Ed Dawson

Twisted Edwards Curves Revisited

This paper introduces fast algorithms for performing group operations on twisted Edwards curves, pushing the recent speed limits of Elliptic Curve Cryptography (ECC) forward in a wide range of applications. Notably, the new addition algorithm uses

Providing Receipt-Freeness In Mixnet-Based Voting Protocols

8\mathrm{\textbf{M}}

Heuristic design of cryptographically strong balanced Boolean functions

for suitably selected curve constants. In comparison, the fastest point addition algorithms for (twisted) Edwards curves stated in the literature use

A computer package for measuring the strength of encryption algorithms

9\mathrm{\textbf{M}} + 1\mathrm{\textbf{S}}

The LILI-II Keystream Generator

. It is also shown that the new addition algorithm can be implemented with four processors dropping the effective cost to

Bit-Pattern Based Integral Attack

2\mathrm{\textbf{M}}

Design and cryptanalysis of transform-based analog speech scramblers

. This implies an effective speed increase by the full factor of 4 over the sequential case. Our results allow faster implementation of elliptic curve scalar multiplication. In addition, the new point addition algorithm can be used to provide a natural protection from side channel attacks based on simple power analysis (SPA).

Evolutionary Heuristics for Finding Cryptographically Strong S-Boxes

It had been thought that it is difficult to provide receipt-freeness in mixnet-based electronic voting schemes. Any kind of user chosen randomness can be used to construct a receipt, since a user can prove to a buyer how he had encrypted the ballot. In this paper we propose a simple and efficient method to incorporate receipt-freeness in mixnet-based electronic voting schemes by using the well known re-encryption technique and designated verifier re-encryption proof (DVRP). In our scheme a voter has to prepare his encrypted ballot through a randomization service provided by a tamper resistant randomizer (TRR), in such a way that he finally loses his knowledge on randomness. This method can be used in most mixnet-based electronic voting scheme to provide receipt-freeness.

Dragon: a fast word based stream cipher

Advances in the design of Boolean functions using heuristic techniques are reported. A genetic algorithm capable of generating highly nonlinear balanced Boolean functions is presented. Hill climbing techniques are adapted to locate balanced, highly nonlinear Boolean functions that also almost satisfy correlation immunity. The definitions for some cryptographic properties are generalised, providing a measure suitable for use as a fitness function in a genetic algorithm seeking balanced Boolean functions that satisfy both correlation immunity and the strict avalanche criterion. Results are presented demonstrating the effectiveness of the methods.

LILI Keystream Generator

Designers and users of encryption algorithms used in cipher systems need a systematic approach in examining their ciphers prior to use, to ensure that they are safe from cryptanalytic attack. This paper describes a computer package used for assessing the security of newly-developed encryption algorithms.