RFC 3851 (rfc3851) - Page 2 of 36

Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3

RFC 3851            S/MIME 3.1 Message Specification           July 2004


       3.1.  Preparing the MIME Entity for Signing, Enveloping
             or Compressing . . . . . . . . . . . . . . . . . . . . . 14
       3.2.  The application/pkcs7-mime Type. . . . . . . . . . . . . 19
       3.3.  Creating an Enveloped-only Message . . . . . . . . . . . 21
       3.4.  Creating a Signed-only Message . . . . . . . . . . . . . 22
       3.5.  Creating an Compressed-only Message. . . . . . . . . . . 26
       3.6.  Multiple Operations. . . . . . . . . . . . . . . . . . . 27
       3.7.  Creating a Certificate Management Messagetoc . . . . . . 27
       3.8.  Registration Requests. . . . . . . . . . . . . . . . . . 28
       3.9.  Identifying an S/MIME Message. . . . . . . . . . . . . . 28
   4.  Certificate Processing . . . . . . . . . . . . . . . . . . . . 29
       4.1.  Key Pair Generation. . . . . . . . . . . . . . . . . . . 29
   5.  Security Considerations. . . . . . . . . . . . . . . . . . . . 29
   A.  ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . . . . 31
   B.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
       B.1.  Normative References . . . . . . . . . . . . . . . . . . 32
       B.2.  Informative References . . . . . . . . . . . . . . . . . 34
   C.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 35
   D.  Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 35
       Full Copyright Statement . . . . . . . . . . . . . . . . . . . 36

1.  Introduction

   S/MIME (Secure/Multipurpose Internet Mail Extensions) provides a
   consistent way to send and receive secure MIME data.  Based on the
   popular Internet MIME standard, S/MIME provides the following
   cryptographic security services for electronic messaging
   applications:  authentication, message integrity and non-repudiation
   of origin (using digital signatures), and data confidentiality (using
   encryption).

   S/MIME can be used by traditional mail user agents (MUAs) to add
   cryptographic security services to mail that is sent, and to
   interpret cryptographic security services in mail that is received.
   However, S/MIME is not restricted to mail; it can be used with any
   transport mechanism that transports MIME data, such as HTTP.  As
   such, S/MIME takes advantage of the object-based features of MIME and
   allows secure messages to be exchanged in mixed-transport systems.

   Further, S/MIME can be used in automated message transfer agents that
   use cryptographic security services that do not require any human
   intervention, such as the signing of software-generated documents and
   the encryption of FAX messages sent over the Internet.








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