Poly1305
Poly1305 is a universal hash family designed by Daniel J. Bernstein for use in cryptography.
As with any universal hash family, Poly1305 can be used as a one-time message authentication code to authenticate a single message using a secret key shared between sender and recipient, similar to the way that a one-time pad can be used to conceal the content of a single message using a secret key shared between sender and recipient.
Originally Poly1305 was proposed as part of Poly1305-AES, a Carter–Wegman authenticator that combines the Poly1305 hash with AES-128 to authenticate many messages using a single short key and distinct message numbers. Poly1305 was later applied with a single-use key generated for each message using XSalsa20 in the NaCl crypto_secretbox_xsalsa20poly1305 authenticated cipher, and then using ChaCha in the ChaCha20-Poly1305 authenticated cipher deployed in TLS on the internet.