指数函数之特性(续) 4.非对称性( Asymmetric property) Ex(-g)=(-g)x=(-1)xgx=(-1)XEx(g) 若X为偶,则E(-g)=Ex(g) 若X为奇,则E(-g)=-Ex(g) 5.乘法性( Multiplicative property) Ex(g)Ex(g2)=g, x=(g1g2)x=Ex(,g2) 0(0 ash mfy@ustc.edu.cn 现代密码学理论与实践 20/81mfy@ustc.edu.cn 现代密码学理论与实践 20/81 4. 非对称性(Asymmetric Property) ∵Ex(-g)=(-g)x=(-1)xgx=(-1)xEx(g) ∴若x为偶，则Ex(-g)= Ex(g) 若x为奇，则Ex(-g)= -Ex(g) 5. 乘法性(Multiplicative Property) Ex(g1 )Ex(g2 )=g1 xg2 x=(g1g2 ) x=Ex(g1g2 )