LEVIATHAN is a

stream cipher stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream ( keystream). In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystrea ...

submitted to

NESSIE NESSIE (New European Schemes for Signatures, Integrity and Encryption) was a European research project funded from 2000 to 2003 to identify secure cryptographic primitives. The project was comparable to the NIST AES process and the Japanese Go ...

Scott Fluhrer Scott may refer to: Places Canada * Scott, Quebec, municipality in the Nouvelle-Beauce regional municipality in Quebec * Scott, Saskatchewan, a town in the Rural Municipality of Tramping Lake No. 380 * Rural Municipality of Scott No. 98, Sas ...

and David McGrew. It is a seekable stream cipher, which means that the user may efficiently skip forward to any part of the

keystream In cryptography, a keystream is a stream of random or pseudorandom characters that are combined with a plaintext message to produce an encrypted message (the ciphertext). The "characters" in the keystream can be bit The bit is the most basic ...

, much like

CTR mode CTR may refer to: Engineering, science and technology * Counter mode (CTR mode), a cryptographic mode of operation for block ciphers * X-ray crystal truncation rod, a technique to measure properties of crystal surfaces * Current transfer ratio, ...

Salsa20 Salsa20 and the closely related ChaCha are stream ciphers developed by Daniel J. Bernstein. Salsa20, the original cipher, was designed in 2005, then later submitted to the eSTREAM European Union cryptographic validation process by Bernstein. Ch ...

, but unlike those ciphers generating contiguous blocks of the keystream is made especially efficient by LEVIATHAN's unique tree structure based stream generation. LEVIATHAN achieves around 11

cycles per byte Encryption software is software that uses cryptography to prevent unauthorized access to digital information. Cryptography is used to protect digital information on computers as well as the digital information that is sent to other computers over t ...

on a

Pentium II The Pentium II is a brand of sixth-generation Intel x86 microprocessors based on the P6 (microarchitecture), P6 microarchitecture, introduced on May 7, 1997. It combined the ''P6'' microarchitecture seen on the Pentium Pro with the MMX (instruc ...

processor. LEVIATHAN is considered broken due to

distinguishing attack In cryptography, a distinguishing attack is any form of cryptanalysis on data encrypted by a cipher that allows an attacker to distinguish the encrypted data from random data. Modern symmetric-key ciphers are specifically designed to be immune to s ...

s which require 2³⁶ bytes of output and comparable effort.

External links

LEVIATHAN specification
( ZIP file) — link dead
Available from the Internet Archive

References

Stream ciphers {{crypto-stub