Optimal asymmetric encryption padding

In cryptography, Optimal Asymmetric Encryption Padding (OAEP) is a padding scheme often used together with RSA encryption. The OAEP algorithm is a form of feistel network which uses a pair of random oracles G and H to process a ciphertext prior to asymmetric encryption. When combined with any secure trapdoor one-way function ${\displaystyle f}$, this processing results in a combined scheme which is provably secure against chosen ciphertext attack. To accomplish this result, OAEP satisfies the following three goals:

1. Add an element of randomness which can be used to convert a deterministic encryption scheme (e.g., traditional RSA) into a probabilistic scheme.
2. Prevent partial decryption of ciphertexts (or other information leakage) by ensuring that an adversary cannot recover any portion of the plaintext without completely defeating the trapdoor one-way function ${\displaystyle f}$.
3. Provide a cryptographic integrity check which guarantees "plaintext awareness", i.e., that no adversary can create a ciphertext without knowing the plaintext. This serves to prevent chosen ciphertext attacks.

See RFC2437 for an outline of how OAEP padding and un-padding works in conjunction with RSA.