RFC 1847 (rfc1847) - Page 3 of 11

Security Multiparts for MIME: Multipart/Signed and Multipart/Encrypted

RFC 1847                  Security Multiparts               October 1995


2.1.  Definition of Multipart/Signed

   (1)  MIME type name: multipart

   (2)  MIME subtype name: signed

   (3)  Required parameters: boundary, protocol, and micalg

   (4)  Optional parameters: none

   (5)  Security considerations: Must be treated as opaque while in
        transit

   The multipart/signed content type contains exactly two body parts.
   The first body part is the body part over which the digital signature
   was created, including its MIME headers.  The second body part
   contains the control information necessary to verify the digital
   signature.  The first body part may contain any valid MIME content
   type, labeled accordingly.  The second body part is labeled according
   to the value of the protocol parameter.

   The attribute token for the protocol parameter is "protocol", i.e.,

    parameter := "protocol" "=" value

   The value token is comprised of the type and sub-type tokens of the
   Content-Type: header of the second body part, i.e.,

    value :=  type "/" subtype 

   where the type and subtype tokens are defined by the MIME [2]
   specification.  The semantics of the protocol parameter are defined
   according to its value.

   The attribute token for the micalg parameter is "micalg", i.e.,

    parameter := "micalg" "=" value

   The Message Integrity Check (MIC) is the name given to the quantity
   computed over the body part with a message digest or hash function,
   in support of the digital signature service.  Valid value tokens are
   defined by the specification for the value of the protocol parameter.
   The value may be a comma (",") separated list of tokens, indicating
   the use of multiple MIC algorithms.  As a result, the comma (",")
   character is explicitly excluded from the list of characters that may
   be included in a token used as a value of the micalg parameter.  If
   multiple MIC algorithms are specified, the purpose and use of the
   multiple algorithms is defined by the protocol.  If the MIC algorithm



Galvin, et al               Standards Track