stream cipher

cryptography

A cipher that generates a keystream and XORs it over the data - any length, no blocks, no padding.

ChaCha20 (RFC 8439, paired with Poly1305) is the modern member: constant-time in software and faster than AES on hardware without acceleration, which is why mobile fleets favor it. Its infamous predecessor RC4 accumulated keystream biases until RFC 7465 banned it from TLS entirely.

Also known as: stream cipher, stream ciphers, keystream

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