Instytut Podstawowych Problemów Techniki

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It is widely believed, that randomness exists in Nature. In fact such an assumption underlies many scientific theories and is embedded in the foundations of quantum mechanics. Assuming that this hypothesis is valid one can use natural phenomena, like radioactive decay, to generate random numbers. Today, computers are capable of generating the so-called pseudorandom numbers. Such series of numbers are only seemingly random (bias in the randomness quality can be observed). Question whether people can produce random numbers, has been investigated by many scientists in the recent years. The paper “Humans can consciously generate random numbers sequences…” published recently in Medical Hypotheses made claims that were in many ways contrary to state of art; it also stated far-reaching hypotheses. So, we decided to repeat the experiments reported, with special care being taken of proper laboratory procedures. Here, we present the results and discuss possible implications in computer and other sciences.

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In the paper we propose a general, abstract framework for Automatic Secret Generation and Sharing (ASGS) that should be independent of underlying Secret Sharing Scheme (SSS). ASGS allows to prevent the Dealer from knowing the secret. The Basic Property Conjecture (BPC) forms the base of the framework. Due to the level of abstraction, results are portable into the realm of quantum computing.

Two situations are discussed. First concerns simultaneous generation and sharing of the random, prior nonexistent secret. Such a secret remains unknown until it is reconstructed. Next, we propose the framework for automatic sharing of a known secret. In this case the Dealer does not know the secret and the secret Owner does not know the shares. We present opportunities for joining ASGS with other extended capabilities, with special emphasis on PVSS and pre-positioned secret sharing. Finally, we illustrate framework with practical implementation.

Słowa kluczowe:

Secret sharing, Security protocols, Dependable systems, Authentication management

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Streszczenie:

The paper is concerned with secret sharing schemes, a family of cryptographic protocols. First, we describe the basic schemes. Next, we present general secret sharing and the approach based on information theory. Finally, we outline extended capabilities of secret sharing schemes. An additional contribution of the paper is our effort to present unified terminology in Polish.

Słowa kluczowe:

cryptography, secret sharing schemes, data security

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Informally speaking, one-way functions are functions for which it is „easy” to compute their values from their arguments but it is „computationally infeasible” to reverse them i.e. to find their arguments knowing their values. A rigorous definition of the terms „easy” and „computationally infeasible” is necessary but would detract from the simple idea that is being conveyed. Existence of one-way functions is only conjectured and closely connected with Cook’s hypothesis. Roughly speaking, if P is not equal NP such functions should exist. Apart from theoretical importance, one-way functions are fundamental for complexity based cryptography. Problem is being attacked in many ways and there are several instances which are perceived to be good candidates, for instance factorisation or discreet logarithm. There are also practical reasons to search for new candidates. We investigate the possibilities of inverting the VMPC one-way function, which was proposed at Fast Software Encryption 2004. (VMPC stands for Variably Modified Permutation Composition). First, we describe the function using the language of permutation theory. Next, easily invertible instances of VMPC are derived. We also show that no VMPC function is one-to-one. Implications of these results for cryptographic applications of VMPC conclude the presentation.

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This paper will concern itself with a formulation of a traffic analysis problem for mobile agents. It is an interesting theoretical problem as well as a critical feature when using agents on a massive scale in decision making systems. The decision making systems are applied to demanding and complex environments such as stock markets. The mobile agents used are natural targets for attacks because they provide information for decision making. The resulting information can have a value measured in millions of dollars and information of such a high value attracts potential attacks. An efficient way to attack the user of decision making systems is to learn her strategy and respond in kind. In this respect even passive observation of agents can provide useful data, namely what information they are gathering. A common first defense is to provide anonymity for mobile agents. However, what happens when anonymity is gone? What information then becomes available and what steps will the user take? Yet, the problem has not been previously formulated for such a framework. We formulate it in terms of various factors used for traffic analysis. These factors originate from different side channels that provide information on the operating agents. At the end we state a paradox, which links an excessive use of countermeasures against traffic analysis with weakening system security.

Słowa kluczowe:

Mobile agents security, security protocols, traffic analysis, side channel attacks

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