Grain and Trivium are two hardware oriented synchronous stream ciphers proposed as the simplest candidates to the ECRYPT Stream Cipher Project, both dealing with 80-bit secret keys. In this paper we apply the linear sequential circuit approximation method to evaluate the strength of these stream ciphers against distinguishing attack. In this approximation method which was initially introduced b...

Feedback with Carry Shift Registers (FCSRs) are a promising alternative to Linear Feedback Shift Registers (LFSRs) for the design of stream ciphers. The main difference between these two automata lies in the computation of the feedback. While LFSRs use simple bitwise addition, FCSRs use addition with carries. Hence, the transition function of an FCSR is non-linear, more precisely quadratic. Sin...

Feedback with Carry Shift Registers (FCSRs) have previously been available in two configurations, the Fibonacci and Galois architectures. Recently, a generalized and unifying FCSR structure and theory was presented. The new ring FCSRs model repairs some weaknesses of the older architectures. Most notably, the carry cell bias property that was exploited for an attack on the eSTREAM final portfol...

This paper presents a new class of cryptanalytic attacks, which are applicable against those binary additive synchronous stream ciphers, whose analysis theory is based on the properties of 2-adic numbers. These attacks are named as ‘Linearisation Attacks’. Linearisation attacks consist of three variants, which are referred as ‘Conventional Linearisation Attacks (CLAs)’, ‘Fast Linearisation Atta...

One of the eSTREAM final portfolio ciphers is the hardwareoriented stream cipher Trivium. It is based on 3 nonlinear feedback shift registers with a linear output function. Although Trivium has attached a lot of interest, it remains unbroken by passive attacks. At FSE 2008 a differential fault analysis of Trivium was presented. It is based on the fact that one-bit fault induction reveals many p...

Grain v1 is one of the 7 finalists selected in the final portfolio by the eSTREAM project. It has an elegant and compact structure, especially suitable for a constrained hardware environment. Though a number of potential weaknesses have been identified, no key recovery attack on the original design in the single key model has been found yet. In this paper, we propose a key recovery attack, call...

Since the security analysis against stream ciphers becomes more difficult nowadays, it is urgent and significant to propose new generic methods. In this work, we introduce guess-and-determine techniques to two traditional analysis methods and make the new approaches methodological for generalization. We show the power of the new methods by analyzing two stream ciphers: Grain-v1 and ACORN. Grain...

Abstract Grain is one of the simplest ECRYPT Stream Cipher project Candidates which deals with key and IV of length 80 and 64 respectively. Using the linear sequential circuit approximation method, introduced by Golic in 1994, we derive a linear function of consecutive keystream bits which is held with correlation coefficient of about 2. Then using the concept of so-called generating function, ...

Stream ciphers are cryptographic primitives that ensure the confidentiality of communications. In this thesis, we study several attacks on stream ciphers. For practical applications, the candidates of stream ciphers of NESSIE and eSTREAM projects are scrutinized. Firstly, the algebraic attacks on SOBER-t32 and SOBER-t16 stream ciphers are performed under the assumption that the stuttering phase...

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