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8 articles in this category.
A5/1 protected GSM phone calls for decades. Learn how three small shift registers that move at irregular times produce keystream, why the cipher was kept secret, and how researchers broke it in practice.
16 min read
E0 is the stream cipher that has protected Bluetooth connections since the late 1990s. Learn how four shift registers and a tiny state machine produce keystream, how the session key and clock are loaded, and why E0 is now considered broken.
20 min read
Grain pairs a linear shift register with a nonlinear one and filters them into a keystream. Learn how Grain v1 and Grain-128 work, why they were designed for tiny hardware, and what attacks have taught designers about them.
17 min read
Rabbit is a fast software stream cipher from Cryptico, and it was one of the winners of the eSTREAM competition. Learn how eight counters, eight state words, and one squaring trick turn a 128-bit key into a stream of keystream blocks.
17 min read
SEAL is a stream cipher that lets you jump to any position in its keystream. Learn how it uses the SHA-1 compression function to build tables from a 160-bit key, and how a few additions and lookups per word make it fast on 32-bit processors.
17 min read
Trivium is one of the smallest strong stream ciphers ever designed. Learn how three shift registers, a few XORs, and three AND gates build a cipher that fits in about 3,500 gates and made it into the eSTREAM hardware portfolio.
13 min read
RC4 was the simplest, fastest cipher of its era. It powered SSL, WEP, and WPA for over a decade before a decade of accumulating bias attacks quietly killed it. Learn how it works and exactly why it's insecure today.
8 min read
Designed by Daniel J. Bernstein as a fast, secure, RC4-free alternative for software encryption, ChaCha20 now secures TLS 1.3 and WireGuard alike. Learn how its add-rotate-XOR "quarter round" builds a full cipher from pure arithmetic.
9 min read
