Auswahl der wissenschaftlichen Literatur zum Thema „Two-wayness“

The braid group cryptography arises with the involvement of the braid group, which is an infinite non-commutative group arising from geometric braids. In this paper, we have proposed a new public key cryptosystem based on braid group. The security of our proposed scheme is based on two hard problems on braid group, conjugacy search problem and p-th root problem on braid group. We also checked the one-wayness, semantic security and efficiency of our proposed scheme, and found it to be computationally secured

At Eurocrypt ’99, Paillier showed a cryptographic application of the group [Formula: see text], the multiplicative group modulo [Formula: see text] where [Formula: see text] is some RSA modulus. In this paper, we have present a new public key cryptosystem over [Formula: see text] where [Formula: see text] is a product of two safe primes, which is based on two intractable problems namely, integer factorization and partial discrete logarithm problem over [Formula: see text], the group of quadratic residues modulo [Formula: see text]. This scheme is a combination of BCP (Bresson–Catalano–Pointcheval) cryptosystem, proposed by Bresson et al. at Asiacrypt ’03 and the Rabin–Paillier scheme proposed by Galindo et al. at PKC 2003. We will show that the one-wayness of this new scheme equally depends on the Computational Diffie–Hellman assumption and factoring assumption. We will also prove that the proposed scheme is more secure than the BCP cryptosystem and the Rabin–Paillier cryptosystem.

Abstract In this article, I advocate the reconceptualisation of ‘integration as a two-way process’. I argue that integration is, fundamentally, an issue of relational inequality, and conceptualising it as a one-way process constitutes problems of undesirability and infeasibility. I show the theoretical hiatus which characterises many dominant approaches to the two-way process, which leads scholars to build their work on internal contradictions and to implicitly (and often unintentionally) feed into a one-way integration discourse. I argue that as long as conceptualisations of integration as a two-way process reinforce a boundary between ‘people who integrate’ and ‘people who do not integrate’, they are unfit to avoid the problems of one-wayness which they intended to overcome in the first place. In the last part of the article, I put forward some initial building blocks for a new theoretical framework of ‘integration as a two-way process’ which is more attentive to the relational social processes that constitute integration.

This PhD is about two natural extensions of Finite Automata (FA): the 2-way fa (2FA) and the 2-way transducers (2T). It is well known that 2FA s are computably equivalent to FAs, even in their nondeterministic (2nfa) variant. However, in the field of descriptional complexity, some questions remain. Raised by Sakoda and Sipser in 1978, the question of the cost of the simulation of 2NFA by 2DFA (the deterministic variant of 2FA) is still open. In this manuscript, we give an answer in a restricted case in which the nondeterministic choices of the simulated 2NFA may occur at the boundaries of the input tape only (2ONFA). We show that every 2ONFA can be simulated by a 2DFA of subexponential (but superpolynomial) size. Under the assumptions L=NL, this cost is reduced to the polynomial level. Moreover, we prove that the complementation and the simulation by a halting 2ONFA is polynomial. We also consider the anologous simulations for alternating devices. Providing a one-way write-only output tape to FAs leads to the notion of transducer. Contrary to the case of finite automata which are acceptor, 2-way transducers strictly extends the computational power of 1-way one, even in the case where both the input and output alphabets are unary. Though 1-way transducers enjoy nice properties and characterizations (algebraic, logical, etc. . . ), 2-way variants are less known, especially the nondeterministic case. In this area, this manuscript gives a new contribution: an algebraic characterization of the relations accepted by two-way transducers when both the input and output alphabets are unary. Actually, it can be reformulated as follows: each unary two-way transducer is equivalent to a sweeping (and even rotating) transducer. We also show that the assumptions made on the size of the alphabets are required, that is, sweeping transducers weakens the 2-way transducers whenever at least one of the alphabet is non-unary. On the path, we discuss on the computational power of some algebraic operations on word relations, introduced in the aim of describing the behavior of 2-way transducers or, more generally, of 2-way weighted automata. In particular, the mirror operation, consisting in reversing the input word in order to describe a right to left scan, draws our attention. Finally, we study another kind of operations, more adapted for binary word relations: the composition. We consider the transitive closure of relations. When the relation belongs to some very restricted sub-family of rational relations, we are able to compute its transitive closure and we set its complexity. This quickly becomes uncomputable when higher classes are considered.

Cette thèse porte sur deux extensions naturelles des Automates Finis (FA) : les automates finis bidirectionnels (2FA) et les transducteurs bidirectionnels (2T). Il est bien connu que les 2FA sont calculatoirement équivalents aux FA, même dans leur version non déterministe (2NFA). Cependant, dans le domaine de la complexité descriptionnelle, certaines questions demeurent. Posée par Sakoda et Sipser en 1978, la question du coût de la simulation d'un 2NFA par 2DFA (D pour déterministe) est encore inconnue. Dans cette thèse, je traite cette question dans un cas restreint où les choix non déterministes effectués par le 2NFA ne peuvent avoir lieu qu'au bord du mot d'entrée d'entrée (2ONFA). Les transducteurs classiques (unidirectionnels) sont bien connus et jouissent de caractérisations fortes (relations rationnelles, logique). Cependant leur version bidirectionnelle (2T) est assez méconnue, spécialement dans le cas non déterministe. Dans ce domaine,ma thèse apporte une contribution nouvelle : une caractérisation algébrique des relations acceptées lorsque les alphabets d'entrée et de sortie sont unaires. Celle-ci peut s'exprimer differemment : les 2T unaires sont équivalents au 2T boustrophédons. Je montre également que les hypothèses fortes faites sur les alphabets sont nécessaires. L étude des relations sur les mots et de leur clôture transitive est un autre aspect abordé dans ma thèse
This PhD is about two natural extensions of Finite Automata (FA): the 2-way fa (2FA) and the 2-way transducers (2T). It is well known that 2FA s are computably equivalent to FAs, even in their nondeterministic (2nfa) variant. However, in the field of descriptional complexity, some questions remain. Raised by Sakoda and Sipser in 1978, the question of the cost of the simulation of 2NFA by 2DFA (the deterministic variant of 2FA) is still open. In this manuscript, we give an answer in a restricted case in which the nondeterministic choices of the simulated 2NFA may occur at the boundaries of the input tape only (2ONFA). We show that every 2ONFA can be simulated by a 2DFA of subexponential (but superpolynomial) size. Under the assumptions L=NL, this cost is reduced to the polynomial level. Moreover, we prove that the complementation and the simulation by a halting 2ONFA is polynomial. We also consider the anologous simulations for alternating devices. Providing a one-way write-only output tape to FAs leads to the notion of transducer. Contrary to the case of finite automata which are acceptor, 2-way transducers strictly extends the computational power of 1-way one, even in the case where both the input and output alphabets are unary. Though 1-way transducers enjoy nice properties and characterizations (algebraic, logical, etc. . . ), 2-way variants are less known, especially the nondeterministic case. In this area, this manuscript gives a new contribution: an algebraic characterization of the relations accepted by two-way transducers when both the input and output alphabets are unary. Actually, it can be reformulated as follows: each unary two-way transducer is equivalent to a sweeping (and even rotating) transducer. We also show that the assumptions made on the size of the alphabets are required, that is, sweeping transducers weakens the 2-way transducers whenever at least one of the alphabet is non-unary. On the path, we discuss on the computational power of some algebraic operations on word relations, introduced in the aim of describing the behavior of 2-way transducers or, more generally, of 2-way weighted automata. In particular, the mirror operation, consisting in reversing the input word in order to describe a right to left scan, draws our attention. Finally, we study another kind of operations, more adapted for binary word relations: the composition. We consider the transitive closure of relations. When the relation belongs to some very restricted sub-family of rational relations, we are able to compute its transitive closure and we set its complexity. This quickly becomes uncomputable when higher classes are considered

In Nick Cave’s weekly email letter responses to fans’ questions, he seeks to establish intimate, spiritual connections. Laid out on what resembles watermarked paper and as if they have been typed, there is a material, embodied intimacy to not only the way the letters appear, like they are scented analogue exchanges in a dematerialized digital world, but in their imagined two-wayness, as if fan and Cave are privately conversing. Topics discussed range from religion to death, love and longing, and to the taste distinctions that one might make over art, literature, music, and poetry. It is these epistolary letters that I analyse in this chapter, finding love and loneliness across their sheets.