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We study the problem of searching on data that is encrypted using a public key system. Consider user Bob who sends email to user Alice encrypted under Alice's public key. An email gateway wants to test whether the email contains the keyword " urgent " so that it could route the email accordingly. Alice, on the other hand does not wish to give the gateway(More)
We consider the following generalization of the popular \15 puzzle." Let T be a tree with n vertices and with k < n distinct pebbles numbered 1; ;k on distinct vertices. A move consists in transferring a pebble from its current position to an adjacent unoccupied vertex. We ask the following question: Is a given arrangement of pebbles reachable from another?(More)
This paper investigates the possibility of disposing of interaction between prover and verifier in a zero-knowledge proof if they share beforehand a short random string. Without any assumption, it is proven that noninteractive zero-knowledge proofs exist for some number-theoretic languages for which no efficient algorithm is known. If deciding quadratic(More)
Non-Interactive Zero Knowledge (NIZK), introduced by Blum, Feld-man, and Micali in 1988, is a fundamental cryptographic primitive which has attracted considerable attention in the last decade and has been used throughout modern cryptography in several essential ways. For example, NIZK plays a central role in building provably secure public-key cryptosystems(More)
We investigate structural properties of statistical zero knowledge (SZK) both in the interactive and in the non-interactive model. Speciically, we look into the closure properties of SZK languages under monotone logical formula composition. This gives rise to new protocol techniques. We show that interactive SZK for random self re-ducible languages (RSR)(More)
In the bare public-key model (BPK in short), each verifier is assumed to have deposited a public key in a file that is accessible by all users at all times. In this model, introduced by Canetti et al. [STOC 2000], constant-round black-box concurrent and resettable zero knowledge is possible as opposed to the standard model for zero knowledge. As pointed out(More)
We study combinatorial optimization problems involving one-parameter selfish agents considered by Archer and Tardos [FOCS 2001]. In particular, we show that, if agents can lie in one direction (that is they either overbid or underbid) then any (polynomial-time) c-approximation algorithm, for the optimization problem without selfish agents, can be turned(More)
The aim of this paper is twofold. 1) We raise concerns regarding possible violations of user privacy relative to the use of X509 Certificates and the Transport Layer Security protocol. We stress that this approach to secure network transactions, while preserving the interests of service providers, neglects to consider the right to privacy of the users. 2)(More)