Описание тега pkcs#1
PKCS #1 is a standard that defines the RSA algorithm and padding schemes.
PKCS #1 is a security standard, published by RSA Security, which describes the RSA algorithm and padding schemes. The current version, PKCS #1 v2.1, is also available as RFC 3447.
Besides the RSA algorithm, PKCS #1 v2.1 defines the OAEP padding scheme for encryption, the PSS padding scheme for signature, and the legacy PKCS1-v1.5 scheme for encryption and signature. PKCS #1 also defines an ASN.1 asn.1 syntax for RSA keys.