5.2. Message Authentication/Integrity - HMAC-SHA1

5.2. Message Authentication/Integrity: HMAC-SHA1

HMAC-SHA1, as defined in Section 4.2.1, SHALL be the default message authentication code. The default session authentication key-length (n_a) SHALL be 160 bits, the default authentication tag length (n_tag) SHALL be 80 bits, and the SRTP_PREFIX_LENGTH SHALL be zero for HMAC-SHA1. In addition, for SRTCP, the pre-defined HMAC-SHA1 MUST NOT be applied with a value of n_tag, nor n_a, that are smaller than these defaults. For SRTP, smaller values are NOT RECOMMENDED, but MAY be used after careful consideration of the issues in Section 7.5 and 9.5.