PKCS, Public-Key Cryptography Standards

Description Glossary RFCs Publications Obsolete RFCs


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RFC 3447:

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 and IEEE P1363 documents, PKIX, SET, S/MIME, SSL/TLS, and WAP/WTLS.


Asymmetric Cryptography.
(RFC 2828) A modern branch of cryptography, popularly known as "public-key cryptography", in which the algorithms employ a pair of keys and use a different component of the pair for different steps of the algorithm.

CA, Certification Authority.
(RFC 2828) An entity that issues digital certificates and vouches for the binding between the data items in a certificate.

CM, Certificate Management.
(RFC 2828) The functions that a CA may perform during the life cycle of a digital certificate, including the following:

CPS, Certification practice statement.
(RFC 2828) A CPS is a published security policy that can help a certificate user to decide whether a certificate issued by a particular CA can be trusted enough to use in a particular application. A CPS may be:

A CPS is usually more detailed and procedurally oriented than a certificate policy. A CPS applies to a particular CA or CA community, while a certificate policy applies across CAs or communities. A CA with a single CPS may support multiple certificate policies, which may be used for different application purposes or by different user communities. Multiple CAs, each with a different CPS, may support the same certificate policy.

CRL, Certificate Revocation List.

Digital Certificate.
(RFC 2828) A certificate document in the form of a digital data object (a data object used by a computer) to which is appended a computed digital signature value that depends on the data object.

Digital Signature.
(RFC 2828) A value computed with a cryptographic algorithm and appended to a data object in such a way that any recipient of the data can use the signature to verify the data's origin and integrity.

DN, Distinguished Name.
(RFC 2828) An identifier that uniquely represents an object in the X.500 DIT, Directory Information Tree. A Distinguished Name is a set of attribute values that identify the path leading from the base of the DIT to the object that is named. An X.509 public-key certificate or CRL contains a DN that identifies its issuer, and an X.509 attribute certificate contains a DN or other form of name that identifies its subject.

PKCS #1: RSA Cryptography Specifications.

PKCS #5: Password-Based Cryptography Specification.

PKCS #7: Cryptographic Message Syntax.
Defines a syntax for data that may have cryptography applied to it, such as for digital signatures and digital envelopes.

PKCS #9: Selected Object Classes and Attribute Types.

PKCS #10: Certification Request Syntax.
Defines a syntax for requests for public-key certificates. A certification request contains a DN and a public key, and may contain other attributes, and is signed by the entity making the request. The request is sent to a CA who converts it to an X.509 public-key certificate (or some other form) and returns it, possibly in PKCS #7 format.

PKCS #11.
Defines the software CAPI for devices that hold cryptographic information and perform cryptographic functions. The API software is known as the cryptographic application programming interface (CAPI or Crypto API). The source code formats and procedures through which an application program accesses cryptographic services, which are defined abstractly compared to their actual implementation.

PKI, Public-Key Infrastructure.
(RFC 2828) A system of CAs and, optionally, RAs and other supporting servers and agents that perform some set of certificate management, archive management, key management, and token  management functions for a community of users in an application of asymmetric cryptography. The set of hardware, software, people, policies, and procedures needed to create, manage, store, distribute, and revoke digital certificates based on asymmetric cryptography. The core PKI functions are:

Key pairs for data confidentiality may be generated, and perhaps escrowed, by CAs or RAs, but requiring a PKI client to generate its own digital signature key pair helps maintain system integrity of the cryptographic system, because then only the client ever possesses the private key it uses. Also, an authority may be established to approve or coordinate CPSs, which are security policies under which components of a PKI operate. A number of other servers and agents may support the core PKI, and PKI clients may obtain services from them. The full range of such services is not yet fully understood and is evolving, but supporting roles may include archive agent, certified delivery agent, confirmation agent, digital notary, directory, key escrow agent, key generation agent, naming agent who ensures that issuers and subjects have unique identifiers within the PKI, repository, ticket-granting agent, and time stamp agent.

Private Key.
(RFC 2828) The secret component of a pair of cryptographic keys used for asymmetric cryptography. In a public key cryptosystem that key of a user's key pair which is known only by that user.

Public Key.
(RFC 2828) The publicly-discloseable component of a pair of cryptographic keys used for asymmetric cryptography. In a public key cryptosystem that key of a user's key pair which is publicly known.

Public-Key Certificate.
(RFC 2828) A digital certificate that binds a system entity's identity to a public key value, and possibly to additional data items; a digitally-signed data structure that attests to the ownership of a public key. The digital signature on a public-key certificate is unenforgeable. Thus, the certificate can be published, such as by posting it in a directory, without the directory having to protect the certificate's data integrity. The public key of a user, together with some other information, rendered unenforgeable by encipherment with the private key of the certification authority which issued it.

RA, Registration authority.
(RFC 2828) An optional PKI entity, separate from the CAs, that does not sign either digital certificates or CRLs but has responsibility for recording or verifying some or all of the information, particularly the identities of subjects, needed by a CA to issue certificates and CRLs and to perform other certificate management functions.


[RFC 2315] PKCS #7: Cryptographic Message Syntax Version 1.5.

[RFC 2898] PKCS #5: Password-Based Cryptography Specification Version 2.0.

[RFC 2985] PKCS #9: Selected Object Classes and Attribute Types Version 2.0.

[RFC 2986] PKCS #10: Certification Request Syntax Specification Version 1.7.

[RFC 3447] Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1.


Obsolete RFCs:

[RFC 2313] PKCS #1: RSA Encryption Version 1.5.

[RFC 2314] PKCS #10: Certification Request Syntax Version 1.5.

[RFC 2437] PKCS #1: RSA Cryptography Specifications Version 2.0.

Description Glossary RFCs Publications Obsolete RFCs