📜  换位密码(1)

📅  最后修改于: 2023-12-03 14:54:41.815000             🧑  作者: Mango

换位密码介绍

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。

常见的换位密码算法
列置换密码

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

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

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

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

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

代码示例
列排列密码加解密代码
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
列移位密码加解密代码
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
行列混淆密码加解密代码
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
总结

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。