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rfc5208
This is a purely informative rendering of an RFC that includes verified errata. This rendering may not be used as a reference.

The following 'Verified' errata have been incorporated in this document: EID 1890
Network Working Group                                         B. Kaliski
Request for Comments: 5208                                           EMC
Category: Informational                                         May 2008


             Public-Key Cryptography Standards (PKCS) #8:
        Private-Key Information Syntax Specification Version 1.2

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

IESG Note

   The IESG thanks RSA Laboratories for transferring change control to
   the IETF.  Enhancements to this specification that preserve backward
   compatibility are expected in an upcoming IETF standards track
   document.

Abstract

   This document represents a republication of PKCS #8 v1.2 from RSA
   Laboratories' Public Key Cryptography Standard (PKCS) series.  Change
   control is transferred to the IETF.  The body of this document,
   except for the security considerations section, is taken directly
   from the PKCS #8 v1.2 specification.

   This document describes a syntax for private-key information.

Table of Contents

   1. Introduction ....................................................2
   2. Definitions .....................................................2
   3. Symbols and Abbreviations .......................................2
   4. General Overview ................................................2
   5. Private-Key Information Syntax ..................................3
   6. Encrypted Private-Key Information Syntax ........................4
   7. Security Considerations .........................................4
   Appendix A. ASN.1 Syntax ...........................................5
   Informative References .............................................6

1.  Introduction

   This document describes a syntax for private-key information.
   Private-key information includes a private key for some public-key
   algorithm and a set of attributes.  The document also describes a
   syntax for encrypted private keys.  A password-based encryption
   algorithm (e.g., one of those described in [PKCS#5]) could be used to
   encrypt the private-key information.

   The intention of including a set of attributes is to provide a simple
   way for a user to establish trust in information such as a
   distinguished name or a top-level certification authority's public
   key.  While such trust could also be established with a digital
   signature, encryption with a secret key known only to the user is
   just as effective and possibly easier to implement.  A non-exhaustive
   list of attributes is given in [PKCS#9].

2.  Definitions

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

      AlgorithmIdentifier: A type that identifies an algorithm (by
      object identifier) and any associated parameters.  This type is
      defined in [X.509].

      ASN.1: Abstract Syntax Notation One, as defined in [X.208].

      Attribute: A type that contains an attribute type (specified by
      object identifier) and one or more attribute values.  This type is
      defined in [X.501].

      BER: Basic Encoding Rules, as defined in [X.209].

3.  Symbols and Abbreviations

   No symbols or abbreviations are defined in this document.

4.  General Overview

   The next two sections specify private-key information syntax and
   encrypted private-key information syntax.

   This document exports two types: PrivateKeyInfo (Section 6) and
   EncryptedPrivateKeyInfo (Section 7).

5.  Private-Key Information Syntax

   This section gives the syntax for private-key information.

   Private-key information shall have ASN.1 type PrivateKeyInfo:

      PrivateKeyInfo ::= SEQUENCE {
        version                   Version,
        privateKeyAlgorithm       PrivateKeyAlgorithmIdentifier,
        privateKey                PrivateKey,
        attributes           [0]  Attributes OPTIONAL } 

EID 1890 (Verified) is as follows:

Section: 5

Original Text:

attributes           [0]  IMPLICIT Attributes OPTIONAL }

Corrected Text:

attributes           [0]  Attributes OPTIONAL }
Notes:
This change will align the text with the ASN.1 module. Note that the ASN.1 module is an IMPLICIT module and the IMPLICIT tag on this line is unnecessary.
Version ::= INTEGER PrivateKeyAlgorithmIdentifier ::= AlgorithmIdentifier PrivateKey ::= OCTET STRING Attributes ::= SET OF Attribute The fields of type PrivateKeyInfo have the following meanings: version is the syntax version number, for compatibility with future revisions of this document. It shall be 0 for this version of the document. privateKeyAlgorithm identifies the private-key algorithm. One example of a private-key algorithm is PKCS #1's rsaEncryption [PKCS#1]. privateKey is an octet string whose contents are the value of the private key. The interpretation of the contents is defined in the registration of the private-key algorithm. For an RSA private key, for example, the contents are a BER encoding of a value of type RSAPrivateKey. attributes is a set of attributes. These are the extended information that is encrypted along with the private-key information. 6. Encrypted Private-Key Information Syntax This section gives the syntax for encrypted private-key information. Encrypted private-key information shall have ASN.1 type EncryptedPrivateKeyInfo: EncryptedPrivateKeyInfo ::= SEQUENCE { encryptionAlgorithm EncryptionAlgorithmIdentifier, encryptedData EncryptedData } EncryptionAlgorithmIdentifier ::= AlgorithmIdentifier EncryptedData ::= OCTET STRING The fields of type EncryptedPrivateKeyInfo have the following meanings: encryptionAlgorithm identifies the algorithm under which the private-key information is encrypted. Two examples are PKCS #5's pbeWithMD2AndDES-CBC and pbeWithMD5AndDES-CBC [PKCS#5]. encryptedData is the result of encrypting the private-key information. The encryption process involves the following two steps: 1. The private-key information is BER encoded, yielding an octet string. 2. The result of step 1 is encrypted with the secret key to give an octet string, the result of the encryption process. 7. Security Considerations Protection of the private-key information is vital to public-key cryptography. Disclosure of the private-key material to another entity can lead to masquerades. The encryption algorithm used in the encryption process must be as 'strong' as the key it is protecting. Appendix A. ASN.1 Syntax PKCS-8 {iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-8(8) modules(1) pkcs-8(1)} -- $Revision: 1.5 $ -- This module has been checked for conformance with the ASN.1 -- standard by the OSS ASN.1 Tools DEFINITIONS IMPLICIT TAGS ::= BEGIN -- EXPORTS All -- -- All types and values defined in this module is exported for use in -- other ASN.1 modules. IMPORTS informationFramework FROM UsefulDefinitions {joint-iso-itu-t(2) ds(5) module(1) usefulDefinitions(0) 3} Attribute FROM InformationFramework informationFramework AlgorithmIdentifier, ALGORITHM-IDENTIFIER FROM PKCS-5 {iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-5(5) modules(16) pkcs-5(1)}; -- Private-key information syntax PrivateKeyInfo ::= SEQUENCE { version Version, privateKeyAlgorithm AlgorithmIdentifier {{PrivateKeyAlgorithms}}, privateKey PrivateKey, attributes [0] Attributes OPTIONAL } Version ::= INTEGER {v1(0)} (v1,...) PrivateKey ::= OCTET STRING Attributes ::= SET OF Attribute -- Encrypted private-key information syntax EncryptedPrivateKeyInfo ::= SEQUENCE { encryptionAlgorithm AlgorithmIdentifier {{KeyEncryptionAlgorithms}}, encryptedData EncryptedData } EncryptedData ::= OCTET STRING PrivateKeyAlgorithms ALGORITHM-IDENTIFIER ::= { ... -- For local profiles } KeyEncryptionAlgorithms ALGORITHM-IDENTIFIER ::= { ... -- For local profiles } END Informative References [PKCS#1] RSA Laboratories. PKCS #1: RSA Encryption Standard. Version 1.5, November 1993. [PKCS#5] RSA Laboratories. PKCS #5: Password-Based Encryption Standard. Version 1.5, November 1993. [PKCS#9] RSA Laboratories. PKCS #9: Selected Attribute Types. Version 1.1, November 1993. [X.208] CCITT. Recommendation X.208: Specification of Abstract Syntax Notation One (ASN.1). 1988. [X.209] CCITT. Recommendation X.209: Specification of Basic Encoding Rules for Abstract Syntax Notation One (ASN.1). 1988. [X.501] CCITT. Recommendation X.501: The Directory - Models. 1988. [X.509] CCITT. Recommendation X.509: The Directory - Authentication Framework. 1988. Author's Addresses Burt Kaliski EMC Corporation 176 South Street Hopkinton, MA 01748 USA EMail: kaliski_burt@emc.com Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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