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In this article we present some weaknesses in the RC4 cipher and their cryptographic applications. Especially we improve the attack described in [2] in such a way, that it will work, if the weak keys described in that paper are avoided. A further attack will work even if the first 256 Byte of the output remain unused. Finally we show that variants of the… (More)

We present improved lower bounds on the sizes of small maximal partial ovoids and small maximal partial spreads in the classical sym-plectic and orthogonal polar spaces, and improved upper bounds on the sizes of large maximal partial ovoids and large maximal partial spreads in the classical symplectic and orthogonal polar spaces. An overview of the status… (More)

We start by defining generalised dual arcs, the motivation for defining them comes from cryptography, since they can serve as a tool to construct authentication codes and secret sharing schemes. We extend the charac-terisation of the tangent planes of the Veronesean surface V 4 2 in P G(5, q), q odd, described in [4], as a set of q 2 + q + 1 planes in P… (More)

One-way cellular automata with restricted nondeterminism are investigated. The number of allowed nondeterministic state transitions is limited to a constant. It is shown that a limit to exactly one step does not decrease the language accepting capabilities. We prove a speed-up result that allows any linear-time computation to be sped-up to real-time. Some… (More)

Space-bounded one-way cellular language acceptors (OCA) are investigated. The only inclusion known to be strict in their time hierarchy from real-time to exponential time is between real-time and linear-time! We show the surprising result that there exists an infinite hierarchy of properly included OCA-language families in that range. A generalization of a… (More)

Space-bounded one-way cellular language acceptors (OCA) are investigated. The only inclusion known to be strict in their time hierarchy from real-time to exponential-time is between real-time and linear-time! We show the surprising result that there exists an infinite hierarchy of properly included OCA-language families in that range. A generalization of a… (More)

An iterative array is a line of interconnected interacting finite automata. One distinguished automaton, the communication cell, is connected to the outside world and fetches the input serially symbol by symbol. Sometimes in the literature this model is referred to as cellular automaton with sequential input mode. We are investigating iterative arrays with… (More)

Deterministic k-tape and multitape Turing machines with one-way, two-way and without a separated input tape are considered. We investigate the classes of languages acceptable by such devices with time bounds of the form n + r(n) where r ∈ o(n) is a sublinear function. It is shown that there exist infinite time hierarchies of separated complexity classes in… (More)

One-way and two-way cellular language acceptors with restricted nondeterminism are investigated. The number of nondeterministic state transitions is regarded as limited resource which depends on the length of the input. We center our attention to real-time, linear-time and unrestricted-time computations. A speed-up result that allows any linear-time… (More)