PKCS #10 v1.5: PKCS #10: Certification Request Syntax Version 1.5
The format for requesting a digital certificate from a certificate authority.
Kaliski, B., "PKCS #10: Certification Request Syntax Version 1.5", RFC 2314, DOI 10.17487/RFC2314, March 1998, <https://www.rfc-editor.org/info/rfc2314>.
@misc{rfc2314,
series = {Request for Comments},
number = 2314,
howpublished = {RFC 2314},
publisher = {RFC Editor},
doi = {10.17487/RFC2314},
url = {https://www.rfc-editor.org/info/rfc2314},
author = {B. Kaliski},
title = {{PKCS #10: Certification Request Syntax Version 1.5}},
pagetotal = 8,
year = 1998,
month = mar,
} RFC text
Contents
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.
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.
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.
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.
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.
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.
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: burt@rsa.com
Full Copyright Statement
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AI ELI5
On this page
§1Certificate Requests Explained
A certification request is a message sent by a person or system to ask a certificate authority (CA) to issue a digital certificate. The request contains the entity's distinguished name (a unique identifier), the entity's public key, and optionally additional information such as a postal address, email, or a challenge password for later certificate revocation.
The certificate authority receives the request, verifies that the signature is valid (proving the requester has the corresponding private key), and then creates an X.509 certificate binding the requester's name and public key together with the CA's own signature. The CA may also include additional information such as serial number, validity period, and signature algorithm in the final certificate. How the CA returns the certificate is outside the scope of this specification.
This memo defines the syntax for certification requests. It is an informational publication of RSA Laboratories' PKCS #10 standard, intended to enable interoperability across systems that need to request and process certificates.
You want a signed ID card from a trusted place. You tell them your name, your public code, and some extra info. You sign it with your secret code to prove it really is you. The office checks the signature and makes your ID card.
§2The Three Parts of a Request
A certification request consists of three main parts. The first is certification request information, which contains the entity's distinguished name, public key information, and optional attributes. The second is a signature algorithm identifier specifying which algorithm (such as MD5-with-RSA or MD2-with-RSA) is used to sign the request. The third is the actual digital signature of the request information, created using the entity's private key.
The certification request information itself has four fields: version (0 for this version), subject name (the distinguished name of the entity requesting the certificate), subject public key information (which includes the algorithm and the actual public key bits), and attributes (an optional set of additional information).
The attributes field can contain various information useful to the certificate authority. PKCS #9 defines many standard attribute types, including the challenge password (used for later revocation requests), extended certificate attributes (for X.509 extended certificates), and other metadata about the subject.
Your request is three parts: details (your name, your public code, and extra info), how you signed it (which math you used), and your actual signature. The details get signed with your secret code.
§3Security Properties and Verification
The signature on the certification request prevents an entity from requesting a certificate with another party's public key. Without the signature requirement, an attacker could potentially submit a request with someone else's name and public key, creating a fraudulent certificate. The signature proves possession of the corresponding private key, since only the entity with that private key can produce a valid signature over the request information.
The signature must be verified before a certificate is issued. The certificate authority uses the public key information in the request to verify that the signature is valid. If the signature is invalid, the request is rejected. The certificate authority may also perform additional validation such as verifying the requester's identity through out-of-band means, consulting X.500 directory services, or requiring additional documentation.
For ASN.1 encoding, the request information is first converted to Distinguished Encoding Rules (DER), a binary encoding format, and then that octet string is signed. This ensures that the exact binary representation is signed, preventing interpretation ambiguities.
Your signature on the form proves it's really you asking, not someone pretending to be you. The office checks your signature against your public code before making your certificate.
§4How Certificate Authorities Process Requests
When a certificate authority receives a certification request, it performs several steps. First, it verifies the signature over the certification request information using the public key included in the request. If the signature is invalid, the request is rejected immediately.
If the signature is valid, the CA constructs an X.509 public-key certificate from the distinguished name and public key in the request. The CA adds its own information to the certificate, including: the CA's own distinguished name (as issuer), a serial number chosen by the CA, a validity period (start and end dates), and the signature algorithm the CA will use to sign the certificate. The CA then signs the complete certificate with its own private key.
If the request contains a PKCS #9 extended-certificate-attributes attribute, the CA may also create a PKCS #6 extended certificate. The certificate authority may return the new certificate in various forms, including as a PKCS #7 cryptographic message, a central database record, or with additional certificates such as cross-certificates or certificate revocation lists (CRLs).
The office checks your signature. If it's good, it takes your name and public code, adds their own signature, and makes your ID card. They might give you extra stuff like the chain of trust or other ID cards you need.
- Certification Request (signed)Name, public key, attributes, signature
- X.509 Certificate (CA-signed)If signature is valid
§5Usage in Practice
A typical entity first generates a public-key/private-key pair (such as an RSA key pair). It then creates a certification request by bundling its distinguished name, the public key, optional attributes such as a challenge password, and a signature created with the private key. The entity sends this request to a certificate authority.
The choice of how to send the request is flexible. Both electronic and paper forms are possible. Electronic forms might use email, HTTP, or proprietary protocols. Paper forms might be printed and sent by post. This specification focuses only on the format of the request itself, not the transport mechanism.
Common attributes included in requests are the challenge password (allowing the entity to later request revocation by proving knowledge of the password), postal address (for the CA to return the certificate by mail if electronic delivery fails), and extended certificate attributes. The request format allows for flexibility: optional attributes provide additional information where needed, while the core structure remains compact to minimize request size, which is important for CAs that accept requests on paper.
You make a public/private key pair, create the form with your name, key, and signature, and send it to the office. You can email it, mail it, or use a web form. The office gets the form in whatever way works for you.