1 2 3 4 5 6 7Network Working Group M. Horowitz 8<draft-ietf-cat-kerb-des3-hmac-sha1-00.txt> Cygnus Solutions 9Internet-Draft November, 1996 10 11 12 Triple DES with HMAC-SHA1 Kerberos Encryption Type 13 14Status of this Memo 15 16 This document is an Internet-Draft. Internet-Drafts are working 17 documents of the Internet Engineering Task Force (IETF), its areas, 18 and its working groups. Note that other groups may also distribute 19 working documents as Internet-Drafts. 20 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as ``work in progress.'' 25 26 To learn the current status of any Internet-Draft, please check the 27 ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow 28 Directories on ds.internic.net (US East Coast), nic.nordu.net 29 (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific 30 Rim). 31 32 Distribution of this memo is unlimited. Please send comments to the 33 <cat-ietf@mit.edu> mailing list. 34 35Abstract 36 37 This document defines a new encryption type and a new checksum type 38 for use with Kerberos V5 [RFC1510]. This encryption type is based on 39 the Triple DES cryptosystem and the HMAC-SHA1 [Krawczyk96] message 40 authentication algorithm. 41 42 The des3-cbc-hmac-sha1 encryption type has been assigned the value 7. 43 The hmac-sha1-des3 checksum type has been assigned the value 12. 44 45 46Encryption Type des3-cbc-hmac-sha1 47 48 EncryptedData using this type must be generated as described in 49 [Horowitz96]. The encryption algorithm is Triple DES in Outer-CBC 50 mode. The keyed hash algorithm is HMAC-SHA1. Unless otherwise 51 specified, a zero IV must be used. If the length of the input data 52 is not a multiple of the block size, zero octets must be used to pad 53 the plaintext to the next eight-octet boundary. The counfounder must 54 be eight random octets (one block). 55 56 57Checksum Type hmac-sha1-des3 58 59 Checksums using this type must be generated as described in 60 [Horowitz96]. The keyed hash algorithm is HMAC-SHA1. 61 62 63 64Horowitz [Page 1] 65 66Internet Draft Kerberos Triple DES with HMAC-SHA1 November, 1996 67 68 69Common Requirements 70 71 Where the Triple DES key is represented as an EncryptionKey, it shall 72 be represented as three DES keys, with parity bits, concatenated 73 together. The key shall be represented with the most significant bit 74 first. 75 76 When keys are generated by the derivation function, a key length of 77 168 bits shall be used. The output bit string will be converted to a 78 valid Triple DES key by inserting DES parity bits after every seventh 79 bit. 80 81 Any implementation which implements either of the encryption or 82 checksum types in this document must support both. 83 84 85Security Considerations 86 87 This entire document defines encryption and checksum types for use 88 with Kerberos V5. 89 90 91References 92 93 [Horowitz96] Horowitz, M., "Key Derivation for Kerberos V5", draft- 94 horowitz-kerb-key-derivation-00.txt, November 1996. 95 [Krawczyk96] Krawczyk, H., Bellare, and M., Canetti, R., "HMAC: 96 Keyed-Hashing for Message Authentication", draft-ietf-ipsec-hmac- 97 md5-01.txt, August, 1996. 98 [RFC1510] Kohl, J. and Neuman, C., "The Kerberos Network 99 Authentication Service (V5)", RFC 1510, September 1993. 100 101 102Author's Address 103 104 Marc Horowitz 105 Cygnus Solutions 106 955 Massachusetts Avenue 107 Cambridge, MA 02139 108 109 Phone: +1 617 354 7688 110 Email: marc@cygnus.com 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126Horowitz [Page 2] 127 128