Network Working Group Burt Kaliski, EMC
Internet Draft April 16, 2008
Intended Status: Informational
Expires: October 16, 2008
PKCS #8: Private-Key Information Syntax Standard
Version 1.2
draft-kaliski-pkcs8-00.txt
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Copyright (C) The IETF Trust (2008).
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.
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Table of Contents
1. Introduction...................................................2
2. References.....................................................2
3. Definitions....................................................3
4. Symbols and Abbreviations......................................3
5. General Overview...............................................3
6. Private Key Information Syntax.................................3
7. Encrypted private-key information syntax.......................4
8. IANA Considerations............................................5
1. Introduction
This standard 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 standard 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. 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.
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X.509 CCITT. Recommendation X.509: The Directory - Authentication
Framework. 1988.
3. Definitions
For the purposes of this standard, 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.
4. Symbols and Abbreviations
No symbols or abbreviations are defined in this standard.
5. General Overview
The next two sections specify private-key information syntax and
encrypted private-key information syntax.
This standard exports two types: PrivateKeyInfo (Section 6) and
EncryptedPrivateKeyInfo (Section 7).
6. 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
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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 standard. It shall be 0 for this version
of the standard.
privateKeyAlgorithm identifies the private-key algorithm. One
example of a private-key algorithm is PKCS #1's rsaEncryption.
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.
7. 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.
encryptedData is the result of encrypting the private-key
information.
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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.
8. 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.
9. IANA Considerations
None. Please remove this section prior to publication as an RFC.
Revision History
Version 1.0
Version 1.0 was distributed to participants in RSA Data Security,
Inc.'s Public-Key Cryptography Standards meetings in February and
March 1991.
Version 1.1
Version 1.1 is part of the June 3, 1991 initial public release of
PKCS. Version 1.1 was published as NIST/OSI Implementors'
Workshop document SEC-SIG-91-23.
Version 1.2
Version 1.2 incorporates several editorial changes, including
updates to the references and the addition of a revision history.
Author's Addresses
Burt Kaliski
174 Middlesex Turnpike
Bedford, MA 01730
kaliski_burt@emc.com
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