auth.KeySize
// KeySize is the size, in bytes, of an authentication key.
const KeySize = 32
auth.Size
// Size is the size, in bytes, of an authenticated digest.
const Size = 32
auth.Sum
// Sum generates an authenticator for m using a secret key and returns the
// 32-byte digest.
func Sum(m []byte, key *[KeySize]byte) *[Size]byte
auth.Verify
// Verify checks that digest is a valid authenticator of message m under the
// given secret key. Verify does not leak timing information.
func Verify(digest []byte, m []byte, key *[KeySize]byte) bool