We study known-key distinguishing and partial-collision attacks on GFN-2 structures with various block lengths in this paper. For 4-branch GFN-2, we present 15-round known-key distinguishing attack and 11-round partial-collision attack which improve previous results. We also present 17-round known-key distinguishing attack on 6-branch GFN-2 and 27-round known-key distinguishing attack on 8-branch GFN-2 and show that several partial-collision attacks are derived from them. Additionally, some attacks are valid under special conditions for the F-function.

中文翻译：

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具有SP F功能的GFN-2的已知密钥区分和部分冲突攻击

本文研究了具有不同块长的GFN-2结构的已知密钥区分和部分冲突攻击。对于4分支GFN-2，我们提出了15轮已知密钥区分攻击和11轮局部冲突攻击，这改善了先前的结果。我们还提出了针对6分支GFN-2的17轮已知密钥区分攻击和针对8分支GFN-2的27轮已知密钥区分攻击，并显示了从中衍生出的几种部分冲突攻击。此外，某些攻击在特殊条件下对于F功能有效。