In support of data integrity, the use of the MD5 [3] message digest algorithm is chosen. A 128-bit digest is calculated over the designated portion of a SNMPv2 message and included as part of the message sent to the recipient.
An appendix of [3] contains a C Programming Language implementation of the algorithm. This code was written with portability being the principal objective. Implementors may wish to optimize the implementation with respect to the characteristics of their hardware and software platforms.
The use of this algorithm in conjunction with the Digest Authentication Protocol (see Section 3) is identified by the ASN.1 object identifier value v2md5AuthProtocol, defined in [4]. (Note that this protocol is a modified version of the md5AuthProtocol protocol defined in RFC 1352.)
For any SNMPv2 party for which the authentication protocol is v2md5AuthProtocol, the size of its private authentication key is 16 octets.
Within an authenticated management communication generated by such a party, the size of the authDigest component of that communication (see Section 3) is 16 octets.