Network Working Group                                       B. Kaliski
Request for Comments: 2314                       RSA Laboratories East
Category: Informational                                     March 1998


                PKCS #10: Certification Request Syntax
                             Version 1.5

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 (1998).  All Rights Reserved.

Overview

  This document describes a syntax for certification requests.

1. Scope

  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, who transforms the request to an X.509
  public-key certificate, or a PKCS #6 extended certificate. (In what
  form the certification authority returns the newly signed certificate
  is outside the scope of this document. A PKCS #7 message is one
  possibility.)

  The intention of including a set of attributes is twofold: to provide
  other information about a given entity, such as the postal address to
  which the signed certificate should be returned if electronic mail is
  not available, or a "challenge password" by which the entity may
  later request certificate revocation; and to provide attributes for a
  PKCS #6 extended certificate. A non-exhaustive list of attributes is
  given in PKCS #9.

  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 the certification authority.






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  The preliminary intended application of this document is to support
  PKCS #7 cryptographic messages, but is expected that other
  applications will be developed.

2. References

  PKCS #1   RSA Laboratories. PKCS #1: RSA Encryption
            Standard. Version 1.5, November 1993.

  PKCS #6   RSA Laboratories. PKCS #6: Extended-Certificate
            Syntax. Version 1.5, November 1993.

  PKCS #7   RSA Laboratories. PKCS #7: Cryptographic Message
            Syntax. Version 1.5, November 1993.

  PKCS #9   RSA Laboratories. PKCS #9: Selected Attribute
            Types. Version 1.1, November 1993.

  RFC 1424  Kaliski, B., "Privacy Enhancement for
            Internet Electronic Mail: Part IV: Key
            Certification and Related Services," RFC 1424,
            February 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.500     CCITT. Recommendation X.500: The Directory--
            Overview of Concepts, Models and
            Services. 1988.

  X.501     CCITT. Recommendation X.501: The Directory--
            Models. 1988.

  X.509     CCITT. Recommendation X.509: The Directory--
            Authentication Framework. 1988.

3. 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.




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  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.

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

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

  Certificate: A type that binds an 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, and a validity period.

  DER: Distinguished Encoding Rules for ASN.1, as defined in X.509,
  Section 8.7.

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

4. Symbols and abbreviations

  No symbols or abbreviations are defined in this document.

5. General overview

  The next section specifies certification request syntax.

  This document exports one type, CertificationRequest.

6. Certification request syntax

  This section gives the syntax for certification requests.

  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.









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

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

       2.   The CertificationRequestInfo value is signed with
            the entity's private key. (See Section 6.2.)

       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 verifying the
  entity's signature, and, if it is valid, constructing a X.509
  certificate from the distinguished name and public key, as well as an
  issuer name, serial number, validity period, and signature algorithm
  of the certification authority's choice. If the certification request
  contains a PKCS #9 extended-certificate-attributes attribute, the
  certification authority also constructs a PKCS #6 extended
  certificate from the X.509 certificate and the extended-certificate-
  attributes attribute value.

  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.

  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.

  Notes.

       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.





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       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.

       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.

       4.   This document is not compatible with the
            certification request syntax for Privacy-Enhanced Mail, as
            described in RFC 1424. The syntax in this document 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. The syntax in this document is designed to minimize
            request size, an important constraint for those
            certification authorities accepting requests on paper.

6.1 CertificationRequestInfo

  Certification request information shall have ASN.1 type
  CertificationRequestInfo:

  CertificationRequestInfo ::= SEQUENCE {
    version Version,
    subject Name,
    subjectPublicKeyInfo SubjectPublicKeyInfo,
    attributes [0] IMPLICIT Attributes }

  Version ::= INTEGER

  Attributes ::= SET OF Attribute

  The fields of type CertificationRequestInfo have the following
  meanings:

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






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

       o    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
            X.509's rsa and PKCS #1's rsaEncryption. The information
            also includes a bit-string representation of the entity's
            public key.  For both public-key algorithms just mentioned,
            the bit string contains the BER encoding of a value of
            X.509/PKCS #1 type RSAPublicKey.

       o    attributes is a set 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 that the certificate revocation. Another
            example is the extended-certificate-attributes attribute,
            which specifies attributes for a PKCS #6 extended
            certificate.

6.2 CertificationRequest

  A certification request shall have ASN.1 type CertificationRequest:

  CertificationRequest ::= SEQUENCE {
    certificationRequestInfo CertificationRequestInfo,
    signatureAlgorithm SignatureAlgorithmIdentifier,
    signature Signature }

  SignatureAlgorithmIdentifier ::= AlgorithmIdentifier

  Signature ::= BIT STRING

  The fields of type CertificationRequest have the following meanings:

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

       o    signatureAlgorithm identifies the signature
            algorithm (and any associated parameters) under
            which the certification-request information is
            signed. Examples include PKCS #1's
            md2WithRSAEncryption and md5WithRSAEncryption.



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

  The signature process consists of two steps:

       1.   The value of the certificationRequestInfo field 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. The syntax for CertificationRequest could equivalently be
  written with the X.509 SIGNED macro:

  CertificationRequest ::= SIGNED CertificateRequestInfo

Security Considerations

  Security issues are discussed throughout this memo.

Revision history

  Version 1.0

  Version 1.0 is the initial version.

Acknowledgements

  This document is based on a contribution of RSA Laboratories, a
  division of RSA Data Security, Inc.  Any substantial use of the text
  from this document must acknowledge RSA Data Security, Inc. RSA Data
  Security, Inc.  requests that all material mentioning or referencing
  this document identify this as "RSA Data Security, Inc. PKCS #10".

Author's Address

  Burt Kaliski
  RSA Laboratories East
  20 Crosby Drive
  Bedford, MA  01730

  Phone: (617) 687-7000
  EMail: [email protected]





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Full Copyright Statement

  Copyright (C) The Internet Society (1998).  All Rights Reserved.

  This document and translations of it may be copied and furnished to
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  or assist in its implementation may be prepared, copied, published
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  TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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  MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























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