中文摘要：

基于有限域求逆实现S盒的方法存在求逆运算复杂、硬件实现难的问题．为此，通过引入新的复合域，将GF（2^8）域上的求逆运算转化成GF（（（2^2）^2）^2）复合域上的求逆运算，提出了一种基于复合域求逆的低电路面积开销的S盒构造方法．该方法通过采用复合域计算、优化运算顺序和复用公因子等手段减小S盒硬件实现的电路面积．实验表明，在0．18μm和0．35μmCMOS工艺下，采用基于复合域求逆构造的S盒与采用查找表方法构造的S盒相比，电路面积可减少34％～68％．此外，在相同的工艺和吞吐率下，与原始的算法相比，采用提出的S盒的SMS4算法硬件资源消耗大大减少，适用于对芯片面积严格限制的场合．

英文摘要：

In order to solve the problem of the implementation algorithm of S-box based on the inversion transformation over Galois field, methods such as composite field computation, altering calculation order and sharing factors have been used to optimize operations. A low hardware overhead implementation algorithm of S-box based on the inversion transformation approach from GF（28） to GF（22） was presented. Compared with the implementations based on look-up table method, this algorithm can reduce circuit area by 34%- 68% using 0. 18 μm and 0. 35 μm CMOS technology. This design method can make SMS4 algorithm more suitable for area-critical devices.