Network Working Group M. Nystrom

Network Working Group M. Nystrom
Request for Comments: 2986 B. Kaliski
Obsoletes: 2314 RSA Security
Category: Informational November 2000

PKCS #10: Certification Request Syntax Specification
Version 1.7

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.

Copyright Notice

Copyright (C) The Internet Society (2000). All Rights Reserved.

Abstract

This memo represents a republication of PKCS #10 v1.7 from RSA
Laboratories' Public-Key Cryptography Standards (PKCS) series, and
change control is retained within the PKCS process. The body of this
document, except for the security considerations section, is taken
directly from the PKCS #9 v2.0 or the PKCS #10 v1.7 document.

This memo describes a syntax for certification requests.

Table of Contents

1. Introduction ................................................. 2
2. Definitions and notation ..................................... 2
2.1 Definitions ................................................. 2
2.2 Notation .................................................... 4
3. Overview ..................................................... 4
4. Certification request syntax ................................. 5
4.1 CertificationRequestInfo .................................... 5
4.2 CertificationRequest ........................................ 7
5. Security Considerations ...................................... 8
6. Authors' Addresses ........................................... 8
A. ASN.1 module ................................................. 9
B. Intellectual property considerations ........................ 10
C. Revision history ............................................ 10
D. References .................................................. 11
E. Contact information & About PKCS ............................ 12
Full Copyright Statement ........................................ 14

Nystrom & Kaliski Informational [Page 1]

RFC 2986 Certification Request Syntax Specification November 2000

1. Introduction

This document describes syntax for certification requests. A
certification request consists of a distinguished name, a public key,
and optionally a set of attributes, collectively signed by the entity
requesting certification. Certification requests are sent to a
certification authority, which transforms the request into an X.509
[9] public-key certificate. (In what form the certification
authority returns the newly signed certificate is outside the scope
of this document. A PKCS #7 [2] message is one possibility.)

The intention of including a set of attributes is twofold: to provide
other information about a given entity , or a "challenge password" by
which the entity may later request certificate revocation; and to
provide attributes for inclusion in X.509 certificates. A non-
exhaustive list of attributes is given in PKCS #9 [3].

Certification authorities may also require non-electronic forms of
request and may return non-electronic replies. It is expected that
descriptions of such forms, which are outside the scope of this
document, will be available from certification authorities.

The preliminary intended application of this document is to support
PKCS #7 cryptographic messages, but it is expected that other
applications will be developed (see e.g. [4]).

2. Definitions and notation

2.1 Definitions

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

ALGORITHM An information object class defined in X.509 to
describe objects composed of an algorithm (a unique
object identifier) and its parameters (any ASN.1
type). The values of objects in this class can be
represented by the ASN.1 type AlgorithmIdentifier{}.
ALGORITHM is defined as the "useful" information
object class TYPE-IDENTIFIER, specified in [11],
Annex A.

AlgorithmIdentifier{}
A useful parameterized version of X.509 type
AlgorithmIdentifier is defined in this document.
This type tightly binds pairs of algorithm object
identifiers to their associated parameter types.
When referenced, the single parameter of
AlgorithmIdentifier{} specifies a constraint on the

Nystrom & Kaliski Informational [Page 2]

RFC 2986 Certification Request Syntax Specification November 2000

pairs of values that may appear in that instance of
the type. The encoded values of
AlgorithmIdentifier{} are equivalent to those of type
AlgorithmIdentifier.

ASN.1 Abstract Syntax Notation One, as defined in the ASN.1
standards ([10], [11], [12], and [13]).

ATTRIBUTE This class describes objects composed of an attribute
(a unique object identifier) and an associated set of
attribute values (any ASN.1 type). The values of
objects in this class can be represented by type
Attribute{}.

Attribute{} A useful parameterized version of X.501 [8] type
Attribute is defined in this document. This type
tightly binds pairs of attribute type object
identifiers to one or more attribute values types.
In the ASN.1 open type notation, an attribute type is
defined as ATTRIBUTE.&id and an attribute value as
ATTRIBUTE.&Type. When referenced, the single
parameter of Attribute{} specifies a constraint on
the pairs of values that may appear in an instance of
the type. The encoded values of Attribute{} are
equivalent to those of type Attribute.

BER Basic Encoding Rules for ASN.1, as defined in X.690
([14]).

Certificate A type that binds a subject entity's distinguished
name to a public key with a digital signature. This
type is defined in X.509. This type also contains
the distinguished name of the certificate issuer (the
signer), an issuer-specific serial number, the
issuer's signature algorithm identifier, a validity
period, and an optional set of certificate
extensions.

DER Distinguished Encoding Rules for ASN.1, as defined in
X.690. DER is a subset of BER.

Name A type that uniquely identifies or "distinguishes"
objects in an X.500 [7] directory. This type is
defined in X.501. In an X.509 certificate, the type
identifies the certificate issuer and the certificate
subject, the entity whose public key is certified.

Nystrom & Kaliski Informational [Page 3]

RFC 2986 Certification Request Syntax Specification November 2000

2.2 Notation

No special notation is used in this document.

3. Overview

A certification request consists of three parts: "certification
request information," a signature algorithm identifier, and a digital
signature on the certification request information. The
certification request information consists of the entity's
distinguished name, the entity's public key, and a set of attributes
providing other information about the entity.

The process by which a certification request is constructed involves
the following steps:

1. A CertificationRequestInfo value containing a subject
distinguished name, a subject public key, and optionally a
set of attributes is constructed by an entity requesting
certification.

2. The CertificationRequestInfo value is signed with the subject
entity's private key. (See Section 4.2.)

3. The CertificationRequestInfo value, a signature algorithm
identifier, and the entity's signature are collected together
into a CertificationRequest value, defined below.

A certification authority fulfills the request by authenticating the
requesting entity and verifying the entity's signature, and, if the
request is valid, constructing an X.509 certificate from the
distinguished name and public key, the issuer name, and the
certification authority's choice of serial number, validity period,
and signature algorithm. If the certification request contains any
PKCS #9 attributes, the certification authority may also use the
values in these attributes as well as other information known to the
certification authority to construct X.509 certificate extensions.

In what form the certification authority returns the new certificate
is outside the scope of this document. One possibility is a PKCS #7
cryptographic message with content type signedData, following the
degenerate case where there are no signers. The return message may
include a certification path from the new certificate to the
certification authority. It may also include other certificates such
as cross-certificates that the certification authority considers
helpful, and it may include certificate-revocation lists (CRLs).
Another possibility is that the certification authority inserts the
new certificate into a central database.

Nystrom & Kaliski Informational [Page 4]

RFC 2986 Certification Request Syntax Specification November 2000

Note 1 - An entity would typically send a certification request after
generating a public-key/private-key pair, but may also do so after a
change in the entity's distinguished name.

Note 2 - The signature on the certification request prevents an
entity from requesting a certificate with another party's public key.
Such an attack would give the entity the minor ability to pretend to
be the originator of any message signed by the other party. This
attack is significant only if the entity does not know the message
being signed and the signed part of the message does not identify the
signer. The entity would still not be able to decrypt messages
intended for the other party, of course.

Note 3 - How the entity sends the certification request to a
certification authority is outside the scope of this document. Both
paper and electronic forms are possible.

Note 4 - This document is not compatible with the certification
request syntax for Privacy-Enhanced Mail, as described in RFC 1424
[5]. The syntax here differs in three respects: It allows a set of
attributes; it does not include issuer name, serial number, or
validity period; and it does not require an "innocuous" message to be
signed. This document is designed to minimize request size, an
important feature for certification authorities accepting requests on
paper.

4. Certification request syntax

This section is divided into two parts. The first part describes the
certification-request-information type CertificationRequestInfo, and
the second part describes the top-level type CertificationRequest.

4.1 CertificationRequestInfo

Certification request information shall have ASN.1 type
CertificationRequestInfo:

CertificationRequestInfo ::= SEQUENCE {
version INTEGER { v1(0) } (v1,...),
subject Name,
subjectPKInfo SubjectPublicKeyInfo{{ PKInfoAlgorithms }},
attributes [0] Attributes{{ CRIAttributes }}
}

SubjectPublicKeyInfo { ALGORITHM : IOSet} ::= SEQUENCE {
algorithm AlgorithmIdentifier {{IOSet}},
subjectPublicKey BIT STRING
}

Nystrom & Kaliski Informational [Page 5]

RFC 2986 Certification Request Syntax Specification November 2000

PKInfoAlgorithms ALGORITHM ::= {
... -- add any locally defined algorithms here -- }

Attributes { ATTRIBUTE:IOSet } ::= SET OF Attribute{{ IOSet }}

CRIAttributes ATTRIBUTE ::= {
... -- add any locally defined attributes here -- }

Attribute { ATTRIBUTE:IOSet } ::= SEQUENCE {
type ATTRIBUTE.&id({IOSet}),
values SET SIZE(1..MAX) OF ATTRIBUTE.&Type({IOSet}{@type})
}

The components of type CertificationRequestInfo have the following
meanings:

version is the version number, for compatibility with future
revisions of this document. It shall be 0 for this version of
the standard.

subject is the distinguished name of the certificate subject
(the entity whose public key is to be certified).

subjectPublicKeyInfo contains information about the public key
being certified. The information identifies the entity's
public-key algorithm (and any associated parameters); examples
of public-key algorithms include the rsaEncryption object
identifier from PKCS #1 [1]. The information also includes a
bit-string representation of the entity's public key. For the
public-key algorithm just mentioned, the bit string contains
the DER encoding of a value of PKCS #1 type RSAPublicKey. The
values of type SubjectPublicKeyInfo{} allowed for
subjectPKInfo are constrained to the values specified by the
information object set PKInfoAlgorithms, which includes the
extension marker (...). Definitions of specific algorithm
objects are left to specifications that reference this
document. Such specifications will be interoperable with
their future versions if any additional algorithm objects are
added after the extension marker.

attributes is a collection of attributes providing additional
information about the subject of the certificate. Some
attribute types that might be useful here are defined in PKCS
#9. An example is the challenge-password attribute, which
specifies a password by which the entity may request
certificate revocation. Another example is information to
appear in X.509 certificate extensions (e.g. the
extensionRequest attribute from PKCS #9). The values of type

Nystrom & Kaliski Informational [Page 6]

RFC 2986 Certification Request Syntax Specification November 2000

Attributes{} allowed for attributes are constrained to the
values specified by the information object set CRIAttributes.
Definitions of specific attribute objects are left to
specifications that reference this document. Such
specifications will be interoperable with their future
versions if any additional attribute objects are added after
the extension marker.

4.2 CertificationRequest

A certification request shall have ASN.1 type CertificationRequest:

CertificationRequest ::= SEQUENCE {
certificationRequestInfo CertificationRequestInfo,
signatureAlgorithm AlgorithmIdentifier{{ SignatureAlgorithms }},
signature BIT STRING
}

AlgorithmIdentifier {ALGORITHM:IOSet } ::= SEQUENCE {
algorithm ALGORITHM.&id({IOSet}),
parameters ALGORITHM.&Type({IOSet}{@algorithm}) OPTIONAL
}

SignatureAlgorithms ALGORITHM ::= {
... -- add any locally defined algorithms here -- }

The components of type CertificationRequest have the following
meanings:

certificateRequestInfo is the "certification request
information." It is the value being signed.

signatureAlgorithm identifies the signature algorithm (and any
associated parameters) under which the certification-request
information is signed. For example, a specification might
include an ALGORITHM object for PKCS #1's
md5WithRSAEncryption in the information object set
SignatureAlgorithms:

SignatureAlgorithms ALGORITHM ::= {
...,
{ NULL IDENTIFIED BY md5WithRSAEncryption }
}

signature is the result of signing the certification request
information with the certification request subject's private
key.

Nystrom & Kaliski Informational [Page 7]

RFC 2986 Certification Request Syntax Specification November 2000

The signature process consists of two steps:

1. The value of the certificationRequestInfo component is DER
encoded, yielding an octet string.

2. The result of step 1 is signed with the certification request
subject's private key under the specified signature
algorithm, yielding a bit string, the signature.

Note - An equivalent syntax for CertificationRequest could be
written:

CertificationRequest ::= SIGNED { EncodedCertificationRequestInfo }
(CONSTRAINED BY { -- Verify or sign encoded
-- CertificationRequestInfo -- })

EncodedCertificationRequestInfo ::=
TYPE-IDENTIFIER.&Type(CertificationRequestInfo)

SIGNED { ToBeSigned } ::= SEQUENCE {
toBeSigned ToBeSigned,
algorithm AlgorithmIdentifier { {SignatureAlgorithms} },
signature BIT STRING
}

5. Security Considerations

Security issues are discussed throughout this memo.

6. Authors' Addresses

Magnus Nystrom
RSA Security
Box 10704
S-121 29 Stockholm
Sweden

EMail: [email protected]

Burt Kaliski
RSA Security
20 Crosby Drive
Bedford, MA 01730 USA

EMail: [email protected]

Nystrom & Kaliski Informational [Page 8]

RFC 2986 Certification Request Syntax Specification November 2000

APPENDICES

A. ASN.1 Module

This appendix includes all of the ASN.1 type and value definitions
contained in this document in the form of the ASN.1 module PKCS-10.

PKCS-10 {iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-10(10) modules(1) pkcs-10(1)}

DEFINITIONS IMPLICIT TAGS ::=

BEGIN

-- EXPORTS All --

-- All types and values defined in this module are exported for use
-- in other ASN.1 modules.

IMPORTS

informationFramework, authenticationFramework
FROM UsefulDefinitions {joint-iso-itu-t(2) ds(5) module(1)
usefulDefinitions(0) 3}

ATTRIBUTE, Name
FROM InformationFramework informationFramework

ALGORITHM
FROM AuthenticationFramework authenticationFramework;

-- Certificate requests
CertificationRequestInfo ::= SEQUENCE {
version INTEGER { v1(0) } (v1,...),
subject Name,
subjectPKInfo SubjectPublicKeyInfo{{ PKInfoAlgorithms }},
attributes [0] Attributes{{ CRIAttributes }}
}

SubjectPublicKeyInfo {ALGORITHM: IOSet} ::= SEQUENCE {
algorithm AlgorithmIdentifier {{IOSet}},
subjectPublicKey BIT STRING
}

PKInfoAlgorithms ALGORITHM ::= {
... -- add any locally defined algorithms here -- }

Attributes { ATTRIBUTE:IOSet } ::= SET OF Attribute{{ IOSet }}

Nystrom & Kaliski Informational [Page 9]

RFC 2986 Certification Request Syntax Specification November 2000

CRIAttributes ATTRIBUTE ::= {
... -- add any locally defined attributes here -- }

Attribute { ATTRIBUTE:IOSet } ::= SEQUENCE {
type ATTRIBUTE.&id({IOSet}),
values SET SIZE(1..MAX) OF ATTRIBUTE.&Type({IOSet}{@type})
}

CertificationRequest ::= SEQUENCE {
certificationRequestInfo CertificationRequestInfo,
signatureAlgorithm AlgorithmIdentifier{{ SignatureAlgorithms }},
signature BIT STRING
}

AlgorithmIdentifier {ALGORITHM:IOSet } ::= SEQUENCE {
algorithm ALGORITHM.&id({IOSet}),
parameters ALGORITHM.&Type({IOSet}{@algorithm}) OPTIONAL
}

SignatureAlgorithms ALGORITHM ::= {
... -- add any locally defined algorithms here -- }

END

B. Intellectual property considerations

RSA Security makes no patent claims on the general constructions
described in this document, although specific underlying techniques
may be covered.

License to copy this document is granted provided that it is
identified as "RSA Security Inc. Public-Key Cryptography Standards
(PKCS)" in all material mentioning or referencing this document.

RSA Security makes no representations regarding intellectual property
claims by other parties. Such determination is the responsibility of
the user.

C. Revision history

Version 1.0

Version 1.0 was the previous version of this document (also
published as "version 1.5" in [6]).

Nystrom & Kaliski Informational [Page 10]

RFC 2986 Certification Request Syntax Specification November 2000

Version 1.7

This version incorporates several editorial changes, including
updates to the references, and changes to ASN.1 type
definitions. The following substantive changes have been made:

- This version refers to X.680-X.690, the current international
standards for ASN.1 and its encoding rules. All references
to X.208 and X.209 have been eliminated.

- The X.690 standard requires that the encoded values of SET OF
components be sorted in ascending order under DER.
Regardless of this, applications should not rely on the
ordering of attribute components.

- All references to PKCS #6 Extended-Certificate Syntax
Standard have been removed. With the addition of extensions
to X.509 version 3 certificates, RSA Laboratories is
withdrawing support for PKCS #6.

Note - The reason for using version 1.7 for this document is to avoid
confusion with [6], which is named version 1.5, and an unsupported
PKCS #10 version named Version 1.6.

D. References

[1] RSA Laboratories. PKCS #1: RSA Encryption Standard. Version 2.0,
October 1998.

[2] RSA Laboratories. PKCS #7: Cryptographic Message Syntax
Standard. Version 1.5, November 1993.

[3] RSA Laboratories. PKCS #9: Selected Attribute Types. Version
2.0, February 2000.

[4] Adams, C. and S. Farrell, "Internet X.509 Public Key
Infrastructure - Certificate Management Protocols", RFC 2510,
March 1999.

[5] Kaliski, B., "Privacy Enhancement for Internet Electronic Mail:
Part IV: Key Certification and Related Services", RFC 1424,
February 1993.

[6] Kaliski, B., "PKCS #10: Certification Request Syntax Version
1.5", RFC 2314, March 1998.

Nystrom & Kaliski Informational [Page 11]

RFC 2986 Certification Request Syntax Specification November 2000

[7] ITU-T Recommendation X.500 (1997) | ISO/IEC 9594-1:1998,
Information technology - Open Systems Interconnection - The
Directory: Overview of concepts, models and services.

[8] ITU-T Recommendation X.501 (1993) | ISO/IEC 9594-2:1995,
Information technology - Open Systems Interconnection - The
Directory: Models.

[9] ITU-T Recommendation X.509 (1997) | ISO/IEC 9594-8:1998,
Information technology - Open Systems Interconnection -The
Directory: Authentication framework.

[10] ITU-T Recommendation X.680 (1997) | ISO/IEC 8824-1:1998,
Information Technology - Abstract Syntax Notation One (ASN.1):
Specification of Basic Notation.

[11] ITU-T Recommendation X.681 (1997) | ISO/IEC 8824-2:1998,
Information Technology - Abstract Syntax Notation One (ASN.1):
Information Object Specification.

[12] ITU-T Recommendation X.682 (1997) | ISO/IEC 8824-3:1998,
Information Technology - Abstract Syntax Notation One (ASN.1):
Constraint Specification.

[13] ITU-T Recommendation X.683 (1997) | ISO/IEC 8824-4:1998,
Information Technology - Abstract Syntax Notation One (ASN.1):
Parameterization of ASN.1 Specifications.

[14] ITU-T Recommendation X.690 (1997) | ISO/IEC 8825-1:1998,
Information Technology - ASN.1 Encoding Rules: Specification of
Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER).

E. Contact Information & About PKCS

The Public-Key Cryptography Standards are specifications produced by
RSA Laboratories in cooperation with secure systems developers
worldwide for the purpose of accelerating the deployment of public-
key cryptography. First published in 1991 as a result of meetings
with a small group of early adopters of public-key technology, the
PKCS documents have become widely referenced and implemented.
Contributions from the PKCS series have become part of many formal
and de facto standards, including ANSI X9 documents, PKIX, SET,
S/MIME, and SSL.

Nystrom & Kaliski Informational [Page 12]

RFC 2986 Certification Request Syntax Specification November 2000

Further development of PKCS occurs through mailing list discussions
and occasional workshops, and suggestions for improvement are
welcome. For more information, contact:

PKCS Editor
RSA Laboratories
20 Crosby Drive
Bedford, MA 01730 USA
[email protected]
http://www.rsasecurity.com/rsalabs/pkcs

Nystrom & Kaliski Informational [Page 13]

RFC 2986 Certification Request Syntax Specification November 2000

Full Copyright Statement

Copyright (C) The Internet Society 2000. All Rights Reserved.

This document and translations of it may be copied and furnished to
others provided that the above copyright notice and this paragraph
are included on all such copies. However, this document itself may
not be modified in any way, such as by removing the copyright notice
or references to the Internet Society or other Internet
organizations, except as required to translate it into languages
other than English.

The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS 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.

Acknowledgement

Funding for the RFC Editor function is currently provided by the
Internet Society.

Nystrom & Kaliski Informational [Page 14]