On Mon, Nov 19, 2007 at 03:50:02AM -0500, [EMAIL PROTECTED] wrote: > Title : EAP Generalized Pre-Shared Key (EAP-GPSK) > Filename : draft-ietf-emu-eap-gpsk-07.txt
Minor editorial comments: It looks like the general description of MK derivation in '4. Key Derivation' was not updated to match with the ciphersuite specific changes in 7.1.3 and 7.2.3. The following lines: o inputString = RAND_Peer || ID_Peer || RAND_Server || ID_Server o zero = 0x00 || 0x00 || ... || 0x00 (KS times) o MK = KDF-KS(zero, PL || PSK || CSuite_Sel || inputString)[0..KS-1] would need to be changed to: o inputString = RAND_Peer || ID_Peer || RAND_Server || ID_Server o MK = KDF-KS(PSK[0..KS-1], PL || PSK || CSuite_Sel || inputString)[0..KS-1] 7.1.3 and 7.2.3: MK = GKDF-16 (PSK[0..127], PL || PSK || CSuite_Sel || inputString) MK = GKDF-32 (PSK[0..255], PL || PSK || CSuite_Sel || inputString) The 0..127 and 0..255 are clearly usings bits, but these should be bytes to be consistent with the 0..KS-1 style used elsewhere, i.e., these lines should be MK = GKDF-16 (PSK[0..15], PL || PSK || CSuite_Sel || inputString) MK = GKDF-32 (PSK[0..31], PL || PSK || CSuite_Sel || inputString) Now that definition of 'zero' was removed from MK derivation, Method-ID derivation is using implicitly defined 'zero'. Even though it is relatively obvious what length will be used here, it would be better to state this explicitly: Add following line to 7.1.3 before Method-ID derivation: zero = 0x00 || 0x00 || ... || 0x00 (16 times) Add following line to 7.2.3 before Method-ID derivation: zero = 0x00 || 0x00 || ... || 0x00 (32 times) Especially the ciphersuite 2 case would benefit from explicit statement since HMAC-SHA256 could use any key length. I don't see any particular need for this to be 32 octets, but that would be consistent with other uses of GKDF and anyway, this matches with the KS-octet 'zero' used in Ch. 4. -- Jouni Malinen PGP id EFC895FA _______________________________________________ Emu mailing list [email protected] https://www1.ietf.org/mailman/listinfo/emu
