流密码

构造一个一样的串:

解答： 

周期展开，整体异或

'''
@Time : 2020/10/8 16:17
@Author : laolao
@FileName: 流密码.py
P17页
'''


def Page_17():
    a = [1, 0, 0, 1, 1]
    s = []
    for i in range(35):
        # t=a[0]
        # for j in range(1,5):
        #     t=t^a[j]
        t = a[0] ^ a[3]
        print(a)
        s.append(a[0])
        a.pop(0)
        a.append(t)
        print("输出序列：{}".format(s))


def Homework():
    a = [1, 0, 1]
    s = []
    for i in range(32):
        t = a[2] ^ a[0]
        print(a)
        s.append(a[0])
        a.pop(0)
        a.append(t)
        print("输出序列：{}".format(s))
    return s


def Same_Homework():
    a = [1, 0, 1, 0, 0, 1]
    s = []
    for i in range(32):
        # t = a[0] ^ a[2]
        t=a[0]
        for j in range(1,len(a)):
            t=t^a[j]
        print(a)
        s.append(a[0])
        a.pop(0)
        a.append(t)
        print("输出序列：{}".format(s))
    return s


if __name__ == '__main__':
    s1 = Homework()
    s2 = Same_Homework()
    print("*" * 50)
    print("目标：{}".format(s1))
    print("构造：{}".format(s2))

 书本定理2-1证明：