In this paper, we propose a new method for designing public key cryptosystems based on general non-commutative rings. The key idea of our proposal is that for a given non-commutative ring, we can define polynomials and take them as the underlying work structure. By doing so, it is easy to implement Diffie-Helman-like key exchange protocol. And consequently, ElGamal-like cryptosystems can be der...

This report presents a brief survey on secret key and public key cryptography algorithms. These include: block ciphers, stream ciphers, RSA, ElGamal and Elliptic Curve Cryptosystems (ECC). Since ECC achieved security levels comparable to those of traditional public key cryptosystems using smaller keys (160 bits), this work focus more on ECC. Finally, this work also presents a survey on scalar m...

This article presents a new signcryption scheme which is based on the Schnorr digital signature algorithm. The new scheme represents my personal contribution to signcryption area. I have been implemented the algorithm in a program and here are provided the steps of the algorithm, the results and some examples. The paper also contains the presentation of the original Signcryption scheme, based o...

p ) , only the legitimate signer with knowledge of x can generate the signatures to satisfy the verification. Although the attacker can generate bogus signatures in the signature collection protocol, these signatures cannot satisfy the batch verification criterion. There are some other secure ElGamal type signature schemes as proposed in [4] that can also be used to design similar DSA type secu...

In this paper, we propose two new anonymous secure electronic voting schemes that protect the privacy of the voters and prevent double voting. These schemes do not require any special voting channel and the communications can occur entirely over existing networks such as the Internet. The proposed schemes are based on ElGamal digital signature algorithm and can be applied to elections in a vari...

The public key cryptosystems MST1 and MST2 make use of certain kinds of factorizations of finite groups. We show that generalizing such factorizations to infinite groups allows a uniform description of several proposed cryptographic primitives. In particular, a generalization of MST2 can be regarded as a unifying framework for several suggested cryptosystems including the ElGamal public key sys...

In a threshold broadcast encryption scheme, a sender chooses (ad-hoc) a set of n receivers and a threshold t, and then encrypts a message by using the public keys of all the receivers, in such a way that the original plaintext can be recovered only if at least t receivers cooperate. This kind of scheme has many applications in mobile ad-hoc networks, characterized by their lack of infrastructur...

We consider the cryptographic group of Signed Quadratic Residues. This group is particularly useful for cryptography since it is a “gap-group,” in which the computational problem (i.e., computing square roots) is as hard as factoring, while the corresponding decisional problem (i.e., recognizing signed quadratic residues) is easy. We are able to show that under the factoring assumption, the Str...

We define a new type of mix network that offers a reduced form of robustness: the mixnet can prove that every message it outputs corresponds to an input submitted by a player without revealing which input (for honest players). We call mixnets with this property reputable mixnets. Reputable mixnets are not fully robust, because they offer no guarantee that distinct outputs correspond to distinct...

We exhibit eecient threshold cryptosystems which are secure against adaptive adversaries even when the players cannot erase their local data. Speciically, we present erasure-free adaptively-secure protocols for distributed decryption in Cramer-Shoup cryptosystem. Our techniques are also applicable for distributing the secret-key operation of other cryptosystems, like RSA, DSS, and ElGamal, as w...