OpenPGP Message Format

Document Type Active Internet-Draft (individual)
Authors Werner Koch  , brian carlson  , Ronald Tse  , Derek Atkins  , Daniel Gillmor 
Last updated 2020-08-31
Replaces draft-koch-openpgp-rfc4880bis
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Network Working Group                                            W. Koch
Internet-Draft                                                GnuPG e.V.
Obsoletes4880, 5581, 6637 (if approved)                       B. Carlson
Intended status: Standards Track                                R.H. Tse
Expires: 4 March 2021                                             Ribose
                                                             D.A. Atkins
                                                            D.K. Gillmor
                                                          31 August 2020

                         OpenPGP Message Format


   { Work in progress to update the OpenPGP specification from RFC4880 }

   This document specifies the message formats used in OpenPGP.  OpenPGP
   provides encryption with public-key or symmetric cryptographic
   algorithms, digital signatures, compression and key management.

   This document is maintained in order to publish all necessary
   information needed to develop interoperable applications based on the
   OpenPGP format.  It is not a step-by-step cookbook for writing an
   application.  It describes only the format and methods needed to
   read, check, generate, and write conforming packets crossing any
   network.  It does not deal with storage and implementation questions.
   It does, however, discuss implementation issues necessary to avoid
   security flaws.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 4 March 2021.

Copyright Notice

   Copyright (c) 2020 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 (
   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
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction
       1.1.  Terms
   2.  General functions
       2.1.  Confidentiality via Encryption
       2.2.  Authentication via Digital Signature
       2.3.  Compression
       2.4.  Conversion to Radix-64
       2.5.  Signature-Only Applications
   3.  Data Element Formats
       3.1.  Scalar Numbers
       3.2.  Multiprecision Integers
       3.3.  Key IDs
       3.4.  Text
       3.5.  Time Fields
       3.6.  Keyrings
       3.7.  String-to-Key (S2K) Specifiers
             3.7.1.  String-to-Key (S2K) Specifier Types
             3.7.2.  String-to-Key Usage
   4.  Packet Syntax
       4.1.  Overview
       4.2.  Packet Headers
             4.2.1.  Old Format Packet Lengths
             4.2.2.  New Format Packet Lengths
             4.2.3.  Packet Length Examples
       4.3.  Packet Tags
   5.  Packet Types
       5.1.  Public-Key Encrypted Session Key Packets (Tag 1)
       5.2.  Signature Packet (Tag 2)
             5.2.1.  Signature Types
             5.2.2.  Version 3 Signature Packet Format
             5.2.3.  Version 4 and 5 Signature Packet Formats
             5.2.4.  Computing Signatures
       5.3.  Symmetric-Key Encrypted Session Key Packets (Tag 3)
       5.4.  One-Pass Signature Packets (Tag 4)
       5.5.  Key Material Packet
             5.5.1.  Key Packet Variants
             5.5.2.  Public-Key Packet Formats
             5.5.3.  Secret-Key Packet Formats
       5.6.  Algorithm-specific Parts of Keys
             5.6.1.  Algorithm-Specific Part for RSA Keys
             5.6.2.  Algorithm-Specific Part for DSA Keys
             5.6.3.  Algorithm-Specific Part for Elgamal Keys
             5.6.4.  Algorithm-Specific Part for ECDSA Keys
             5.6.5.  Algorithm-Specific Part for EdDSA Keys
             5.6.6.  Algorithm-Specific Part for ECDH Keys
       5.7.  Compressed Data Packet (Tag 8)
       5.8.  Symmetrically Encrypted Data Packet (Tag 9)
       5.9.  Marker Packet (Obsolete Literal Packet) (Tag 10)
       5.10.  Literal Data Packet (Tag 11)
       5.11.  Trust Packet (Tag 12)
       5.12.  User ID Packet (Tag 13)
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