. We present a new method to forge ElGamal signatures if the public parameters of the system are not chosen properly. Since the secret key is hereby not found this attack shows that forging ElGamal signatures is sometimes easier than the underlying discrete logarithm problem. 1 Introduction ElGamal's digital signature scheme [4] relies on the difficulty of computing discrete logarithms in the multiplicative group IF p and can therefore be broken if the computation of discrete logarithms is feasible. However, the converse has never been proved. In this paper we show that it is sometimes possible to forge signatures without breaking the underlying discrete logarithm problem. This shows that the ElGamal signature scheme and some variants of the scheme must be used very carefully. The paper is organized as follows. Section 2 describes the ElGamal signature scheme. In Section 3 we present a method to forge signatures if some additional information on the generator is known. We show that...

In this paper we propose a secure protocol for authenticated key agreement based on Diffie-Hellman key agreement, which works in an elliptic curve group. We also present a simpler authenticated key agreement protocol than the proposed one and a multiple key agreement protocol which enables the participants to share two or more keys in one execution of the protocol. We prove that our protocols meet the security attributes under the assumption that the elliptic curve discrete logarithm problem is secure. Key Words: Protocols, authenticated key agreement, elliptic curves. 1.

In this paper we propose an authenticated key agreement, which works in a braid group. We prove that our protocol meet the security attributes under the assumption that the Conjugacy Search Problem (CSP) is hard in braid group.

. We present a new method to forge ElGamal signatures if the public parameters of the system are not chosen properly. Since the secret key is hereby not found this attack shows that forging ElGamal signatures is sometimes easier than the underlying discrete logarithm problem. 1 Introduction ElGamal's digital signature scheme [4] relies on the difficulty of computing discrete logarithms in the multiplicative group IF p and can therefore be broken if the computation of discrete logarithms is feasible. However, the converse has never been proved. In this paper we show that it is sometimes possible to forge signatures without breaking the underlying discrete logarithm problem. This shows that the ElGamal signature scheme and some variants of the scheme must be used very carefully. The paper is organized as follows. Section 2 describes the ElGamal signature scheme. In Section 3 we present a method to forge signatures if some additional information on the generator is known. We show ...

Abstract — In this paper, we presented a model of privileged channel e-mailing system for Internet communication. It is the model of a real-life secure mailing system for any organization. In this model a sender can send a secret message even to a unacquainted person in an anonymous way. The users of this model are assumed to be may or may not be the members of a closed organization.

In this paper, we presented a model of e-correspondence with error correction for Internet communication. It is the model of a real-life secure e-correspondence system for any organization. In this model a sender can send a secret message even to a unacquainted person in an anonymous way. The users of this model are assumed to be may or may not be the members of a closed organization.

In this paper we show a model of an anonymous cum idiosyncratic Machiavellian mailing system for Internet communication. It is the model of a real-life secure mailing system for any organization. In this model a sender can send a secret message even to a unacquainted person in an anonymous way, later which will become idiosyncratic. The users of this model are assumed to be may or may not be the members of a closed organization.