multipart/signed
MIME framing for signed messages, the basis of AS2 and detached-signature S/MIME.
Definition
multipart/signed wraps two parts: the first is the protected content (left in the clear and readable), the second is the signature, typed application/pkcs7-signature in S/MIME. The protocol parameter names the signature format and micalg names the hash algorithm. This is the structure AS2 uses to sign an exchange without encrypting the body.
Origin
Defined in RFC 1847 (Security Multiparts for MIME, IETF, 1995), reused by RFC 8551 (S/MIME 4.0) and RFC 4130 (AS2).
Example in context
Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="----=_Part_42"