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Suppose we are given a proof of knowledge P in which a prover demonstrates that he knows a solution to a given problem instance. Suppose also that we have a secret sharing scheme S on n participants. Then under certain assumptions on P and S, we show how to transform P into a witness indistinguishable protocol, in which the prover demonstrates knowledge of(More)
In this paper we present a new multi-authority secret-ballot election scheme that guarantees privacy, universal verifiability, and robustness. It is the first scheme for which the performance is optimal in the sense that time and communication complexity is minimal both for the individual voters and the authorities. An interesting property of the scheme is(More)
A publicly verifiable secret sharing (PVSS) scheme is a verifiable secret sharing scheme with the property that the validity of the shares distributed by the dealer can be verified by any party; hence verification is not limited to the respective participants receiving the shares. We present a new construction for PVSS schemes, which compared to previous(More)
We present new results in the framework of secure multi-party computation based on homomorphic threshold cryptosystems. We introduce the conditional gate as a special type of multiplication gate that can be realized in a surprisingly simple and efficient way using just standard homomorphic threshold ElGamal encryption. As addition gates are essentially for(More)
We consider the framework of secure n-party computation based on threshold homomorphic cryptosystems as put forth by Cramer, Damgård, and Nielsen at Eurocrypt 2001. When used with Paillier's cryptosystem, this framework allows for efficient secure evaluation of any arithmetic circuit defined over ZN , where N is the RSA modulus of the underlying Paillier(More)
A family of pseudorandom generators based on the decisional Diffie-Hellman assumption is proposed. The new construction is a modified and generalized version of the Dual Elliptic Curve generator proposed by Barker and Kelsey. Although the original Dual Elliptic Curve generator is shown to be insecure, the modified version is provably secure and very(More)
For the homomorphic Paillier cryptosystem we construct a protocol for secure modulo reduction, that on input of an encryption x with x of bit length x and a public 'modulus' a of bit length a outputs an encryption x mod a. As a result, a protocol for computing an encrypted integer division x div a is obtained. Surprisingly, efficiency of the protocol is(More)
The asymptotic security of the Blum-Blum-Shub (BBS) pseudo-random generator has been studied by Alexi et al. and Vazirani and Vazi-rani, who proved independently that O(log log N) bits can be extracted on each iteration, where N is the modulus (a Blum integer). The concrete security of this generator has been analyzed previously by Fischlin and Schnorr and(More)
CAFE (" Conditional Access for Europe ") is an ongoing project in the European Community's ESPRIT program. The goal of CAFE is to develop innovative systems for conditional access, and in particular, digital payment systems. An important aspect of CAFE is high security of all parties concerned, with the least possible requirements that they are forced to(More)