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- Maria Isabel Gonzalez Vasco, Rainer Steinwandt
- Applicable Algebra in Engineering, Communication…
- 2003

Wagner and Magyarik outlined a conceptual public key cryptosystem based on the hardness of the word problem for finitely presented groups. At the same time, they gave a specific example of such a system. We prove that in the present form their approach is vulnerable to so-called reaction attacks. In particular, for the proposed instance it is possible to… (More)

A protocol compiler is described, that transforms any prov-ably secure authenticated 2-party key establishment into a provably secure authenticated group key establishment with 2 more rounds of communication. The compiler introduces neither idealizing assumptions nor high-entropy secrets, e. g., for signing. In particular, applying the compiler to a… (More)

- Maria Isabel Gonzalez Vasco, Mats Näslund, Igor E. Shparlinski
- Public Key Cryptography
- 2004

We generalize and extend results obtained by Boneh and Venkatesan in 1996 and by González Vasco and Shparlinski in 2000 on the hardness of computing bits of the Diffie-Hellman key, given the public values. Specifically, while these results could only exclude (essentially) error-free predictions, we here exclude any non-negligible advantage , though for… (More)

- Maria Isabel Gonzalez Vasco, Angel L. Pérez del Pozo, Pedro Taborda Duarte
- IACR Cryptology ePrint Archive
- 2009

In this paper we describe a cryptanalysis of a key exchange scheme recently proposed by´Alvarez, Tortosa, Vicent and Zamora. The scheme is based on exponentiation of block matrices over a finite field of prime order. We present an efficient reduction of the problem of disclosing the shared key to the discrete logarithm problem (DLP) in an extension of the… (More)

- Maria Isabel Gonzalez Vasco, Somayeh Heidarvand, Jorge Luis Villar
- 2010 International Conference on Security and…
- 2010

In traditional e-cash systems, the tradeoff between anonymity and fraud-detection is solved by hiding the identity of the user into the e-coin, and providing an additional triggering mechanism that opens this identity in case of double spending. Hence, fraud detection implies loss of anonymity. This seems to be a somewhat natural solution when universality… (More)

- Jens-Matthias Bohli, Maria Isabel Gonzalez Vasco, Rainer Steinwandt
- International Journal of Information Security
- 2005

We examine the popular proof models for group key establishment of Bresson et al. (LNCS 2248: 290–309, 2001; Proceedings of the 8th ACM conference on computer and communications security (CCS-8), 2001) and point out missing security properties addressing malicious protocol participants. We show that established group key establishment schemes from CRYPTO… (More)

- Maria Isabel Gonzalez Vasco, Igor E. Shparlinski
- Electronic Colloquium on Computational Complexity
- 2000

Boneh and Venkatesan have recently proposed a polynomial time algorithm for recovering a " hidden " element α of a finite field IFp of p elements from rather short strings of the most significant bits of the remainder modulo p of αt for several values of t selected uniformly at random from IF * p. We use some recent bounds of exponential sums to generalize… (More)

- Maria Isabel Gonzalez Vasco, Igor E. Shparlinski
- Electronic Colloquium on Computational Complexity
- 2000

Boneh and Venkatesan have recently proposed a polynomial time algorithm for recovering a " hidden " element α of a finite field Fp of p elements from rather short strings of the most significant bits of the remainder modulo p of αt for several values of t selected uniformly at random from F * p. Unfortunately the applications to the computational security… (More)

- Jens-Matthias Bohli, Maria Isabel Gonzalez Vasco, Rainer Steinwandt
- IACR Cryptology ePrint Archive
- 2006

A provably secure password-authenticated protocol for group key establishment in the common reference string (CRS) model is presented. Our construction assumes the participating users to share a common password and combines smooth hashing as introduced by Cramer and Shoup with a construction of Burmester and Desmedt. Our protocol is constant-round. Namely,… (More)

- Maria Isabel Gonzalez Vasco, Martin Rötteler, Rainer Steinwandt
- Experimental Mathematics
- 2003