State Transition Analysis of GSM Encryption Algorithm A5/1

A5/1 stream cipher is used in Global System for Mobile Communication(GSM) phones for secure communication. A5/1 encrypts the message transferred from a mobile user. In this paper, we present the implementation of cryptanalytic on A5/1 techniques such as minimized state recovery for recovering the session key. The number of state transitions/updations needed for a state S to reoccur is maintained in the lookup table. This table can be used to recover the initial state from which the keystream was produced. Experiments are carried out for reduced version, full A5/1 cipher on 3.20 GHz machine, and cluster computing facility

Proxy Signature Scheme with Effective Revocation Using Bilinear Pairings

We present a proxy signature scheme using bilinear pairings that provides effective proxy revocation. The scheme uses a binding-blinding technique to avoid secure channel requirements in the key issuance stage. With this technique, the signer receives a partial private key from a trusted authority and unblinds it to get his private key, in turn, overcomes the key escrow problem which is a constraint in most of the pairing-based proxy signature schemes. The scheme fulfills the necessary security requirements of proxy signature and resists other possible threats

Two-Party Threshold Key Agreement Protocol for MANETs using Pairings

In MANET environment, the nodes are mobile i.e., nodes move in and out dynamically. This causes difficulty in maintaining a central trusted authority say Certification Authority CA or Key Generation Centre KCG. In addition most of cryptographic techniques need a key to be shared between the two communicating entities. So to introduce security in MANET environment, there is a basic need of sharing a key between the two communicating entities without the use of central trusted authority. So we present a decentralized two-party key agreement protocol using pairings and threshold cryptography ideas. Our model is based on Joux2019;s three-party key agreement protocol which does not authenticate the users and hence is vulnerable to man-in-the-middle attack. This model protects from man-in-the-middle attack using threshold cryptography

Random generation of Boolean functions with high degree of correlation immunity, Journal of Telecommunications and Information Technology, 2006, nr 3

In recent years a cryptographic community is paying a lot of attention to the constructions of so called resilient functions for use mainly in stream cipher systems. Very little work however has been devoted to random generation of such functions. This paper tries to fill that gap and presents an algorithm that can generate at random highly nonlinear resilient functions. Generated functions are analyzed and compared to the results obtained from the best know constructions and some upper bounds on nonlinearity and resiliency. It is shown that randomly generated functions achieve in most cases results equal to the best known designs, while in other cases fall just behind such constructs. It is argued that the algorithm can perhaps be used to prove the existence of some resilient functions for which no mathematical prove has been given so far

Making Code Voting Secure against Insider Threats using Unconditionally Secure MIX Schemes and Human PSMT Protocols

Code voting was introduced by Chaum as a solution for using a possibly infected-by-malware device to cast a vote in an electronic voting application. Chaum's work on code voting assumed voting codes are physically delivered to voters using the mail system, implicitly requiring to trust the mail system. This is not necessarily a valid assumption to make - especially if the mail system cannot be trusted. When conspiring with the recipient of the cast ballots, privacy is broken. It is clear to the public that when it comes to privacy, computers and "secure" communication over the Internet cannot fully be trusted. This emphasizes the importance of using: (1) Unconditional security for secure network communication. (2) Reduce reliance on untrusted computers. In this paper we explore how to remove the mail system trust assumption in code voting. We use PSMT protocols (SCN 2012) where with the help of visual aids, humans can carry out $\mod 10$ addition correctly with a 99\% degree of accuracy. We introduce an unconditionally secure MIX based on the combinatorics of set systems. Given that end users of our proposed voting scheme construction are humans we \emph{cannot use} classical Secure Multi Party Computation protocols. Our solutions are for both single and multi-seat elections achieving: \begin{enumerate}[i)] \item An anonymous and perfectly secure communication network secure against a $t$-bounded passive adversary used to deliver voting, \item The end step of the protocol can be handled by a human to evade the threat of malware. \end{enumerate} We do not focus on active adversaries

Lattice-Based proof of a shuffle

In this paper we present the first fully post-quantum proof of a shuffle for RLWE encryption schemes. Shuffles are commonly used to construct mixing networks (mix-nets), a key element to ensure anonymity in many applications such as electronic voting systems. They should preserve anonymity even against an attack using quantum computers in order to guarantee long-term privacy. The proof presented in this paper is built over RLWE commitments which are perfectly binding and computationally hiding under the RLWE assumption, thus achieving security in a post-quantum scenario. Furthermore we provide a new definition for a secure mixing node (mix-node) and prove that our construction satisfies this definition.Peer ReviewedPostprint (author's final draft

Simple and Efficient Single Round Almost Perfectly Secure Message Transmission Tolerating Generalized Adversary

Patra et al. gave a necessary and sufficient condition for the possibility of almost perfectly secure message transmission protocols tolerating general, non-threshold Q^2 adversary structure. However, their protocol requires at least three rounds and performs exponential (exponential in the size of the adversary structure) computation and communication. Moreover, they have left it as an open problem to design efficient protocol for almost perfectly secure message transmission, tolerating Q^2 adversary structure. In this paper, we show the first single round almost perfectly secure message transmission protocol tolerating Q^2 adversary structure. The computation and communication complexities of the protocol are both polynomial} in the size of underlying linear secret sharing scheme (LSSS) and adversary structure. This solves the open problem raised by Patra et al.. When we restrict our general protocol to threshold adversary with n=2t+1, we obtain a single round, communication optimal almost secure message transmission protocol tolerating threshold adversary, which is much more computationally efficient and relatively simpler than the previous communication optimal protocol of Srinathan et al

A Discrete Particle Swarm Optimizer for the Design of Cryptographic Boolean Functions

A Particle Swarm Optimizer for the search of balanced Boolean functions with good cryptographic properties is proposed in this paper. The algorithm is a modified version of the permutation PSO by Hu, Eberhart and Shi which preserves the Hamming weight of the particles positions, coupled with the Hill Climbing method devised by Millan, Clark and Dawson to improve the nonlinearity and deviation from correlation immunity of Boolean functions. The parameters for the PSO velocity equation are tuned by means of two meta-optimization techniques, namely Local Unimodal Sampling (LUS) and Continuous Genetic Algorithms (CGA), finding that CGA produces better results. Using the CGA-evolved parameters, the PSO algorithm is then run on the spaces of Boolean functions from $n=7$ to $n=12$ variables. The results of the experiments are reported, observing that this new PSO algorithm generates Boolean functions featuring similar or better combinations of nonlinearity, correlation immunity and propagation criterion with respect to the ones obtained by other optimization methods