Abstract. SHACAL is a 160-bit block cipher based on the hash standard SHA-1, as a submission to NESSIE. SHACAL uses the XOR, modular addition operation and the functions of bit-by-bit manner. These operations and functions make the differential cryptanalysis difficult, i.e, it is hard to find a long differential characteristic with high probability. But, we can find short differential characteristics with high probabilities. Using this fact, we discuss the security of SHACAL against an amplified boomerang attack. We find a 36-step boomerang-distinguisher and present attacks on reduced-round SHACAL with various key sizes. We can attack 39-step SHACAL with 256-bit key, and 47-step SHACAL with 512-bit key. In addition, we present differential attacks of reduced-round SHACAL with various key sizes.
We present the impossible differential cryptanalysis of the block cipher XTEA[7] and TEA[6]. The core of the design principle of these block ciphers is an easy implementation and a simplicity. But this simplicity dose not offer a large diffusion property. Our impossible differential cryptanalysis of reduced-round versions of XTEA and TEA is based on this fact. We will show how to construct a 12-round impossible characteristic of XTEA. We can then derive 128-bit user key of the 14round XTEA with 2 62.5 chosen plaintexts and 2 85 encryption times using the 12-round impossible characteristic. In addition, we will show how to construct a 10-round impossible characteristic of TEA. Then we can derive 128-bit user key of the 11-round TEA with 2 52.5 chosen plaintexts and 2 84 encryption times using the 10-round impossible characteristic.
Abstract. This paper describes a new software-efficient 256-bit hash function, FORK-256. Recently proposed attacks on MD5 and SHA-1 motivate a new hash function design. It is designed not only to have higher security but also to be faster than SHA-256. The performance of the new hash function is at least 30% better than that of SHA-256 in software. And it is secure against any known cryptographic attacks on hash functions.
Abstract. We apply the algebraic attacks on stream ciphers with memories to the summation generator. For a summation generator that uses n LFSRs, an algebraic equation relating the key stream bits and LFSR output bits can be made to be of degree less than or equal to 2 log 2 n , using log 2 n + 1 consecutive key stream bits. This is much lower than the upper bound given by previous general results. We also show that the techniques of [6,2] can be applied to summation generators using 2 k LFSRs to reduce the effective degree of the algebraic equation.
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