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The precise nature of the pathogen having caused early plague pandemics is uncertain. Although Yersinia pestis is a likely candidate for all three plague pandemics, the very rare direct evidence that can be deduced from ancient DNA (aDNA) analysis is controversial. Moreover, which of the three biovars, Antiqua, Medievalis or Orientalis, was associated with these pandemics is still debated. There is a need for phylogenetic analysis performed on Y. pestis strains isolated from countries from which plague probably arose and is still endemic. In addition there exist technical difficulties inherent to aDNA investigations and a lack of appropriate genetic targets. The recently described CRISPRs (clustered regularly interspaced short palindromic repeats) may represent such a target. CRISPR loci consist of a succession of highly conserved regions separated by specific "spacers" usually of viral origin. To be of use, data describing the mechanisms of evolution and diversity of CRISPRs in Y. pestis, its closest neighbors, and other species which might contaminate ancient DNA, are necessary. [ABSTRACT FROM AUTHOR]

Heterogeneous non-functional requirements of Distributed Real-Time Embedded (DRE) system put a limit on middleware engineering: the middleware must reflect application requirements, with limited runtime impact. Thus, building an application-tailored middleware is both a requirement and a challenge. In this paper, we provide an overview of our work on the construction of middleware. We focus on two complementary projects: the definition of middleware that provides strong support for both tailorability and verification of its internals; the definition of a methodology that enables the automatizing of key steps of middleware construction. We illustrate how our current work on PolyORB, Ocarina and the use of Petri Nets allows designer to build the middleware that precisely matches its application requirements and comes with precise proof of its properties. [ABSTRACT FROM AUTHOR]

The concept of universal designated verifier signatures was introduced by Steinfeld, Bull, Wang and Pieprzyk at Asiacrypt 2003. We propose two new efficient constructions for pairing-based short signatures. The first scheme is based on Boneh-Boyen signatures and, its security can be analyzed in the standard security model. We reduce its resistance to forgery to the hardness of the strong Diffie-Hellman problem, under the knowledge-of-exponent assumption. The second scheme is compatible with the Boneh-Lynn-Shacham signatures and is proven unforgeable, in the random oracle model, under the assumption that the computational bilinear Diffie-Hellman problem is untractable. Both schemes are designed for devices with constrained computation capabilities since the signing and the designation procedure are pairing-free. [ABSTRACT FROM AUTHOR]

We introduce a new undeniable signature scheme which is existentially unforgeable and anonymous under chosen message attacks in the standard model. The scheme is an embedding of Boneh and Boyen's recent short signature scheme in a group where the decisional Diffie-Hellman problem is assumed to be difficult. The anonymity of our scheme relies on a decisional variant of the strong Diffie-Hellman assumption, while its unforgeability relies on the strong Diffie-Hellman assumption. [ABSTRACT FROM AUTHOR]

Many variants of Chaum and van Antwerpen's undeniable signatures have been proposed to achieve specific properties desired in real-world applications of cryptography. Among them, directed signatures were introduced by Lim and Lee in 1993. Directed signatures differ from the well-known confirmer signatures in that the signer has the simultaneous abilities to confirm, deny and individually convert a signature. The universal conversion of these signatures has remained an open problem since their introduction in 1993. This paper provides a positive answer to this quest by showing a very efficient design for universally convertible directed signatures (UCDS) both in terms of computational complexity and signature size. Our construction relies on the so-called xyz-trick applicable to bilinear map groups. We define proper security notions for UCDS schemes and show that our construction is secure in the random oracle model, under computational assumptions close to the CDH and DDH assumptions. Finally, we introduce and realize traceable universally convertible directed signatures where a master tracing key allows to link signatures to their direction. [ABSTRACT FROM AUTHOR]

We provide evidence that the unforgeability of several discrete-log based signatures like Schnorr signatures cannot be equivalent to the discrete log problem in the standard model. This contradicts in nature well-known proofs standing in weakened proof methodologies, in particular proofs employing various formulations of the Forking Lemma in the random oracle Model. Our impossibility proofs apply to many discrete-log-based signatures like ElGamal signatures and their extensions, DSA, ECDSA and KCDSA as well as standard generalizations of these, and even RSA-based signatures like GQ. We stress that our work sheds more light on the provable (in)security of popular signature schemes but does not explicitly lead to actual attacks on these. [ABSTRACT FROM AUTHOR]

Undeniable signatures were introduced in 1989 by Chaum and van Antwerpen to limit the self-authenticating property of digital signatures. An extended concept - the convertible undeniable signatures - proposed by Boyar, Chaum, Damgård and Pedersen in 1991, allows the signer to convert undeniable signatures to ordinary digital signatures. We present a new efficient convertible undeniable signature scheme based on bilinear maps. Its unforgeability is tightly related, in the random oracle model, to the computational Diffie-Hellman problem and its anonymity to a non-standard decisional assumption. The advantages of our scheme are the short length of the signatures, the low computational cost of the signature and the receipt generation. Moreover, a variant of our scheme permits the signer to universally convert signatures pertaining only to a specific time period. We formalize this notion as the time-selective conversion. Keywords: Convertible undeniable signatures, bilinear maps, anonymity, exact security, time-selective conversion. [ABSTRACT FROM AUTHOR]

The concept of Designated Verifier Signatures (DVS) was introduced by Jakobsson, Sako and Impagliazzo at Eurocrypt'96. These signatures are intended to a specific verifier, who is the only one able to check their validity. In this context, we formalize the notion of privacy of signer's identity which captures the strong designated verifier property investigated in their paper. We propose a variant of the pairing-based DVS scheme introduced at Asiacrypt'03 by Steinfeld, Bull, Wang and Pieprzyk. Contrary to their proposal, our new scheme can be used with any admissible bilinear map, especially with the low cost pairings and achieves the new anonymity property (in the random oracle model). Moreover, the unforgeability is tightly related to the Gap-Bilinear Diffie-Hellman assumption, in the random oracle model and the signature length is around 75% smaller than the original proposal. Keywords: Designated verifier signatures, Privacy of signer's identity, Bilinear Diffie-Hellman problems, Exact security, Tight reduction [ABSTRACT FROM AUTHOR]

Biasing techniques in TRIPOLI-2 are found upon two principles a continuous importance is assigned to each phase space point as a factorized function of space, energy and direction ; the simulation is carried out such as the particle weight remains in accordance with the assigned weight, and uses a biased total cross section which is supposed constant between two collisions. The particle track is sampled with an adapted exponential transform and the collision is biased in taking into account voids if it is necessary. These biasing techniques allow to study many different problems and are used for many years. [ABSTRACT FROM AUTHOR]