Editing Padding (cryptography) (section)

==Public key cryptography==
In [[public key cryptography]], padding is the process of preparing a message for encryption or signing using a specification or scheme such as [[PKCS1|PKCS#1]] v2.2, [[OAEP]], [[Probabilistic signature scheme|PSS]], PSSR, IEEE P1363 EMSA2 and EMSA5.  A modern form of padding for asymmetric primitives is [[Optimal Asymmetric Encryption Padding|OAEP]] applied to the [[RSA (algorithm)|RSA algorithm]], when it is used to encrypt a limited number of bytes.

The operation is referred to as "padding" because originally, random material was simply appended to the message to make it long enough for the primitive. This form of padding is not secure and is therefore no longer applied.  A modern padding scheme aims to ensure that the attacker cannot manipulate the plaintext to exploit the mathematical structure of the primitive and will usually be accompanied by a proof, often in the [[random oracle model]], that breaking the padding scheme is as hard as solving the hard problem underlying the primitive.