We introduce the notion of Resettable Zero-Knowledge (rZK),
a new security measure for cryptographic protocols
which strengthens the classical notion of zero-knowledge.
In essence, an rZK protocol is one that remains zero knowledge
even if an adeversary can interact with the prover many times, each
time ... more >>>

We present several new and fairly practical public-key encryption
schemes and prove them secure against
adaptive chosen ciphertext attack. One scheme is based on Paillier's
Decision Composite Residuosity (DCR) assumption,
while another is based in the classical Quadratic Residuosity (QR)
assumption. The analysis is in the standard ... more >>>

In this tutorial, selected topics of cryptology and of
computational complexity theory are presented. We give a brief overview
of the history and the foundations of classical cryptography, and then
move on to modern public-key cryptography. Particular attention is
paid to cryptographic protocols and the problem of constructing ... more >>>

In this paper, firstly we propose two new concepts concerning the notion of key escrow encryption schemes: provable partiality and independency. Roughly speaking we say that a scheme has provable partiality if existing polynomial time algorithm for recovering the secret knowing escrowed information implies a polynomial time algorithm that can ... more >>>

In this paper we compare hardness of two well known problems: the Diffie-Hellman problem and the root finding problem. We prove that in any cyclic group computing Diffie-Hellman is not weaker than root finding if certain circumstances are met. As will be discussed in the paper this theorem can affect ... more >>>

Injective one-way trapdoor functions are one of the most fundamental cryptographic primitives. In this work we give a novel construction of injective trapdoor functions based on oblivious transfer for long strings.

Our main result is to show that any 2-message statistically sender-private semi-honest oblivious transfer (OT) for ... more >>>

This work considers locally decodable codes in the computationally bounded channel model. The computationally bounded channel model, introduced by Lipton in 1994, views the channel as an adversary which is restricted to polynomial-time computation. Assuming the existence of IND-CPA secure public-key encryption, we present a construction of public-key locally decodable ... more >>>