In MIST 2012 conference Singh et al [21] presented lattice based forward-secure identity based encryption schemes based on LWE assumption in the random oracle model as well as in the standard model. In this paper we propose lattice based forward-secure identity based encryption scheme with shorter ciphertext in the random oracle model. We have reduced size of the ciphertext C from (m(i+ 2)+ 1)×...

In a digital signature scheme with message recovery, rather than transmitting the message m and its signature σ, a single enhanced signature τ is transmitted. The verifier is able to recover m from τ and at the same time verify its authenticity. The two most important parameters of such a scheme are its security and overhead |τ | − |m|. A simple argument shows that for any scheme with “n bits s...

At PKC 2006, Yang, Wong, Deng and Wang proposed the notion of anonymous signature schemes where signatures do not reveal the signer’s identity, as long as some parts of the message are unknown. They also show how to modify the RSA scheme and the Schnorr scheme to derive anonymous signatures in the random oracle model. Here we present a general and yet very efficient approach to build such anony...

Ensemble methods with Random Oracles have been proposed recently (Kuncheva and Rodŕıguez, 2007). A random-oracle classifier consists of a pair of classifiers and a fixed, randomly created oracle that selects between them. Ensembles of random-oracle decision trees were shown to fare better than standard ensembles. In that study, the oracle for a given tree was a random hyperplane at the root of ...

The indistinguishability security of a public-key cryptosystem can be reduced to a computational hard assumption in the random oracle model, where the solution to a computational hard problem is hidden in one of the adversary’s queries to the random oracle. Usually, there is a finding loss in finding the correct solution from the query set, especially when the decisional variant of the computat...

The Random Oracle Model and the Ideal Cipher Model are two of the most popular idealized models in cryptography. It is a fundamentally important practical and theoretical problem to compare the relative strengths of these models and to see how they relate to each other. Recently, Coron et al. [8] proved that one can securely instantiate a random oracle in the ideal cipher model. In this paper, ...

It has been roughly two decades since the random oracle model for security reductions was introduced and one decade since we first discussed the controversy that had arisen concerning its use. In this retrospective we argue that there is no evidence that the need for the random oracle assumption in a proof indicates the presence of a realworld security weakness in the corresponding protocol. We...

The Full-Domain Hash (FDH) signature scheme [3] forms one the most basic usages of random oracles. It works with a family F of trapdoor permutations (TDP), where the signature of m is computed as f−1(h(m)) (here f ∈R F and h is modelled as a random oracle). It is known to be existentially unforgeable for any TDP family F [3], although a much tighter security reduction is known for a restrictive...

Partially blind signature schemes are the most important ingredient for anonymity in off-line e-cash system. In this paper, a new approach to setup formal security arguments in random oracle model for factorization based partially blind signature schemes is presented. Then a provably secure and efficient scheme based on quadratic residue is proposed. The approach also allows one to give formal ...

Optimal Asymmetric Encryption Padding (OAEP) is a technique for converting the RSA trapdoor permutation into a chosen ciphertext secure system in the random oracle model. OAEP padding can be viewed as two rounds of a Feistel network. We show that for the Rabin and RSA trapdoor functions a much simpler padding scheme is sufficient for chosen ciphertext security in the random oracle model. We sho...