Ben Smeets

A Simple Algorithm for Fast Correlation Attacks on Stream Ciphers

A new simple algorithm for fast correlation attacks on stream ciphers is presented. The advantages of the new approach are at least two. Firstly, the new algorithm significantly reduces the memory requirements compared with some recent proposals [2,3]. This allows more powerful attacks than previously. Secondly, the simplicity of the algorithm allows us to derive theoretical results. We determine the relation between the number of observed symbols, the correlation probability, and the allowed computational complexity, required for a successful attack. Hence, we can get theoretical estimates on the required computational complexity in cases when simulation is not possible.

On a fast correlation attack on certain stream ciphers

In this paper we present a new algorithm for the recovery of the initial state of a linear feedback shift register when a noisy output sequence is given. Our work is focussed on the investigation of the asymptotical behaviour of the recovery process rather than on the construction of an optimal recovery procedure. Our results show the importance of low-weight checks and show also that the complexity of the recovery problem grows less than exponentially with the length of the shift register, even if the number of taps grows linearly with the register length. Our procedure works for shift register with arbitrary feedback polynomial.

On families of hash functions via geometric codes and concatenation

In this paper we use coding theory to give simple explanations of some recent results on universal hashing. We first apply our approach to give a precise and elegant analysis of the Wegman-Carter construction for authentication codes. Using Reed-Solomon codes and the well known concept of concatenated codes we can then give some new constructions, which require much less key size than previously known constructions. The relation to coding theory allows the use of codes from algebraic curves for the construction of hash functions. Particularly, we show how codes derived from Artin-Schreier curves, Hermitian curves and Suzuki curves yield good classes of universal hash functions.In this paper we use coding theory to give simple explanations of some recent results on universal hashing. We first apply our approach to give a precise and elegant analysis of the Wegman-Carter construction for authentication codes. Using Reed-Solomon codes and the well known concept of concatenated codes we can then give some new constructions, which require much less key size than previously known constructions. The relation to coding theory allows the use of codes from algebraic curves for the construction of hash functions. Particularly, we show how codes derived from Artin-Schreier curves, Hermitian curves and Suzuki curves yield good classes of universal hash functions.

On the relation between A-codes and codes correcting independent errors

In this paper we show an explicit relation between authentication codes and codes correcting independent errors. This relation gives rise to several upper bounds on A-codes. We also show how to construct A-codes starting from error correcting codes. The latter is used to show that if PS exceeds PI by an arbitrarily small positive amount, then the number of source states grows exponentially with the number of keys but if PS = PI it will grow only linearly.

On the cardinality of systematic authentication codes via error-correcting codes

In both open and private communication the participants face potential threats from a malicious enemy who has access to the communication channel and can insert messages (impersonation attack) or alter already transmitted messages (substitution attack). Authentication codes (A-codes) have been developed to provide protection against these threats. In this paper we introduce a new distance, called the authentication distance (A-distance), and show that an A-code can be described as a code for the A-distance. The A-distance is directly related to the probability P/sub S/ of success in a substitution attack. We show how to transform an error-correcting code into an A-code and vice versa. We further use these transformations to provide both upper and lower bounds on the size of the information to be authenticated, and study their asymptotic behavior. As examples of obtained results, we prove that the cardinality of the source state space grows exponentially with the number of keys provided P/sub S/>P/sub I/, we generalize the square-root bound given by Gilbert, MacWilliams, and Sloane in 1979, and we provide very efficient constructions using concatenated Reed-Solomon codes.

A Digital Signature Scheme Based on Random Error-Correcting Codes

Over the past years there have been few attempts to construct digital signature schemes based on the intractability of the decoding of linear error-correcting codes. Unfortunately all these attempts failed. In this paper we suggest a new approach based on a seemingly unknown before fact that the set of correctable syndroms being nonlinear nevertheless contains a rather large linear subspace.

Fast Message Authentication Using Efficient Polynomial Evaluation

Message authentication codes (MACs) using polynomial evaluation have the advantage of requiring a very short key even for very large messages. We describe a low complexity software polynomial evaluation procedure, that for large message sizes gives a MAC that has about the same low software complexity as for bucket hashing but requires only small keys and has better security characteristics.

Privacy, Security and Trust in Cloud Computing: The Perspective of the Telecommunication Industry

The telecommunication industry has been successful in turning the Internet into a mobile service and stimulating the creation of a new set of networked, remote services. In this paper we argue that embracing cloud computing solutions is fundamental for the telecommunication industry to remain competitive. However, there are legal, regulatory, business, market related and technical challenges that must be considered. In this paper we list such challenges and define a set of privacy, security and trust requirements that must be taken into account before cloud computing solutions can be fully integrated and deployed by telecommunication providers.

On the construction of authentication codes with secrecy and codes withstanding spoofing attacks of order L ≥2

We present an analysis of some known Cartesian authentication codes and their modification into authentication codes with secrecy, with transmission rate R = r/n, where n = 2, 3, . . . , and 1 ? r ? n - 1 using (n - r)(r + 1) q-ary key digits. For this purpose we use a grouping technique.Essentially the same key grouping technique is used for the construction of codes that withstand spoofing attacks of order L ? 2. The information rate of this scheme is also r/n, and it requires (L + r)(n - r) q-ary key digits. Moreover these codes allow that previously transmitted source states can be reused.

Unconditionally Secure Group Authentication

Group authentication schemes as introduced by Boyd and by Desmedt and Frankel are cryptographic schemes in which only certain designated groups can provide messages with authentication information. In this paper we study unconditionally secure group authentication schemes based on linear perfect secret sharing and authentication schemes, for which we give expressions for the probabilities of successful attacks. Furthermore, we give a construction that uses maximum rank distance codes.