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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 Length extension attack ： ウィキペディア英語版 Length extension attack In cryptography and computer security, length extension attacks are a type of attack when certain types of hashes are misused as message authentication codes, allowing for inclusion of extra information. This attack can be done on hashes with construction H(''secret'' ∥ ''message'')〔 when ''message'' and the length of ''secret'' is known. Algorithms like MD5 and SHA-1 that are based on the Merkle–Damgård construction are susceptible to this kind of attack.〔(Flickr API Signature Forgery Vulnerability )〕〔(【引用サイトリンク】title=Hash Length Extension Attacks )〕 Note that since HMAC doesn't use the construction H(''key'' ∥ ''message''), HMAC hashes using susceptible algorithms are not prone to length extension attacks.〔(【引用サイトリンク】title=Stop using unsafe keyed hashes, use HMAC )〕 The SHA-3 algorithm is not susceptible to this attack.〔 〕 == Explanation == The vulnerable hashing functions work by taking the input message, and using it to transform an internal state. After all of the input has been processed, the hash digest is generated by outputting the internal state of the function. It is therefore possible to reconstruct the internal state from the hash digest, which can then be used to process the new data. In this way one may extend the message and compute the hash that is a valid signature for the new message. 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「Length extension attack」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.