Topic
Differential cryptanalysis
About: Differential cryptanalysis is a research topic. Over the lifetime, 2131 publications have been published within this topic receiving 54681 citations.
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08 May 2016
TL;DR: In this paper, the authors proposed a new stream cipher construction that allows constant and smaller noise by applying a Boolean filter function to a public bit permutation of a constant key register, so that the Boolean complexity of the stream cipher outputs is constant.
Abstract: Symmetric ciphers purposed for Fully Homomorphic Encryption FHE have recently been proposed for two main reasons. First, minimizing the implementation time and memory overheads that are inherent to current FHE schemes. Second, improving the homomorphic capacity, i.e. the amount of operations that one can perform on homomorphic ciphertexts before bootstrapping, which amounts to limit their level of noise. Existing solutions for this purpose suggest a gap between block ciphers and stream ciphers. The first ones typically allow a constant but small homomorphic capacity, due to the iteration of rounds eventually leading to complex Boolean functions hence large noise. The second ones typically allow a larger homomorphic capacity for the first ciphertext blocks, that decreases with the number of ciphertext blocks due to the increasing Boolean complexity of the stream ciphers' output. In this paper, we aim to combine the best of these two worlds, and propose a new stream cipher construction that allows constant and smaller noise. Its main idea is to apply a Boolean filter function to a public bit permutation of a constant key register, so that the Boolean complexity of the stream cipher outputs is constant. We also propose an instantiation of the filter function designed to exploit recent 3rd-generation FHE schemes, where the error growth is quasi-additive when adequately multiplying ciphertexts with the same amount of noise. In order to stimulate further investigation, we then specify a few instances of this stream cipher, for which we provide a preliminary security analysis. We finally highlight the good properties of our stream cipher regarding the other goal of minimizing the time and memory complexity of calculus delegation for 2nd-generation FHEi¾?schemes. We conclude the paper with open problems related to the large design space opened by these new constructions.
99 citations
31 May 1998
TL;DR: This paper shows a drastic improvement of the results of several previous attempts of cryptanalysis of RC5 due to a novel partial differential approach and shows that the 64 bit word version of this cipher is also much weaker than it was expected.
Abstract: RC5 is a fast block cipher designed by Ron Rivest in 1994. Since then several attempts of cryptanalysis of this cipher were published. The best previously known attack requires 254 chosen plaintexts in order to derive the full set of 25 subkeys for the 12 round RC5 with 32 bit words. In this paper we show a drastic improvement of these results due to a novel partial differential approach. Our attack requires 244 chosen plaintexts. We show that the 64 bit word version of RC5 is also much weaker than it was expected.
98 citations
04 Nov 2009
TL;DR: Two new ways to mount attacks on the SHA-3 candidates Grostl, and ECHO, and apply these attacks also to the AES are proposed and an improved known-key distinguisher for 7 rounds of the AES block cipher and the internal permutation used in ECHO is presented.
Abstract: In this paper, we propose two new ways to mount attacks on the SHA-3 candidates Grostl, and ECHO, and apply these attacks also to the AES. Our results improve upon and extend the rebound attack. Using the new techniques, we are able to extend the number of rounds in which available degrees of freedom can be used. As a result, we present the first attack on 7 rounds for the Grostl-256 output transformation and improve the semi-free-start collision attack on 6 rounds. Further, we present an improved known-key distinguisher for 7 rounds of the AES block cipher and the internal permutation used in ECHO.
97 citations