Differential Collision Attack on Reduced FOX Block Cipher

This paper presents a method for differen- tial collision attack of reduced FOX block cipher based on 4-round distinguishing property. It can be used to attack 5, 6 and 7-round FOX64 and 5-round FOX128. Our attack has a precomputation phase, but it can be obtained before attack and computed once for all. This attack on the reduced to 4-round FOX64 requires only 7 chosen plaintexts, and performs 242.8 4-round FOX64 encryptions. It could be extended to 5 （6, 7）-round FOX64 by a key exhaustive search behind the fourth round.

Cryptanalysis of Cryptosystems Based on General Linear Group

Advances in quantum computers threaten to break public key cryptosystems such as RSA, ECC, and EIGamal on the hardness of factoring or taking a discrete logarithm, while no quantum algorithms are found to solve certain mathematical problems on non-commutative algebraic structures until now. In this background, Majid Khan et al.proposed two novel public-key encryption schemes based on large abelian subgroup of general linear group over a residue ring. In this paper we show that the two schemes are not secure. We present that they are vulnerable to a structural attack and that, it only requires polynomial time complexity to retrieve the message from associated public keys respectively. Then we conduct a detailed analysis on attack methods and show corresponding algorithmic description and efficiency analysis respectively. After that, we propose an improvement assisted to enhance Majid Khan's scheme. In addition, we discuss possible lines of future work.

Cryptanalysis of Threshold-proxy Threshold-signature Schemes

Recently,Hwang et al.proposed a （t,n） threshold-proxy （c,m） thresholdsignature schemes,in which only any t or more original signers of n original signers can authorize a proxy group of m proxy signers and then only c or more proxy signers can cooperatively generate threshold-proxy threshold-signature.In this scheme,they claimed that original signers cannot forge the proxy signature and the proxy signers cannot forge signature on behalf of the original signers.However,in this paper,we will give a attack to show that their scheme can not resist impersonation attacks.

Cryptanalysis of a Cryptosystem with Non- Commutative Platform Groups

A cryptosystem with non-commutative platform groups based on conjugator search problem was recently introduced at Neural Computing and Applications 2016. Its versatility was illustrated by building a public-key encryption scheme. We propose an algebraic key-recovery attack in the polynomial computational complexity. Furthermore, we peel off the encryption and decryption process and propose attack methods for solving the conjugator search problem over the given non-abelian group. Finally, we provide corresponding practical attack examples to illustrate the attack methods in our cryptanalysis, and provide some improved suggestions.

A LINEARIZATION ATTACK ON MODIFIED E_0 ALGORITHM

A linearization attack on the Key Stream Generator （KSG） of the modified Eo algorithm proposed by Hermelin [Proceedings of ICISC＇99, Springer LNCS 1787, 2000, 17-29] is given in this paper. The initial value can be recovered by a linearization attack with O（2^60.52） operations by solving a System of Linear Equations （SLE） with at most 2^20.538 unknowns. Frederik Armknecht [Cryptology ePrint Archive, 2002/191] proposed a linearization attack on the KSG olEo algorithm with O（2^70.341） operations by solving an SLE with at most 2^24.056 unknowns, so the modification proposed by Hermelin reduces the ability or E0 to resist the linearization attack by comparing with the results ofFrederik Armknecht.