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

Linear cryptanalysis of pseudorandom functions

Relatório de projeto de pesquisa.In this paper, we study linear relations propagating across block ciphers from the key input to the ciphertext (for a fixed plaintext block). This is a usual setting of a one-way function, used for instance in modes of operation such as KFB (key feedback). We instantiate the block cipher with the full 16-round DES and $s^2$-DES, 10-round LOKI91 and 24-round Khufu, for which linear relations with high bias are well known. Other interesting targets include the full 8.5-round IDEA and PES ciphers for which high bias linear relations exist under the assumption of weak keys. Consequences of these findings impact the security of modes of operation such as KFB and of pseudorandom number/bit generators. These analyses were possible due to the linear structure and the poor diffusion of the key schedule algorithms. These findings shall motivate carefull (re)design of current and future key schedule algorithms

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

S-Box Reverse-Engineering: Boolean Functions, American/Russian Standards, and Butterflies

International audienc

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

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

Statistical cryptanalysis of block ciphers

Since the development of cryptology in the industrial and academic worlds in the seventies, public knowledge and expertise have grown in a tremendous way, notably because of the increasing, nowadays almost ubiquitous, presence of electronic communication means in our lives. Block ciphers are inevitable building blocks of the security of various electronic systems. Recently, many advances have been published in the field of public-key cryptography, being in the understanding of involved security models or in the mathematical security proofs applied to precise cryptosystems. Unfortunately, this is still not the case in the world of symmetric-key cryptography and the current state of knowledge is far from reaching such a goal. However, block and stream ciphers tend to counterbalance this lack of "provable security" by other advantages, like high data throughput and ease of implementation. In the first part of this thesis, we would like to add a (small) stone to the wall of provable security of block ciphers with the (theoretical and experimental) statistical analysis of the mechanisms behind Matsui's linear cryptanalysis as well as more abstract models of attacks. For this purpose, we consider the underlying problem as a statistical hypothesis testing problem and we make a heavy use of the Neyman-Pearson paradigm. Then, we generalize the concept of linear distinguisher and we discuss the power of such a generalization. Furthermore, we introduce the concept of sequential distinguisher, based on sequential sampling, and of aggregate distinguishers, which allows to build sub-optimal but efficient distinguishers. Finally, we propose new attacks against reduced-round version of the block cipher IDEA. In the second part, we propose the design of a new family of block ciphers named FOX. First, we study the efficiency of optimal diffusive components when implemented on low-cost architectures, and we present several new constructions of MDS matrices; then, we precisely describe FOX and we discuss its security regarding linear and differential cryptanalysis, integral attacks, and algebraic attacks. Finally, various implementation issues are considered