hmac_md5.nx

hmac_md5.nx -- HMAC with MD5 (RFC 2104). Like HMAC-SHA1: even though plain MD5 is broken for signatures, HMAC-MD5 remains safe for authentication because HMAC relies on pseudo-randomness of the keyed mix, not collision resistance. Still on the wire in: - RADIUS Access-Request Message-Authenticator (RFC 3579) - CRAM-MD5 SASL auth (IMAP, POP3, SMTP legacy) - Microsoft MS-CHAP-v2 password challenge - NTLMv1 / NTLMv2 (the real world's Windows auth) Composes md5.nx with standard ipad/opad construction. Invariants: HM1 Output = 16 bytes (MD5 tag length). HM2 Matches RFC 2104 Appendix test vectors.