NTRU is an efficient patented public-key cryptosystem proposed in 1996 by Hoffstein, Pipher and Silverman. Although no devastating weakness of NTRU has been found, Jaulmes and Joux presented at Crypto ’00 a simple chosen-ciphertext attack against NTRU as originally described. This led Hoffstein and Silverman to propose three encryption padding schemes more or less based on previous work by Fuji...

Many cryptographic systems based on elliptic curves are proven secure in the Random Oracle Model, assuming there exist probabilistic functions that map elements in some domain (e.g. bitstrings) onto uniformly and independently distributed points in a curve. When implementing such systems, and in order for the proof to carry over to the implementation, those mappings must be instantiated with co...

We present a new unifying framework for constructing non-interactive threshold encryption and signature schemes, as well as broadcast encryption schemes, and in particular, derive several new cryptosystems based on hardness of factoring, including: – a threshold signature scheme (in the random oracle model) that supports ad-hoc groups (i.e., exponential number of identities and the set-up is in...

Certificateless public key cryptography (CLPKC), with properties of no key escrow and no certificate, has received a lot of attention since its invention. However, membership revocation in certificateless cryptosystem still remains a non-trivial problem: the existing solutions are not practical for use due to either a costly mediator or enormous computation (secret channel). In this paper, we p...

A deniable authentication scheme using RSA is described and proven secure in the random oracle model. A countermeasure to a well-known attack on efficient deniable authentication to multiple recipients is described and proven secure.

In this paper, we show that the AugPAKE protocol [16] provides the semantic security of session keys under the strong Diffie-Hellman (SDH) assumption in the random oracle model.

We present an implementation of the protocol of Lindell and Pinkas for secure two-party computation which is secure against malicious adversaries [13]. This is the first running system which provides security against malicious adversaries according to rigorous security definition and without using the random oracle model. We ran experiments showing that the protocol is practical. In addition we...

We assume that the convex set K is presented by an oracle. We shall consider two kinds of oracles: • Separation Oracle: we ask if a point x is in K. If x ∈ K, the oracle answers ”yes”. If x / ∈ K the oracle returns a half-space H such that K ⊂ H and x / ∈ K. In addition, we are given two numbers r,R ∈ R such that there exists a point x0 (unknown) satisfying x0 + rBn ⊂ K ⊂ RBn. • Membership Orac...

Here we propose an identity based signcryption scheme in the multi-PKG environment where sender and receiver receive public key from different PKG. We also define security models for our scheme and give security proofs in random oracle model.