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In cryptography, Achterbahn is the name of a synchronous stream cipher algorithm submitted to the eSTREAM Project of the eCRYPT network. In the final specification the cipher is called ACHTERBAHN-128/80, because it supports the key lengths of 80 bits and 128 bits, respectively . Achterbahn was developed by Berndt Gammel, Rainer Göttfert and Oliver Kniffler. ''Achterbahn'' means ''rollercoaster'' (in German), though a literal translation of the term would be ''eight-track'', which indicates that the cipher can encrypt eight bit streams in parallel. The parameters of the cipher are given in the following table: ACHTERBAHN-128 is downward compatible and can produce the same keystream as ACHTERBAHN-80 if so desired. The keystream generator of ACHTERBAHN-128/80 is based on the design principle of the nonlinear combination generator, however it deploys primitive nonlinear feedback shift registers (NLFSR) instead of linear ones (LFSR). ==Security== There are no known cryptanalytic attacks against ACHTERBAHN-128/80 for the tabulated parameters that are faster than brute force attack. Recent analysis showed that attacks are possible if larger frame (packet) lengths are used in a communication protocol . A recommendation for a maximum frame length of 244 bit is given in Ref. This value does however not imply practical limitations. 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「Achterbahn」の詳細全文を読む スポンサード リンク
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