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

HeW: AHash Function based on Lightweight Block Cipher FeW

A new hash function HeW: A hash function based on light weight block cipher FeW is proposed in this paper. The compression function of HeW is based on block cipher FeW. It is believed that key expansion algorithm of block cipher slows down the performance of the overlying hash function. Thereby, block ciphers become a less favourable choice to design a compression function. As a countermeasure, we cut down the key size of FeW from 80-bit to 64-bit and provide a secure and efficient key expansion algorithm for the modified key size. FeW based compression function plays a vital role to enhance the efficiency of HeW. We test the hash output for randomness using the NIST statistical test suite and test the avalanche effect, bit variance and near collision resistance. We also give the security estimates of HeW against differential cryptanalysis, length extension attack, slide attack and rotational distinguisher.

MOIM: a novel design of cryptographic hash function

A hash function usually has two main components: a compression function or permutation function and mode of operation. In this paper, we propose a new concrete novel design of a permutation based hash functions called MOIM. MOIM is based on concatenating two parallel fast wide pipe constructions as a mode of operation designed by Nandi and Paul, and presented at Indocrypt 2010 where the size of the internal state is significantly larger than the size of the output. And the permutations functions used in MOIM are inspired from the SHA-3 finalist Grøstl hash function which is originally inspired from Rijndael design (AES). As a consequence there is a very strong confusion and diffusion in MOIM. Also, we show that MOIM resists all the generic attacks and Joux attack in two defense security levels

Inverting Cryptographic Hash Functions via Cube-and-Conquer

MD4 and MD5 are seminal cryptographic hash functions proposed in early 1990s. MD4 consists of 48 steps and produces a 128-bit hash given a message of arbitrary finite size. MD5 is a more secure 64-step extension of MD4. Both MD4 and MD5 are vulnerable to practical collision attacks, yet it is still not realistic to invert them, i.e. to find a message given a hash. In 2007, the 39-step version of MD4 was inverted via reducing to SAT and applying a CDCL solver along with the so-called Dobbertin's constraints. As for MD5, in 2012 its 28-step version was inverted via a CDCL solver for one specified hash without adding any additional constraints. In this study, Cube-and-Conquer (a combination of CDCL and lookahead) is applied to invert step-reduced versions of MD4 and MD5. For this purpose, two algorithms are proposed. The first one generates inversion problems for MD4 by gradually modifying the Dobbertin's constraints. The second algorithm tries the cubing phase of Cube-and-Conquer with different cutoff thresholds to find the one with minimal runtime estimation of the conquer phase. This algorithm operates in two modes: (i) estimating the hardness of a given propositional Boolean formula; (ii) incomplete SAT-solving of a given satisfiable propositional Boolean formula. While the first algorithm is focused on inverting step-reduced MD4, the second one is not area-specific and so is applicable to a variety of classes of hard SAT instances. In this study, 40-, 41-, 42-, and 43-step MD4 are inverted for the first time via the first algorithm and the estimating mode of the second algorithm. 28-step MD5 is inverted for four hashes via the incomplete SAT-solving mode of the second algorithm. For three hashes out of them this is done for the first time.Comment: 40 pages, 11 figures. A revised submission to JAI