如何使用PN序列将明文加密为密文

Question

我正在尝试创建一个函数，该函数使用PN序列将纯文本加密为密文。但我不知道该怎么做。有人有什么算法可以帮助我创建一个函数，帮助我构建加密函数吗。

Answer 1

此代码使用LFSR移位寄存器获得伪随机序列，然后将其与明文异或以获得密文。该代码使用pylfsr和numpy。

from pylfsr import LFSR
# The initial state
state = [0,0,0,1,0,1,0,1,0,1,1]
# The LFSR polynomial use a primitive polynomail to get maximum period length
poly = [5, 4, 3, 2]
l = LFSR(fpoly=poly, initstate =state)
message = b"This is a Test Message"
ciphertext = b""
# generate all LFSR sequence
allseq = l.runFullCycle()
seq = ""
seq_index = 0
# Convert LFSR bits into a string
for x in allseq:
seq += str(x)
for counter in range(len(message)):
ran_seq = seq[seq_index: seq_index+8]
# Now encrypt by XOR convert to bytes and append to ciphertext
ciphertext += bytes([int(message[counter]) ^ int(ran_seq, 2)])
seq_index += 8  # Move sequence to Next byte
print(ciphertext)
plaintext = b""
# Reset The LFSR sequence to start from beginning
seq_index = 0
for counter in range(len(ciphertext)):
ran_seq = seq[seq_index: seq_index+8]
plaintext += bytes([int(ciphertext[counter]) ^ int(ran_seq, 2)])
seq_index += 8
print(plaintext)