中文摘要：

该文分析研究了LBlock分组密码算法的不可能差分性质。基于LBlock算法的轮函数结构和部分密钥分别猜测技术，给出了21轮和22轮的LBlock算法的不可能差分分析方法。攻击21轮LBlock算法所需的数据量约为262，计算量约为262次21轮加密；攻击22轮LBlock算法所需的数据量约为262.5，计算量约为263.5次22轮加密。与已有的结果相比较，分析所需的计算量均有明显的降低，是目前不可能差分分析攻击LBlock的最好结果。

英文摘要：

The impossible differential property of LBlock block cipher is analyzed. Based on the property ot the structure of round function and the technology of key-byte guessing, two impossible differential attacks on 21-round and 22-round reduced LBlock are presented. It is shown that the attack on 21-round requires about 262 chosen plaintexts and 262 21-round encryptions, and on 22-round requires about 262.5 chosen plaintexts and 263.5 22-round encryptions. The presented results are the best impossible differential attack on reduced-round LBlock so far.