of_key k converts k to storage. The result is key_size bytes long.

to_key s converts s to a secret key.

• raises Size_mismatch

  if s is not key_size bytes long

of_auth a converts a to storage. The result is auth_size bytes long.

to_auth s converts s to an authenticator.

• raises Size_mismatch

  if s is not auth_size bytes long

auth k m authenticates a message m using a secret key k, and returns an authenticator a.

verify k a m checks that a is a correct authenticator of a message m under the secret key k.

• raises Verification_failure

  if a is not a correct authenticator of m under k