MIC

AS2 integrity fingerprint, computed at send and verified via the MDN.

Definition

The MIC is computed over the content after MIME canonicalisation (and, for a signed message, over the content's MIME headers). The receiver recomputes it and returns it in the MDN's Received-Content-MIC field; the sender confirms integrity by comparing the two values. RFC 4130 recommends SHA-1 outbound, with MD5 and SHA-1 accepted inbound.

Origin

Defined in sections 7.1 to 7.3 of RFC 4130 (IETF, 2009); the digest mechanism builds on RFC 1847 (multipart/signed) and S/MIME.

Example in context

MIC = base64( SHA-256( canonicalised-MIME-content ) ) — returned verbatim in the MDN.

Related terms

• Received-Content-MIC — MDN field that carries it.
• NRR — guarantee that rests on MIC matching.