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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Fast Syndrome Based Hash ： ウィキペディア英語版 Fast Syndrome Based Hash In cryptography, the Fast Syndrome-based hash Functions (FSB) are a family of cryptographic hash functions introduced in 2003 by Daniel Augot, Matthieu Finiasz, and Nicolas Sendrier. 〔 〕 Unlike most other cryptographic hash functions in use today, FSB can to a certain extent be proven to be secure. More exactly, it can be proven that breaking FSB is at least as difficult as solving a certain NP-complete problem known as Regular Syndrome Decoding so FSB is provably secure. Though it is not known whether NP-complete problems are solvable in polynomial time, it is often assumed that they are not. Several versions of FSB have been proposed, the latest of which was submitted to the SHA-3 cryptography competition but was rejected in the first round. Though all versions of FSB claim provable security, some preliminary versions were eventually broken. 〔 〕 The design of the latest version of FSB has however taken this attack into account and remains secure to all currently known attacks. As usual, provable security comes at a cost. FSB is slower than traditional hash functions and uses quite a lot of memory, which makes it impractical on memory constrained environments. Furthermore, the compression function used in FSB needs a large output size to guarantee security. This last problem has been solved in recent versions by simply compressing the output by another compression function called Whirlpool. However, though the authors argue that adding this last compression does not reduce security, it makes a formal security proof impossible. 〔 〕 == Description of the hash function == We start with a compression function $\backslash phi$ with parameters $$ such that $n\; >\; w$ and $w\; \backslash log(n/w)\; >\; r$. This function will only work on messages with length $s\; =\; w\backslash log(n/w)$; $r$ will be the size of the output. Furthermore, we want $n,r,w,s$ and $\backslash log(n/w)$ to be natural numbers, where $\backslash log$ denote the binary logarithm. The reason for $w\; \backslash cdot\; \backslash log(n/w)\; >\; r$ is that we want $\backslash phi$ to be a compression function, so the input must be larger than the output. We will later use the Merkle-Damgård construction to extend the domain to inputs of arbitrary lengths. The basis of this function consists of a (randomly chosen) binary $r\; \backslash times\; n$ matrix $H$ which acts on a message of $n$ bits by matrix multiplication. Here we encode the $w\backslash log(n/w)$-bit message as a vector in $(\backslash mathbf\_2)^n$, the $n$-dimensional vector space over the field of two elements, so the output will be a message of $r$ bits. For security purposes as well as to get a faster hash speed we want to use only “regular words of weight $w$” as input for our matrix. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fast Syndrome Based Hash」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.