密码学课程设计之线性反馈移位寄存器

 

#coding:utf-8
s = '10001010'#本源多项式x^8+x^4+x^3+x^2+1
a = s
ls = len(s)
for i in range(0,100000):
    s += str(int(s[i])^int(s[i+ls-4])^int(s[i+ls-3])^int(s[i+ls-2]))
t1 = pow(2,ls)-1
t2 = s[ls:].find(a)+ls
print "初始序列长度:%d\n理论最大周期:%d\n实际周期:%d"%(ls,t1,t2)
'''
初始序列长度:8
理论最大周期:255
实际周期:255
'''