CryptoDB

Omer Reingold

Publications

Year
Venue
Title
2019
TCC
2018
JOFC
2015
ASIACRYPT
2014
JOFC
2012
EUROCRYPT
2010
EUROCRYPT
2010
EPRINT
This paper revisits the construction of Universally One-Way Hash Functions (UOWHFs) from any one-way function due to Rompel (STOC 1990). We give a simpler construction of UOWHFs which also obtains better efficiency and security. The construction exploits a strong connection to the recently introduced notion of *inaccessible entropy* (Haitner et al. STOC 2009). With this perspective, we observe that a small tweak of any one-way function f is already a weak form of a UOWHF: Consider F(x, i) that outputs the i-bit long prefix of f(x). If F were a UOWHF then given a random x and i it would be hard to come up with x' \neq x such that F(x, i) = F(x', i). While this may not be the case, we show (rather easily) that it is hard to sample x' with almost full entropy among all the possible such values of x'. The rest of our construction simply amplifies and exploits this basic property. With this and other recent works we have that the constructions of three fundamental cryptographic primitives (Pseudorandom Generators, Statistically Hiding Commitments and UOWHFs) out of one-way functions are to a large extent unified. In particular, all three constructions rely on and manipulate computational notions of entropy in similar ways. Pseudorandom Generators rely on the well-established notion of pseudoentropy, whereas Statistically Hiding Commitments and UOWHFs rely on the newer notion of inaccessible entropy.
2009
CRYPTO
2007
EPRINT
We study the round complexity of various cryptographic protocols. Our main result is a tight lower bound on the round complexity of any fully-black-box construction of a statistically-hiding commitment scheme from one-way permutations, and even from trapdoor permutations. This lower bound matches the round complexity of the statistically-hiding commitment scheme due to Naor, Ostrovsky, Venkatesan and Yung (CRYPTO '92). As a corollary, we derive similar tight lower bounds for several other cryptographic protocols, such as single-server private information retrieval, interactive hashing, and oblivious transfer that guarantees statistical security for one of the parties. Our techniques extend the collision-finding oracle due to Simon (EUROCRYPT '98) to the setting of interactive protocols (our extension also implies an alternative proof for the main property of the original oracle). In addition, we substantially extend the reconstruction paradigm of Gennaro and Trevisan (FOCS '00). In both cases, our extensions are quite delicate and may be found useful in proving additional black-box separation results.
2006
CRYPTO
2006
JOFC
2006
EPRINT
We give a construction of statistically-hiding commitment schemes (ones where the hiding property holds information theoretically), based on the minimal cryptographic assumption that one-way functions exist. Our construction employs two-phase commitment schemes, recently constructed by Nguyen, Ong and Vadhan (FOCS 06), and universal one-way hash functions introduced and constructed by Naor and Yung (STOC 89) and Rompel (STOC `90).
2005
EUROCRYPT
2005
TCC
2004
EUROCRYPT
2004
TCC
2002
JOFC
2001
EUROCRYPT
2001
EPRINT
Factoring integers is the most established problem on which cryptographic primitives are based. This work presents an efficient construction of {\em pseudorandom functions} whose security is based on the intractability of factoring. In particular, we are able to construct efficient length-preserving pseudorandom functions where each evaluation requires only a {\em constant} number of modular multiplications per output bit. This is substantially more efficient than any previous construction of pseudorandom functions based on factoring, and matches (up to a constant factor) the efficiency of the best known factoring-based {\em pseudorandom bit generators}.
2000
EPRINT
We show how to construct pseudo-random permutations that satisfy a certain cycle restriction, for example that the permutation be cyclic (consisting of one cycle containing all the elements) or an involution (a self-inverse permutation) with no fixed points. The construction can be based on any (unrestricted) pseudo-random permutation. The resulting permutations are defined succinctly and their evaluation at a given point is efficient. Furthermore, they enjoy a {\em fast forward} property, i.e. it is possible to iterate them at a very small cost.
1999
EUROCRYPT
1999
JOFC
1998
CRYPTO
1997
EPRINT
The Diffie-Hellman key-exchange protocol may naturally be extended to k>2 parties. This gives rise to the generalized Diffie-Hellman assumption (GDH-Assumption). Naor and Reingold have recently shown an efficient construction of pseudo-random functions and reduced the security of their construction to the GDH-Assumption. In this note, we prove that breaking this assumption modulo a composite would imply an efficient algorithm for factorization. Therefore, the security of both the key-exchange protocol and the pseudo-random functions can be reduced to factoring.
1996
EPRINT
Luby and Rackoff showed a method for constructing a pseudo-random permutation from a pseudo-random function. The method is based on composing four (or three for weakened security) so called Feistel permutations each of which requires the evaluation of a pseudo-random function. We reduce somewhat the complexity of the construction and simplify its proof of security by showing that two Feistel permutations are sufficient together with initial and final pair-wise independent permutations. The revised construction and proof provide a framework in which similar constructions may be brought up and their security can be easily proved. We demonstrate this by presenting some additional adjustments of the construction that achieve the following: 1. Reduce the success probability of the adversary. 2. Provide a construction of pseudo-random permutations with large input size using pseudo-random functions with small input size. 3. Provide a construction of a pseudo-random permutation using a single pseudo-random function.

Program Committees

TCC 2009 (Program chair)
Crypto 2007
TCC 2007
Eurocrypt 2004
TCC 2004
Crypto 2001