LFSR python实现

一.LFSR部分（线性反馈移位寄存器）

LFSR的优点：
a.非常适合硬件实现
b.能产生大的周期序列
c.能产生好的统计特性的序列
d.能应用代数方法进行分析

实现思路：
a是n个寄存器（状态）
c是种子密钥，对应着a的系数

输出是a1&cn
迭代方程为：
ai(t+1）=ai+1（t）（i=1,2,…,n-1)
an(t+1)=Σ(ci*an-i(t))

class LFSR():
    def __init__(self, c=None, a=None, lenc=0): #c是开关（系数），a是初始状态 
        if a is None:
            a = []
        if c is None:
            c = []
        self.a = a
        self.c = c
        self.lenc = lenc
        lena = len(a)
        #如果lena比lenc短，那么将其拓展 
        

    def LeftShift(self):
        lastb = 0
        lenc = self.lenc
        for i in range(lenc):
            lastb = lastb ^ (self.a[i] & self.c[i])
        b = self.a[1:]
        b.append(lastb)
        outp = self.a[0]   
        #体现linear  
        self.a = b
        return outp

二.j-k触发器

j-k触发器有两个输入，对应着两个LFSR生成的序列输出
JK触发器的输出方程： ck = ak ^ (~(ak ^ bk) & ck-1)

class cypto_LFSR():
    def __init__(self, key, lfsr1 = None, lfsr2 = None):
        if lfsr1 is None:
            lfsr1 = [0, 1, 0, 1]
        if lfsr2 is None:
            lfsr2 = [0, 0, 1, 1]
        Keymap = key
        lenk = len(Keymap)
        self.lfsr1 = LFSR(Keymap, lfsr1, lenk)
        self.lfsr2 = LFSR(Keymap, lfsr2, lenk)  #生成LFSR伪随机序列 
        self.Key = Keymap
        self.lc = 0

    def GetBit(self):
        ak = self.lfsr1.LeftShift()
        bk = self.lfsr2.LeftShift()
        ck = ak ^ (~(ak ^ bk) & self.lc)  # JK触发器
        self.lc = ck
        return int(ck)

    def do_crypt(self, LFSR_msg):
        text = []
        for i in LFSR_msg:
            j, cnt = i, 8
            tmp = []
            while cnt > 0:
                tmp.append(self.GetBit() ^ (j & 1))#低位放在了前面 
                j = j >> 1
                cnt = cnt - 1
            res = 0
            for iti in range(7, -1, - 1):#按照[7，6，5，4，3，2，1]的顺序 
                res = res << 1
                res = res + tmp[iti]
            text.append(res)
        return bytes(text)

三.完整代码

# -*- coding: utf-8 -*-
"""
Created on Mon Dec 21 10:41:08 2020

@author: 15061
"""
import base64
def get_str_bits( s:str):
    list_b = []
    for i in s:
        list_b.append((ord(i) - ord('0')))
    return list_b
class LFSR():
    def __init__(self, c=None, a=None, lenc=0): #c是开关（系数），a是初始状态 
        if a is None:
            a = []
        if c is None:
            c = []
        self.a = a
        self.c = c
        self.lenc = lenc
        lena = len(a)
        #如果lena比lenc短，那么将其拓展 
        

    def LeftShift(self):
        lastb = 0
        lenc = self.lenc
        for i in range(lenc):
            lastb = lastb ^ (self.a[i] & self.c[i])
        b = self.a[1:]
        b.append(lastb)
        outp = self.a[0]   
        #体现linear  
        self.a = b
        return outp


class cypto_LFSR():
    def __init__(self, key, lfsr1 = None, lfsr2 = None):
        if lfsr1 is None:
            lfsr1 = [0, 1, 0, 1]
        if lfsr2 is None:
            lfsr2 = [0, 0, 1, 1]
        Keymap = key
        lenk = len(Keymap)
        self.lfsr1 = LFSR(Keymap, lfsr1, lenk)
        self.lfsr2 = LFSR(Keymap, lfsr2, lenk)  #生成LFSR伪随机序列 
        self.Key = Keymap
        self.lc = 0

    def GetBit(self):
        ak = self.lfsr1.LeftShift()
        bk = self.lfsr2.LeftShift()
        ck = ak ^ (~(ak ^ bk) & self.lc)  # JK触发器
        self.lc = ck
        return int(ck)

    def do_crypt(self, LFSR_msg):
        text = []
        for i in LFSR_msg:
            j, cnt = i, 8
            tmp = []
            while cnt > 0:
                tmp.append(self.GetBit() ^ (j & 1))#低位放在了前面 
                j = j >> 1
                cnt = cnt - 1
            res = 0
            for iti in range(7, -1, - 1):#按照[7，6，5，4，3，2，1]的顺序 
                res = res << 1
                res = res + tmp[iti]
            text.append(res)
        return bytes(text)
s="i_love_hnu"

k="1001"
key=get_str_bits(k)
l=cypto_LFSR(key)
print(l.do_crypt(get_str_bits(s)))

标签：lenc,None,python,LFSR,self,lfsr2,实现,lfsr1
来源： https://blog.csdn.net/qq_44109982/article/details/111488199