Keyak is an authenticated encryption scheme based on Keccak-p. It takes as input a *secret and unique value* (SUV), then some associated data (or metadata) that are authenticated but not encrypted and finally some plaintext. It produces a cryptogram comprising the ciphertext and a tag authenticating both the metadata and the plaintext. The recipient holding the same secret key can decrypt the cryptogram and check whether it is authentic.

Keyak supports also the concept of sessions. Without having to input the key again and a new nonce, the communicating parties can keep on exchanging metadata-plaintext pairs. Each time, the tag authenticates the complete exchange of messages so far. The SUV can be either a secret key and a nonce, or a one-time session key derived using public-key cryptographic techniques.

Keyak provides strong bounds against generic attacks and uses the well-analyzed Keccak-p permutation. It aims at robustness and performance on a wide range of processors.