complexity involved with key management having to negotiate large numbers of algorithm-specific parameters, Cipher and Authenticator documents will select fixed values for these parameters when it is deemed technically reasonable and feasible. Note, the following information is intended as a general guideline only. 4.1 Cipher and Authenticator This section describes the information that should be included in both Cipher and Authenticator documents. Keying Material . Size of keys, including minimum, maximum, recommended and/or required sizes. Note: the security considerations section should address any weakness in specific sizes. Thayer, Doraswamy, Glenn [Page 5] INTERNET DRAFT July 1997 Expires January 1998 . Format of keying material. . Known weak keys or references to documentation on known weak keys. . Recommended or required processing of input keying material such as parity generation or checking. . Requirements and/or recommendations on how often the keying material should be refreshed. Performance Considerations . Any available estimates on performance of this algorithm. . Any available comparison data (e.g., compared against DES or MD5). . Input size or other considerations that could improve or degrade performance. ESP Environmental Considerations . Any known issues regarding interactions between this algorithm and other aspects of ESP, such as use of certain authentication schemes. Note: As new authentication and cipher algorithms are applied to ESP, the later documents will be required to address interactions with previously specified algorithms. Payload Content and Format Description . Specification of size, placement, and content of algorithm-specific fields not defined in the ESP or AH protocol documents (e.g., IV). Security Considerations . Discuss any known attacks. . Discuss any known common implementation pitfalls, such as use of weak random number generators. . Discuss any relevant validation procedures, such as test vectors. 4.2 Cipher This section describes the information that should be included in Cipher documents. Cipher Description . General information how this cipher algorithm is to be used in ESP. . Description of background material and formal algorithm description. . Features of this cipher to be used by ESP, including encryption and/or authentication. . Mention of any availability issues such as Intellectual Property considerations. . References, in IETF style, to background material such as FIPS documents. Algorithm Modes of Operation . Description of how the algorithm is operated, whether it is block mode or streaming mode or other. . Requirements for input or output block format. . Padding requirements of this algorithm. Note: there is a default for padding, specified in the base ESP document, so this is only Thayer, Doraswamy, Glenn [Page 6] INTERNET DRAFT July 1997 Expires January 1998 needed if the default cannot be used. . Any algorithm-specific operating parameters, such as number of rounds. . Identify optional parameters and optional methods of operation and pick reasonable fixed values and methods with explicit technical explanations. . Identify those optional parameters in which values and methods should remain optional with explicit technical explanations on why fixed values and methods should not be used. . Defaults and mandatory ranges on algorithm-specific optional parameters that could not be fixed. 4.3 Authenticator This section describes the information that should be included in Authenticator documents. In most cases, an authenticator algorithm will operate the same whether it is used for ESP or AH. This should be represented in a single authenticator algorithm document. Authenticator Description . General information on how this authenticator algorithm is to be used with ESP and AH. . Description of background material and formal algorithm description. . Features of this authenticator. . Mention of any availability issues such as Intellectual Property considerations. . References, in IETF style, to background material such as FIPS documents and definitive descriptions of underlying algorithms. Algorithm Modes of Operation . Description of how the algorithm is operated. . Algorithm-specific operating parameters, such as number of rounds, and input or output block format. . Implicit and explicit padding requirements of this algorithm. Note: There is a default method for padding of the authenticator field specified in the AH protocol document. This is only needed if the default cannot be used. . Identify optional parameters and optional methods of operation and pick reasonable fixed values and methods with explicit technical explanations. . Identify those optional parameters in which values and methods should remain optional with explicit technical explanations on why fixed values and methods should not be used. . Defaults and mandatory ranges on algorithm-specific optional parameters that could not be fixed. . Authenticator comparison criteria for this algorithm. Note: There is a default method for verifying the authenticator specified in the AH protocol document. This is only needed if the default cannot be used (e.g. when using a signed hash). Thayer, Doraswamy, Glenn [Page 7] INTERNET DRAFT July 1997 Expires January 1998 5. Security Considerations This document provides a roadmap and guidelines for writing cipher and authenticator documents. The reader SHOULD follow all the secu- rity procedures and guidelines described in the IPsec Architecture, ESP, AH, cipher and authenticator documents. Note that many cipher algorithms are not considered secure if they are not used with some sort of authentication mechanism. 6. Acknowledgments Several Internet drafts were referenced in writing this document. Depending on where the documents are on (or off) the IETF standards track these may not be available through the IETF RFC repositories. In certain cases the reader may want to know what version of these documents were referenced. These documents are: . ARCH: draft-ietf-ipsec-arch-sec-01.txt. . DES-Detroit: this is the ANX Workshop style of ESP, based on the Hughes draft as modified by Cheryl Madson and published on the ANX mailing list. . DES-1829: this is Bill Simpson's DES-CBC for ESP document, to be published as draft-simpson-esp-des1-v2-01.txt. . 3DES: this is . . CAST: this is draft-ietf-ipsec-esp-cast-128-cbc-00.txt, as revised to relate to this document. . DOI: draft-ietf-ietf-doi-02.txt. . ESP: draft-ietf-ipsec-esp-04.txt, mailed to the IETF mailing list in May/June 1997. . AH: draft-ietf-ipsec-auth-05.txt, mailed to the IETF mailing list in May/June 1997. . HUGHES: this is draft-ietf-ipsec-esp-des-md5-03.txt . ISAKMP: There are three documents describing ISAKMP. These are draft-ietf-ipsec-isakmp-07.txt, draft-ietf-ipsec-isakmp-oakley- 03.txt, and draft-ietf-ipsec-ipsec-doi-02.txt. Thayer, Doraswamy, Glenn [Page 8] INTERNET DRAFT July 1997 Expires January 1998 7. References [3DES] Triple-DES for ESP, RFC-xxxx. [ARCH] Atkinson, R., "Security Architecture for the Internet Protocol", RFC-1825, Naval Research Laboratory, July 1995. [CAST] CAST for ESP, RFC-xxxx. [DES-Detroit] DES for ESP, Detroit dialect, RFC-xxxx. [DES-1829] DES for ESP, 1829-Compatible mode, RFC-xxxx. [DOI] IP Security Domain of Interpretation, RFC-xxxx. [ESP] Karn, P., Metzger, P., and W. Simpson, "The ESP DES-CBC Transform", RFC 1829, Qualcomm, Inc., Piermont, Daydreamer, August 1995. [HMAC] Krawczyk, K., Bellare, M., and Canetti R., "HMAC: Keyed-Hashing for Message Authentication", RFC-2104, February 1997. [HMAC-MD5] Madson, C., Glenn, R., "The Use of HMAC-MD5 within ESP and AH", draft-ietf-ipsec-ff-auth-hmac-sha-1-00.txt, June 1997. [HMAC-SHA-1] Madson, C., Glenn, R., "The Use of HMAC-SHA-1 within ESP and AH", draft-ietf-ipsec-ff-auth-hmac-sha-1-00.txt, June 1997. 8. Author's Addresses Rodney Thayer Sable Technology Corporation 246 Walnut Street Newton, Massachusetts 02160 Naganand Doraswamy Bay Networks e-mail: naganand@baynetworks.com Rob Glenn NIST e-mail: rob.glenn@nist.gov Thayer, Doraswamy, Glenn [Page 9]