!!! Overview[1]
In [cryptography], [{$pagename}] ([PKCS]) is a group of [public Key] cryptography standards devised and published by [RSA] Security Inc, starting in the early [1990s].

The company published the standards to promote the use of the [cryptography] techniques to which they had patents, such as the RSA algorithm, the [Schnorr Signature Algorithm] and several others. Though not industry standards (because the company retained control over them), some of the standards in recent years have begun to move into the "standards-track" processes of relevant standards organizations such as the [IETF] and the [PKIX] working-group.

!! The Standards
* [PKCS #1|PKCS 1]
* PKCS #2 - No longer active as of 2010. Covered RSA encryption of message digests; subsequently merged into [PKCS #1|PKCS 1].
* [PKCS #3|PKCS 3]
* PKCS #4 - No longer active as of 2010. Covered RSA key syntax; subsequently merged into [PKCS #1|PKCS 1].
* [PKCS #5|PKCS 5] - Password-based Encryption Standard which is described in [RFC 2898] and [PBKDF2].
* PKCS #6 - Extended-Certificate Syntax Standard which defined extensions to the old v1 X.509 certificate specification. Obsoleted by v3 of the same.
* [PKCS #7|PKCS 7] - [Cryptographic Message Syntax] Standard is defined in [RFC 2315]. Used to [Digitally Signed] and/or [encrypt] messages under a [PKI]. Used also for [certificate] dissemination (for instance as a response to a [PKCS10] message). Formed the basis for [S/MIME|Secure MIME], which is as of 2010 based on [RFC 5652], an updated [Cryptographic Message Syntax] Standard ([CMS]). Often used for single sign-on.
* [PKCS #8|PKCS 8] - [Asymmetric Key Packages] is described in [RFC 5958]. Used to carry private [certificate] keypairs ([encrypted] or unencrypted).
* [PKCS #9|PKCS 9] - Selected Attribute Types is described in [RFC 2985] which describes selected attribute types for use in [PKCS #6|PKCS 6] extended certificates, [PKCS #7|PKCS 7] digitally signed messages, [PKCS #8|PKCS 8] [Private Key] information, and [PKCS #10|PKCS 10] certificate-signing requests.
* [PKCS #10|PKCS 10] - [Certificate Signing Requests]
* [PKCS #11|PKCS 11] - [Cryptographic Token Interface] which was also known as "[Cryptoki]". An [API] defining a generic interface to [cryptographic] [tokens] (typically [Hardware Security Module]). Often used in single sign-on, [Public Key] [cryptography] and disk [encryption] systems. [RSA] Security has turned over further development of the [PKCS#11|PKCS 11] standard to the [OASIS] [PKCS 11] Technical Committee.
* [PKCS #12|PKCS 12] - 
* PKCS #13 - Apparently abandoned, only reference is a proposal from 1998.
* PKCS #14 - Apparently abandoned, NO documents exist
* [PKCS #15|PKCS 15] - [Cryptographic Token Information Format Standard] which defines a standard allowing users of cryptographic tokens to identify themselves to applications, independent of the application's Cryptoki implementation ([PKCS #11|PKCS 11]) or other API. [RSA] has relinquished IC-card-related parts of this standard to [ISO/IEC 7816-15|ISO 7816].!! More Information
There might be more information for this subject on one of the following:
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* [#1] - [PKCS|Wikipedia:PKCS|target='_blank'] - based on data observed:2015-05-18