Trivium (cipher)

Trivium is a synchronous stream cipher designed by Christophe De Cannière and Bart Preneel to offer a flexible trade-off between speed and gate count in hardware while remaining reasonably efficient in software. It was submitted to the hardware profile of the eSTREAM competition, was chosen for the eSTREAM portfolio of low-area hardware ciphers, is not patented and is specified in the international standard ISO/IEC 29192-3. From an 80-bit key and an 80-bit initialisation vector it can produce up to 2 to the power 64 bits of output. Its 288-bit internal state is three shift registers updated by a few XOR and AND operations, and the state is run for 1152 rounds before any output appears. It is the simplest eSTREAM entrant, and as of 2025 no attack better than brute force is known against the full cipher, although attacks on reduced-round versions come close.