Iterative Characteristics of DES and S^2-DES

In this paper we show that we are close at the proof that the type of characteristics used by Biham and Shamir in their differential attack on DES are in fact the best characteristics we can find for DES. Furthermore we show that the criteria for the construction of DES-like S-boxes proposed by Kim are insufficient to assure resistance against differential attacks. We show several good iterative characteristics for these S-boxes to be used in differential attacks. Finally we examine the probabilities of the two characteristics used by Biham and Shamir. We found that for some keys we do not get the probabilities used in the attack. We suggest the use of 5 characteristics instead of two in the attack on DES

Likelihood Estimation for Block Cipher Keys

In this paper, we give a general framework for the analysis of block ciphers using the statistical technique of likelihood estimation. We show how various recent successful cryptanalyses of block ciphers can be regarded in this framework. By analysing the SAFER block cipher in this framework we expose a cryptographic weakness of that cipher

An encryption package for UNIX

Cryptography has a much wider application than secrecy, such as authentication and digital signature. There are two common types of cryptographic algoritlims - symmetric and asymmetric. The Data Encryption Standaid (DES) is the first and only, publicly available cryptographic algoritlim tliat has been widely used in commercial conmiunication. The DES is a block cipher symmetric algoritlim and its design is based on the Shannon\u27s two general principles - diffusion and confusion. With the decreased cost of hardware and a better understanding of block ciphers and cryptanalysis techniques, a number of DES-like ciphers have been proposed as the replacement for DES. One-way hashing functions are useful in implementing any digital signature schemes. A hashing function accepts a vai\u27iable size message M as input and outputs a fixed size representation of tlie message H(M). A number of hashing functions of fixed size or variable size message digest have been proposed. The cryptographic primitives (des, feal, loki, kliufu, and kliafre), block cipher based hashing algorithms (sbh and dbh), and key-less hashing algorithms (md4, md4x, md5 and haval) have been implemented as standard commands and C library calls for the UNIX Operating System

Differential Cryptanalysis of Feistel’s Iterated Block Ciphers

В статті обговорюються базові принципи Диференційного криптоаналіза, концепції, алгоритми, ідеї і методи, які забезпечують цей тип атаки, а також математичне обгрунтування.Here are described the basic principles of Differential Cryptanalysis, concepts, algorithms, ideas and methods which provide this kind of attack and also its mathematical background

Cipher Text to Be Transmitted and Cryptanalysis in Network Security

Abstract-In this paper, we propose an encryption algorithm to encrypt plaintext to cipher text. We divide plaintext into numeric and non-numeric fields, also, we pack the numeric fields to produce packed numeric table and combine it with symbol fields to produce the new plaintext. We apply the basic computing operations, e.g., inserting dummy symbols, rotating, transposition, shifting and complement, in the proposed algorithm to encrypt plaintext to cipher text. The produced the cipher text which contains the plaintext, relative data and tables of encryption is transmitted to the receiver through the network. We also propose the cryptanalysis about these algorithms. It can be shown that the proposed algorithm is more secure in network security

The design of a secure data communication system

The recent results of using a new type of chosen-plaintext attack, which is called differential cryptanalysis, makes most published conventional secret-key block cipher systems vulnerable. The need for a new conventional cipher which resists all known attacks was the main inspiration of this work. The design of a secret-key block cipher algorithm called DCU-Cipher, that resists all known cryptanalysis methods is proposed in this dissertation. The proposed method is workable for either 64-bit plaintext/64-bit ciphertext blocks, or 128-bit plaintext/128-bit ciphertext blocks. The secret key in both styles is 128-bit long. This method has only four rounds and the main transformation function in this cipher algorithm is based on four mixed operations. The proposed method is suitable for both hardware and software implementation. It is also suitable for cryptographic hash function implementations. Two techniques for file and/or data communication encryption are also proposed here. These modes are modified versions of the Cipher-Block Chaining mode, by which the threat of the known-plaintext differential cyptanalytical attack is averted. An intensive investigation of the best known Identity-based key exchange schemes is also presented. The idea behind using such protocols, is providing an authenticated secret-key by using the users identification tockens. These kind of protocols appeared recently and are not standardized as yet. None of these protocols have been compared with previous proposals. Therefore one can not realize the efficiency and the advantages of a new proposed protocol without comparing it with other existing schemes of the same type. The aim of this investigation is to clarify the advantages and the disadvantages of each of the best known schemes and compare these schemes from the complixity and the speed viewpoint

Fast, parallel and secure cryptography algorithm using Lorenz's attractor

A novel cryptography method based on the Lorenz's attractor chaotic system is presented. The proposed algorithm is secure and fast, making it practical for general use. We introduce the chaotic operation mode, which provides an interaction among the password, message and a chaotic system. It ensures that the algorithm yields a secure codification, even if the nature of the chaotic system is known. The algorithm has been implemented in two versions: one sequential and slow and the other, parallel and fast. Our algorithm assures the integrity of the ciphertext (we know if it has been altered, which is not assured by traditional algorithms) and consequently its authenticity. Numerical experiments are presented, discussed and show the behavior of the method in terms of security and performance. The fast version of the algorithm has a performance comparable to AES, a popular cryptography program used commercially nowadays, but it is more secure, which makes it immediately suitable for general purpose cryptography applications. An internet page has been set up, which enables the readers to test the algorithm and also to try to break into the cipher in