http://www.rfc-editor.org/rfc/rfc2404.txt
RFC 2404: The Use of HMAC-SHA-1-96 within ESP and AH, C. Madson, R. Glenn1998-11-01T23:00:00-00:00This memo describes the use of the HMAC algorithm in conjunction with the SHA-1 algorithm as an authentication mechanism within the revised IPSEC Encapsulating Security Payload and the revised IPSEC Authentication Header. [STANDARDS-TRACK]