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Network Working Group                                         B. KaliskiRequest for Comments: 5208                                           EMCCategory: Informational                                         May 2008Public-Key Cryptography Standards (PKCS) #8:Private-Key Information Syntax Specification Version 1.2Status 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 Contents1. Introduction ....................................................22. Definitions .....................................................23. Symbols and Abbreviations .......................................24. General Overview ................................................25. Private-Key Information Syntax ..................................36. Encrypted Private-Key Information Syntax ........................47. Security Considerations .........................................4Appendix A. ASN.1 Syntax ...........................................5   Informative References .............................................6Kaliski                      Informational                      [Page 1]

RFC 5208    PKCS #8: Private-Key Information Syntax Standard    May 20081.  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).Kaliski                      Informational                      [Page 2]

RFC 5208    PKCS #8: Private-Key Information Syntax Standard    May 20085.  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]  IMPLICIT Attributes OPTIONAL }      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.Kaliski                      Informational                      [Page 3]

RFC 5208    PKCS #8: Private-Key Information Syntax Standard    May 20086.  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.Kaliski                      Informational                      [Page 4]

RFC 5208    PKCS #8: Private-Key Information Syntax Standard    May 2008Appendix A.  ASN.1 SyntaxPKCS-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 ToolsDEFINITIONS IMPLICIT TAGS ::=BEGIN-- EXPORTS All ---- All types and values defined in this module is exported for use in-- other ASN.1 modules.IMPORTSinformationFramework         FROM UsefulDefinitions {joint-iso-itu-t(2) ds(5) module(1)                                 usefulDefinitions(0) 3}Attribute         FROM InformationFramework informationFrameworkAlgorithmIdentifier, 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 syntaxPrivateKeyInfo ::= SEQUENCE {   version Version,   privateKeyAlgorithm AlgorithmIdentifier {{PrivateKeyAlgorithms}},   privateKey PrivateKey,   attributes [0] Attributes OPTIONAL }Version ::= INTEGER {v1(0)} (v1,...)PrivateKey ::= OCTET STRINGAttributes ::= SET OF AttributeKaliski                      Informational                      [Page 5]

RFC 5208    PKCS #8: Private-Key Information Syntax Standard    May 2008-- Encrypted private-key information syntaxEncryptedPrivateKeyInfo ::= SEQUENCE {    encryptionAlgorithm AlgorithmIdentifier {{KeyEncryptionAlgorithms}},    encryptedData EncryptedData}EncryptedData ::= OCTET STRINGPrivateKeyAlgorithms ALGORITHM-IDENTIFIER ::= {     ... -- For local profiles}KeyEncryptionAlgorithms ALGORITHM-IDENTIFIER ::= {     ... -- For local profiles}ENDInformative 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.Kaliski                      Informational                      [Page 6]

RFC 5208    PKCS #8: Private-Key Information Syntax Standard    May 2008Author's Addresses   Burt Kaliski   EMC Corporation   176 South Street   Hopkinton, MA  01748   USA   EMail: kaliski_burt@emc.comKaliski                      Informational                      [Page 7]

RFC 5208    PKCS #8: Private-Key Information Syntax Standard    May 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 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.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Kaliski                      Informational                      [Page 8]