The Public-Key Cryptography Standards (PKCS) are specifications produced by RSA® Laboratories. The documents were first published in 1991 as a result of meetings with a small group of early adopters of public-key technology. RSA Laboratories worked with developers through a collaborative process of mailing list discussions and workshops to develop these standards to accelerate the use public-key or asymmetric cryptography.

Although the PKCS specifications are not published by an independent standards organization, they are widely used. And 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. The documents are maintained by RSA Security.