PKCS 1

In cryptography, PKCS #1 is the first of a family of standards called Public-Key Cryptography Standards (PKCS), published by RSA Laboratories. It provides the basic definitions of and recommendations for implementing the RSA algorithm for public-key cryptography. It defines the mathematical properties of public and private keys, primitive operations for encryption and signatures, secure cryptographic schemes, and related ASN.1 syntax representations.

The current version is 2.2 (2012-10-27). Compared to 2.1 (2002-06-14), which was republished as RFC 3447, version 2.2 updates the list of allowed hashing algorithms to align them with FIPS 180-4, therefore adding SHA-224, SHA-512/224 and SHA-512/256.

The PKCS #1 standard defines the mathematical definitions and properties that RSA public and private keys must have. The traditional key pair is based on a modulus, ${\displaystyle n}$, that is the product of two distinct large prime numbers, ${\displaystyle p}$ and ${\displaystyle q}$, such that ${\displaystyle n=pq}$.

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