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#Poly1305

2 articles with this tag.

Message Authentication Codes Intermediate

The Poly1305 Algorithm

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

Authenticated Encryption (AEAD) Intermediate

The XChaCha20-Poly1305 Algorithm

XChaCha20-Poly1305 extends ChaCha20-Poly1305 with a 192-bit nonce, so you can simply pick a random nonce for every message. Learn how HChaCha20 builds a fresh subkey, how the rest of the AEAD works, and why the bigger nonce makes collisions a non-issue.

15 min read

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