New returns a new MAC computing an authentication tag of all data written to it with the given key.

Sum generates an authenticator for msg using a one-time key and puts the 16-byte result into out.

Verify returns true if mac is a valid authenticator for m with the given key.

TagSize is the size, in bytes, of a poly1305 authenticator.

MAC is an io.Writer computing an authentication tag of the data written to it.