AVT Working Group Seokung Yoon Internet Draft Joongman Kim Expires: January 2008 Yoojae Won Korea Information Security Agency July 2, 2007 The SEED Cipher Algorithm and Its Use with the Secure Real-time Transport Protocol (SRTP) draft-seokung-avt-seed-srtp-00.txt 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 January 2, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document describes the use of SEED block cipher algorithm in the Secure Real-time Transport Protocol [3] for confidentiality to the RTP traffic and to the control traffic for RTP, the Real-time Transport Control Protocol (RTCP). Yoon, et al. Expires January 2, 2008 [Page 1] Internet-Draft AVT-SEED-SRTP July 2, 2007 Table of Contents 1. Introduction..................................................2 1.1. SEED.....................................................2 1.2. Terminology..............................................3 2. The SEED Cipher Algorithm.....................................3 2.1. Mode.....................................................3 2.2. Key Size and Number of Rounds............................3 2.3. Block Size and Padding...................................3 2.4. Performance..............................................3 3. Security Considerations.......................................3 4. IANA Considerations...........................................4 5. References....................................................4 5.1. Normative References.....................................4 5.2. Informative References...................................4 Author's Addresses...............................................5 Intellectual Property Statement..................................5 Disclaimer of Validity...........................................6 1. Introduction 1.1. SEED SEED [2] is a national industrial association standard [7] and is widely used in South Korea for electronic commerce and financial services that are operated on wired and wireless communications. SEED is a 128-bit symmetric key block cipher that had been developed by KISA(Korea Information Security Agency) and a group of experts since 1998. The input/output block size of SEED is 128-bit and the key length is also 128-bit. SEED has the 16-round Feistel structure. A 128-bit input is divided into two 64-bit blocks and the right 64- bit block is an input to the round function with a 64-bit subkey generated from the key scheduling. SEED is easily implemented in various software and hardware because it is designed to increase the efficiency of memory storage and the simplicity in generating keys without degrading the security of the algorithm. In particular, it can be effectively adapted to a computing environment with restricted resources such as mobile devices, smart cards and so on. Yoon, et al. Expires January 2, 2008 [Page 2] Internet-Draft AVT-SEED-SRTP July 2, 2007 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 RFC-2119 [1]. 2. The SEED Cipher Algorithm The algorithm specification and object identifiers are described in [5] [3]. The SEED homepage, http://www.kisa.or.kr/seed/seed_eng.html, contains a wealth of information about SEED, including a detailed specification, evaluation report, test vectors, and so on. 2.1. Mode This document specifies the use of the SEED cipher in the CBC (Cipher Block Chaining) mode. This mode requires an Initialization Vector IV) that is the same size as the block size. The IV MUST be chosen at random and MUST be unpredictable. 2.2. Key Size and Number of Rounds SEED supports 128-bit key and has the 16-round Feistel structure. 2.3. Block Size and Padding SEED uses a block size of 16 octets (128 bits). Padding is required by SEED to maintain a 16-octet (128-bit) blocksize. Padding must be added such that the data to be encrypted has a length that is a multiple of 16 octets. 2.4. Performance Performance figures of SEED are available at http://www.kisa.or.kr/seed/seed_eng.html. 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 Yoon, et al. Expires January 2, 2008 [Page 3] Internet-Draft AVT-SEED-SRTP July 2, 2007 an exhaustive search for the key (by [4]). For further security considerations, the reader is encouraged to read [4], [5], and [6]. 4. IANA Considerations 5. References 5.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] KISA, "SEED Algorithm Specification", http://www.kisa.or.kr/seed/seed_eng.html. [3] M. Baugher, D. McGrew, M. Naslund, E.Carrara, K. Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC 3711, March 2004. 5.2. Informative References [4] Information-technology Promotion Agency (IPA), Japan, CRYPTREC. "SEED Evaluation Report", February, 2002 http://www.kisa.or.kr/seed/seed_eng.html. [5] 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. [6] KISA, "Self Evaluation Report", http://www.kisa.or.kr/seed/seed_eng.html. [7] 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. Yoon, et al. Expires January 2, 2008 [Page 4] Internet-Draft AVT-SEED-SRTP July 2, 2007 Author's Addresses Seokung Yoon Korea Information Security Agency 78, Karak-dong, Songpa-Gu Seoul 138-160 KOREA Phone: +82-2-405-5361 FAX : +82-2-405-5319 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 FAX : +82-2-405-5319 Email: seopo@kisa.or.kr Yoojae Won Korea Information Security Agency 78, Karak-dong, Songpa-Gu Seoul 138-160 KOREA Phone: +82-2-405-5360 FAX : +82-2-405-5319 Email: yjwon@kisa.or.kr Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this Yoon, et al. Expires January 2, 2008 [Page 5] Internet-Draft AVT-SEED-SRTP July 2, 2007 specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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. Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Yoon, et al. Expires January 2, 2008 [Page 6]