Jaime Muñoz Masqué

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We propose a reduced equation for hyperelliptic curves of genus 2 over finite fields ? q of q elements with characteristic different from 2 and 5. We determine the number of isomorphism classes of genus-2 hyperelliptic curves having an ? q -rational Weierstrass point. These results have applications to hyperelliptic curve cryptography.
A secure broadcasting cryptosystem must provide a secure communication channel from a sender to a group of legal or authorized receivers. Many of the proposed systems [3-5] require a large number of broadcast messages and present a number of problems. Moreover, Liaw [2] proposed a secure broadcasting scheme with fewer broadcasting messages, which allows(More)
Multisignature schemes are digital signature schemes that permit one to determine a unique signature for a given message, depending on the signatures of all the members of a specific group. In this work, we present a new semi-short multisignature scheme based on the Subgroup Discrete Logarithm Problem (SDLP) and on the Integer Factorization Problem (IFP).(More)
Vaudenay’s cryptanalysis to Chor-Rivest cryptosystem is not applicable if the parameters p and h of the finite field are both prime integers. This case is analyzed below and the parameters for which such cryptosystem is cryptographically interesting are listed. Regrettably the resulting cryptosystems are not very efficient in practice.