RFC 3855 (rfc3855) - Page 2 of 12

Transporting Secure/Multipurpose Internet Mail Extensions (S/MIME) Objects in X

RFC 3855          Transporting S/MIME Objects in X.400         July 2004


1.1.  Terminology

   The key words "MUST", "SHALL", "REQUIRED", "SHOULD", "RECOMMENDED",
   and "MAY" in this document are to be interpreted as described in BCP
   14, RFC 2119 [MUSTSHOULD].

1.2.  Definitions

   For the purposes of this document, the following definitions apply.

   ASN.1: Abstract Syntax Notation One, as defined in ISO/IEC 8824.

   Object Identifier (OID): A globally unique identifier value
   consisting of a sequence of integer values assigned through
   distributed registration as specified by ISO/IEC 8824.

   Transfer Encoding: A reversible transformation made on data so 8-bit
   or binary data may be sent via a channel that only transmits 7-bit
   data.

1.3.  Compatibility with Existing S/MIME Implementations

   It is a goal of this document to, if possible, maintain backward
   compatibility with existing X.400 implementations that employ S/MIME
   v3.1 wrappers.

2.  S/MIME Packaging

2.1.  The X.400 Message Structure

   This section reviews the X.400 message format.  An X.400 message has
   two parts, the envelope and the content, as described in X.402
   [X.400]:

   Envelope --  An information object whose composition varies from one
      transmittal step to another and that variously identifies the
      message's originator and potential recipients, documents its
      previous conveyance and directs its subsequent conveyance by the
      Message Transfer System (MTS), and characterizes its content.

   Content -- The content is the piece of information that the
      originating User Agent wants to be delivered to one or more
      recipients.  The MTS neither examines nor modifies the content,
      except for conversion, during its conveyance of the message.  MTS
      conversion is not applicable to the scenario of this document
      because such conversion is incompatible with CMS protection
      mechanisms.




Hoffman & Bonatti           Standards Track