Improved Distinguishers on Stream Cipher Achterbahn-v2

The Achterbahn Stream Cipher

ACHTERBAHN: A Proposal for a Profile 2 Stream Cipher to ECRYPT’s Call for Stream Cipher Primitives

We propose a new additive binary stream cipher called Achterbahn. The keystream generator (KSG) consists of eight primitive binary nonlinear feedback shift registers (NLFSR’s). A binary N -stage feedback shift register is called primitive if it has a cycle of length 2N − 1 containing all binary nonzero N tuples. Each shift register has a configurable linear feedforward output function. The outp...

Cryptanalysis of the Stream Cipher ABC v2

ABC v2 is a software-efficient stream cipher with 128-bit key. In this paper, we apply a fast correlation attack to break ABC v2 with weak keys. There are about 2 weak keys in ABC v2. The complexity to identify a weak key and to recover the internal state of a weak key is low: identifying one weak key from about 2 random keys requires 6460 keystream bytes and 2 operations for each random key. R...

An Improved Attack on WG Stream Cipher

WG is a synchronous stream cipher submitted to the hardware profile of eSTREAM project. The main feature of this stream cipher is the use of WG transformation. WG uses keys and initial vectors (IVs) of the same lengths 80, 96, 112 and 128 bits. Moreover, IVs of the length 32 and 64 bits are admitted. The most important key recovery attack on WG was presented by Wu and Preneel and uses the weakn...

Fruit-v2: Ultra-Lightweight Stream Cipher with Shorter Internal State

A few lightweight stream ciphers were introduced for hardware applications in the eSTREAM project. In FSE 2015, while presenting a new idea (i.e. the design of stream ciphers with the shorter internal state by using a secret key, not only in the initialization but also in the keystream generation), Sprout was proposed. Unfortunately, Sprout is insecure. Because Grain-v1 is the lightest cipher i...