AVT Working Group S. Yoon Internet-Draft J. Kim Intended status: Standards Track H. Kim Expires: November 2008 H. Jeong Y. Won Korea Information Security Agency May 2, 2008 The SEED Cipher Algorithm and Its Use with the Secure Real-time Transport Protocol (SRTP) draft-ietf-avt-seed-srtp-02 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on November 2, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This document describes the use of SEED block cipher algorithm in the Secure Real-time Transport Protocol (SRTP) for confidentiality to the Yoon, et al. Expires November 2, 2008 [Page 1] Internet-Draft SEED-SRTP May 2, 2008 RTP traffic and to the control traffic for RTP, the Real-time Transport Control Protocol (RTCP). Table of Contents 1. Introduction.................................................3 1.1. SEED....................................................3 1.2. Terminology.............................................3 2. Cipher Suite Definitions.....................................3 2.1. Mode....................................................3 2.1.1. Counter............................................3 2.1.2. Counter with CBC-MAC (CCM).........................4 2.1.3. Galois/Counter Mode (GCM)..........................4 2.2. Key Size and Number of Rounds...........................5 2.3. Block Size..............................................5 3. Security Considerations......................................5 4. References...................................................6 4.1. Normative References....................................6 4.2. Informative References..................................6 Author's Addresses..............................................7 Yoon, et al. Expires August 25, 2008 [Page 2] Internet-Draft SEED-SRTP May 2, 2008 1. Introduction This document describes the use of SEED block cipher algorithm in the Secure Real-time Transport Protocol (SRTP) for confidentiality to the RTP traffic and to the control traffic for RTP, the Real-time Transport Control Protocol (RTCP) 1.1. SEED SEED is a national industrial association standard [TTASSEED] and is widely used in South Korea for electronic commerce and financial services that are operated on wired and wireless communications. As of Sep 2003, its source code in C has been distributed to 600 businesses including academic and research institutes by KISA through e-mail. Moreover, there are several international corporations in the number of businesses. The usage of SEED has been covered the security service applications such as e-Commerce, e-mail, dedicated receiver with Broadcasting, financial service, data storage, electronic toll collection, VPN, Digital Right Management, etc. The algorithm specification and object identifiers are described in [ISOSEED] [SEED]. The SEED homepage, http://www.kisa.or.kr, contains a wealth of information about SEED, including detailed specification, evaluation report, test vectors, and so on. 1.2. Terminology 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. Cipher Suite Definitions 2.1. Mode 2.1.1. Counter Section 4.1.1 of [RFC3711] defines AES counter mode encryption, which it refers to as AES-CM. SEED counter mode is defined in a similar manner, and is denoted as SEED_CM respectively. The plaintext inputs to the block cipher are formed as in AES-CM, and the block cipher outputs are processed as in AES-CM. The only difference in the processing is that SEED-CM use SEED. SEED-CM use a 112-bit salt as an input, as does AES-CM. Yoon, et al. Expires August 25, 2008 [Page 3] Internet-Draft SEED-SRTP May 2, 2008 2.1.2. Counter with CBC-MAC (CCM) CCM is a generic authenticate-and-encrypt block cipher mode [CCM]. In this specification, CCM is used with the SEED block cipher. SEED CCM has two parameters: M indicates the authentication tag. CCM defines values of 4, 6, 8, 10, 12, 14, and 16 octets; In [RFC3711], the authentication tag size is 4 octets. Implementation MUST support M values of 4 octets. L indicates the size of the length field in octets. CCM defines values of L between 2 octets and 8 octets. Implementations MUST support an L value of 4 octets, which accommodates a full Jumbogram [JUMBO]; however, the length includes all of the encrypted data. SEED CCM has four inputs: Key An encryption key K suitable for the block cipher. SEED supports 128-bit key, and implementations MUST support this key size. Nonce Section 4.1.1 of [RFC3711] defines the IV that is necessary to construct the sequence of counter blocks used by counter mode to generate the key stream. The SEED counter block is 16 octets. Payload The payload of the RTP packet. The payload MUST NOT be longer than 4,294,967,295 octets, which is the maximum size of a Jumbogram. AAD The header of the RTP packet. CCM does not allow additional authenticated data (AAD) to be longer than 18,446,744,073,709,551,615 octets. 2.1.3. Galois/Counter Mode (GCM) GCM is a block cipher mode of operation providing both confidentiality and data origin authentication [GCM]. GCM is used with the SEED block cipher. Four inputs for SEED GCM are described in Section 2.1.2 Yoon, et al. Expires August 25, 2008 [Page 4] Internet-Draft SEED-SRTP May 2, 2008 2.2. Key Size and Number of Rounds SEED supports 128-bit key and has the 16-round Feistel structure. 2.3. Block Size SEED uses a block size of 16 octets (128 bits). 3. Security Considerations No security problem has been found on SEED. SEED is secure against all known attacks including Differential cryptanalysis, linear cryptanalysis, and related key attacks. The best known attack is only an exhaustive search for the key. For further security considerations, the reader is encouraged to read [CRYPTREC] and [SEED-EVAL]. Yoon, et al. Expires August 25, 2008 [Page 5] Internet-Draft SEED-SRTP May 2, 2008 4. References 4.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [SEED] Park, J., Lee, S., Kim, J., and J. Lee, "The SEED Encryption Algorithm", RFC 4009, February 2005. [RFC3711] M. Baugher, D. McGrew, M. Naslund, E.Carrara, K. Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC 3711, March 2004. 4.2. Informative References [CRYPTREC] Information-technology Promotion Agency (IPA), Japan, CRYPTREC. "SEED Evaluation Report", February, 2002. http://www.kisa.or.kr/kisa/seed/data/Document_pdf/SEED_Ev aluation_Report_by_CRYPTREC.pdf [ISOSEED] ISO/IEC JTC 1/SC 27, "National Body contributions on NP 18033 "Encryption Algorithms" in Response to SC 27 N2563 (ATT.3 Korea Contribution)", ISO/IEC JTC 1/SC 27 N2656r1 (n2656_3.zip), October, 2000. [SEED-EVAL] KISA, "Self Evaluation Report", http://www.kisa.or.kr/kisa/seed/data/Document_pdf/SEED_Ev aluation_Report_by_CRYPTREC.pdf [TTASSEED] Telecommunications Technology Association (TTA), South Korea, "128-bit Symmetric Block Cipher (SEED)", TTAS.KO- 12.0004, September, 1998 (In Korean) http://www.tta.or.kr/English/new/main/index.htm [JUMBO] Borman, D., Deering, S., and R. Hinden, "IPv6 Jumbograms", RFC 2675, August 1999. [CCM] Whiting, D., Housley, R., and N. Ferguson, "Counter with CBC-MAC (CCM), RFC 3610, September 2003. [GCM] Dworkin, M., "NIST Special Publication 800-38D: Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC.", U.S. National Institute of Standards and Technology http://csrc.nist.gov/Publications/nistpubs/800-38D/SP- 800-38D.pdf Yoon, et al. Expires August 25, 2008 [Page 6] Internet-Draft SEED-SRTP May 2, 2008 Author's Addresses Seokung Yoon Korea Information Security Agency 78, Karak-dong, Songpa-Gu, Seoul 138-160, KOREA Phone: +82-2-405-5361 Email: seokung@kisa.or.kr Joongman Kim Korea Information Security Agency 78, Karak-dong, Songpa-Gu, Seoul 138-160, KOREA Phone: +82-2-405-5314 Email: seopo@kisa.or.kr Hyun Kim Korea Information Security Agency 78, Karak-dong, Songpa-Gu, Seoul 138-160, KOREA Phone: +82-2-405-5355 Email: hkim@kisa.or.kr Hyuncheol Jeong Korea Information Security Agency 78, Karak-dong, Songpa-Gu, Seoul 138-160, KOREA Phone: +82-2-405-5360 Email: hcjung@kisa.or.kr Yoojae Won Korea Information Security Agency 78, Karak-dong, Songpa-Gu, Seoul 138-160, KOREA Phone: +82-2-405-5300 Email: yjwon@kisa.or.kr Yoon, et al. Expires August 25, 2008 [Page 7] Internet-Draft SEED-SRTP May 2, 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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