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6 articles in this category.
GMAC is the authentication-only mode of AES-GCM. It authenticates data with a polynomial hash over the field GF(2^128), masked by an AES-encrypted counter. Learn how GHASH works, why an IV must never repeat, and how a repeated IV reveals the hash key.
20 min read
KMAC is the message authentication code built on SHA-3. It needs no HMAC-style double hashing, because the Keccak sponge resists length extension. Learn how cSHAKE, the key block, and the encoded output length work, with every NIST sample checked.
17 min read
Poly1305 is a fast one-time message authentication code that evaluates a polynomial modulo 2^130 - 5. Learn how its key is clamped, how each block joins the accumulator, why a key must never be reused, and how an attacker could recover it if it were.
14 min read
UMAC is a very fast message authentication code built on universal hashing. A three-layer hash shrinks the message, and an AES-made pad hides the result. Learn how NH, POLY, and the inner product work, and how forging odds of 2^-30 to 2^-120 are guaranteed.
20 min read
What if you already have AES in your system and don't want to bring in a separate hash function just for message authentication? CMAC builds a MAC directly from a block cipher instead.
9 min read
A hash alone can't prove a message wasn't tampered with. Anyone can recompute it. HMAC fixes that by mixing in a secret key, becoming one of the most quietly essential building blocks in TLS, SSH, and beyond.
8 min read
