ChaCha20

Stream cipher. 20 rounds of ARX (add-rotate-XOR). ~1 GB/s software. Constant-time by construction. No lookup tables.

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Poly1305

Universal hash MAC. Sum polynomial evaluated at secret point mod 2^130 - 5. One-time key per message.

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AEAD combination

ChaCha20 encrypts. Derived key authenticates ciphertext + associated data via Poly1305. Single primitive.

Deployment

TLS 1.3 mandatory cipher suite. Chrome uses on mobile (no AES-NI on ARM). WireGuard, Signal, SSH.