指数函数之特性(续) 3.交换性 指数函数满足交换性,因为 Ex(ey(g)=Ex(g)=(gy)x=gyx y(Ex(g)=Ey(gx)=(gx)Y=g x(E√g) ))=Ey(Ex(g)) 0(0 ash mfy@ustc.edu.cn 现代密码学理论与实践 19/81mfy@ustc.edu.cn 现代密码学理论与实践 19/81 3. 交换性 指数函数满足交换性, 因为: Ex(Ey(g))=Ex(gy )=(gy ) x=gyx Ey(Ex(g))=Ey(gx)=(gx) y=gxy ∴ Ex(Ey(g))=Ey(Ex(g))