Poly1305 is a fundamentally different class of authenticator than HMAC-SHA256: the addition of an nonce into the function makes it unsuitable for some environme

Poly1305 is a fundamentally different class of authenticator than HMAC-SHA256: the addition of an nonce into the function makes it unsuitable for some environments. But given Intel's new instructions, GCM is looking like a more attractive polynomial MAC these days.