Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Message Specification
RFC 8551

Document Type RFC - Proposed Standard (April 2019; No errata)
Obsoletes RFC 5751
Last updated 2019-04-30
Replaces draft-schaad-rfc5751-bis
Stream IETF
Formats plain text pdf htmlized bibtex
Reviews
Stream WG state Submitted to IESG for Publication
Document shepherd Russ Housley
Shepherd write-up Show (last changed 2017-04-14)
IESG IESG state RFC 8551 (Proposed Standard)
Consensus Boilerplate Yes
Telechat date
Responsible AD Eric Rescorla
Send notices to Russ Housley <housley@vigilsec.com>
IANA IANA review state Version Changed - Review Needed
IANA action state RFC-Ed-Ack
Internet Engineering Task Force (IETF)                         J. Schaad
Request for Comments: 8551                                August Cellars
Obsoletes: 5751                                              B. Ramsdell
Category: Standards Track                         Brute Squad Labs, Inc.
ISSN: 2070-1721                                                S. Turner
                                                                   sn3rd
                                                              April 2019

   Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
                         Message Specification

Abstract

   This document defines Secure/Multipurpose Internet Mail Extensions
   (S/MIME) version 4.0.  S/MIME provides a consistent way to send and
   receive secure MIME data.  Digital signatures provide authentication,
   message integrity, and non-repudiation with proof of origin.
   Encryption provides data confidentiality.  Compression can be used to
   reduce data size.  This document obsoletes RFC 5751.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8551.

Schaad, et al.               Standards Track                    [Page 1]
RFC 8551            S/MIME 4.0 Message Specification          April 2019

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Schaad, et al.               Standards Track                    [Page 2]
RFC 8551            S/MIME 4.0 Message Specification          April 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.1.  Specification Overview  . . . . . . . . . . . . . . . . .   5
     1.2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   6
     1.3.  Conventions Used in This Document . . . . . . . . . . . .   7
     1.4.  Compatibility with Prior Practice of S/MIME . . . . . . .   8
     1.5.  Changes from S/MIME v3 to S/MIME v3.1 . . . . . . . . . .   9
     1.6.  Changes from S/MIME v3.1 to S/MIME v3.2 . . . . . . . . .   9
     1.7.  Changes for S/MIME v4.0 . . . . . . . . . . . . . . . . .  11
   2.  CMS Options . . . . . . . . . . . . . . . . . . . . . . . . .  12
     2.1.  DigestAlgorithmIdentifier . . . . . . . . . . . . . . . .  12
     2.2.  SignatureAlgorithmIdentifier  . . . . . . . . . . . . . .  12
     2.3.  KeyEncryptionAlgorithmIdentifier  . . . . . . . . . . . .  13
     2.4.  General Syntax  . . . . . . . . . . . . . . . . . . . . .  13
       2.4.1.  Data Content Type . . . . . . . . . . . . . . . . . .  14
       2.4.2.  SignedData Content Type . . . . . . . . . . . . . . .  14
       2.4.3.  EnvelopedData Content Type  . . . . . . . . . . . . .  14
       2.4.4.  AuthEnvelopedData Content Type  . . . . . . . . . . .  14
       2.4.5.  CompressedData Content Type . . . . . . . . . . . . .  14
     2.5.  Attributes and the SignerInfo Type  . . . . . . . . . . .  15
       2.5.1.  Signing Time Attribute  . . . . . . . . . . . . . . .  15
       2.5.2.  SMIMECapabilities Attribute . . . . . . . . . . . . .  16
       2.5.3.  Encryption Key Preference Attribute . . . . . . . . .  17
Show full document text