📅  最后修改于: 2023-12-03 14:54:41.815000             🧑  作者: Mango
换位密码(Transposition Cipher)是一种基于置换的密码算法,它将明文中的字母按照一定规律重新排列,形成密文。换位密码的安全性取决于排列规则的复杂度,但相对于替换密码等其他简单的密码算法来说,换位密码具有更高的安全性。
列置换密码是一种基于矩阵变换的换位密码,将明文分成若干列,然后按照一定的规则重新排列列,形成密文。常见的列置换算法有如下几种:
列排列密码将明文分成若干列,然后按照一定的规则重新排列列,形成密文。解密时需要恢复列的原始顺序。
示例:
明文:HELLO WORLD
列数:4
列排列规则:4 2 1 3
加密过程:
H L W
E O O
L R R
L D
密文:HLWEOLORRLD
解密过程:
H E L
L O R
L O R
O W D
明文:HELLOWORLD
列移位密码将明文分成若干列,然后将每一列向下移动若干个位置,形成密文。解密时需要恢复列的原始位置。
示例:
明文:HELLO WORLD
列数:4
列移位距离:2
加密过程:
H L O D
E W R
L O
L R
密文:HLEOLDWRLOR
解密过程:
H L W
E O O
L R R
L D
明文:HELLO WORLD
行置换密码是一种基于行变换的换位密码,将明文中的每一个字母都放置于矩阵的某个位置,然后按照一定的规则重新排列行,形成密文。常见的行置换算法有如下几种:
行列混淆密码将明文中的每一个字母都放置于矩阵的某个位置,然后将每一行向下移动若干个位置,每一列向右移动若干个位置,形成密文。解密时需要恢复行列的原始位置。
示例:
明文:HELLO WORLD
行列数:4
行移位距离:2
列移位距离:1
加密过程:
L O H D L R W E O L
L O R
密文:LOHDLRWEOLOLR
解密过程:
H E L
L O R
L O R
O W D
明文:HELLO WORLD
def column_permutation_encrypt(plain_text, col_order):
nrows = (len(plain_text) - 1) // col_order + 1
matrix = [''] * nrows
for i, char in enumerate(plain_text):
matrix[i % nrows] += char
cipher_text = ''
for col in col_order:
cipher_text += matrix[col - 1]
return cipher_text
def column_permutation_decrypt(cipher_text, col_order):
nrows = (len(cipher_text) - 1) // len(col_order) + 1
matrix = [''] * nrows
index = 0
for col in col_order:
count = len(cipher_text) // len(col_order)
if index < len(cipher_text) % len(col_order):
count += 1
matrix[col - 1] = cipher_text[index : index + count]
index += count
plain_text = ''
for i in range(nrows):
for col in range(len(col_order)):
if i < len(matrix[col]):
plain_text += matrix[col][i]
return plain_text
def column_shift_encrypt(plain_text, col_count, shift_distance):
nrows = (len(plain_text) - 1) // col_count + 1
matrix = [''] * nrows
for i, char in enumerate(plain_text):
matrix[i % nrows] += char
cipher_text = ''
for col in range(col_count):
rows = matrix[col][shift_distance:] + matrix[col][:shift_distance]
cipher_text += rows
return cipher_text
def column_shift_decrypt(cipher_text, col_count, shift_distance):
plain_text = ''
index = 0
for col in range(col_count):
rows = cipher_text[index:index + len(cipher_text) // col_count]
index += len(cipher_text) // col_count
if col < len(cipher_text) % col_count:
rows += cipher_text[index]
index += 1
shift = shift_distance % len(rows)
row_count = len(rows) // shift + 1
matrix = [''] * row_count
for i, char in enumerate(rows):
matrix[i % row_count] += char
for row in range(row_count):
if row < len(matrix):
plain_text += matrix[row][(shift - shift_distance) % len(matrix[row])]
return plain_text
def row_column_permutation_encrypt(plain_text, row_count, col_count, row_order, col_order):
matrix = [[''] * col_count for _ in range(row_count)]
index = 0
for col in col_order:
for row in row_order:
if index < len(plain_text):
matrix[row - 1][col - 1] = plain_text[index]
index += 1
cipher_text = ''
for row in row_order:
cipher_text += ''.join(matrix[row - 1])
cipher_text = ''.join([''.join([cipher_text[col_count * row + col] for row in range(row_count)]) for col in range(col_count)])
return cipher_text
def row_column_permutation_decrypt(cipher_text, row_count, col_count, row_order, col_order):
plain_text = ''
index = 0
matrix = [[''] * col_count for _ in range(row_count)]
for col in range(col_count):
for row in range(row_count):
if row < len(row_order) and col < len(col_order):
matrix[row_order[row] - 1][col_order[col] - 1] = cipher_text[index]
index += 1
cipher_text = ''.join([''.join([matrix[row][col] for row in row_order]) for col in col_order])
for row in range(row_count):
plain_text += ''.join([matrix[row][col] for col in range(col_count) if matrix[row][col]])
return plain_text
换位密码是一种较为复杂的密码算法,常见的算法有列置换密码和行置换密码。在实际应用中,换位密码还可以和其他密码算法结合使用,以加强密码的安全性。