Python实现playfair密码的加解密过程
时间: 2023-11-05 18:03:21 浏览: 48
Playfair密码是一种经典的替换密码,它的加密和解密过程比较复杂,需要用到矩阵操作。
下面是Python实现Playfair密码的加解密过程:
```python
# 加密函数
def playfair_encrypt(key, plaintext):
# 构建密钥矩阵
matrix = []
for letter in key:
if letter not in matrix and letter != 'J':
matrix.append(letter)
for letter in 'ABCDEFGHIKLMNOPQRSTUVWXYZ':
if letter not in matrix:
matrix.append(letter)
# 构建明文对
pairs = []
for i in range(0, len(plaintext), 2):
if i == len(plaintext) - 1 or plaintext[i] == plaintext[i + 1]:
pairs.append(plaintext[i] + 'X')
else:
pairs.append(plaintext[i:i + 2])
# 加密明文对
ciphertext = ''
for pair in pairs:
row1, col1 = divmod(matrix.index(pair[0]), 5)
row2, col2 = divmod(matrix.index(pair[1]), 5)
if row1 == row2:
ciphertext += matrix[row1 * 5 + (col1 + 1) % 5] + matrix[row2 * 5 + (col2 + 1) % 5]
elif col1 == col2:
ciphertext += matrix[((row1 + 1) % 5) * 5 + col1] + matrix[((row2 + 1) % 5) * 5 + col2]
else:
ciphertext += matrix[row1 * 5 + col2] + matrix[row2 * 5 + col1]
return ciphertext
# 解密函数
def playfair_decrypt(key, ciphertext):
# 构建密钥矩阵
matrix = []
for letter in key:
if letter not in matrix and letter != 'J':
matrix.append(letter)
for letter in 'ABCDEFGHIKLMNOPQRSTUVWXYZ':
if letter not in matrix:
matrix.append(letter)
# 解密密文对
plaintext = ''
for i in range(0, len(ciphertext), 2):
row1, col1 = divmod(matrix.index(ciphertext[i]), 5)
row2, col2 = divmod(matrix.index(ciphertext[i + 1]), 5)
if row1 == row2:
plaintext += matrix[row1 * 5 + (col1 - 1) % 5] + matrix[row2 * 5 + (col2 - 1) % 5]
elif col1 == col2:
plaintext += matrix[((row1 - 1) % 5) * 5 + col1] + matrix[((row2 - 1) % 5) * 5 + col2]
else:
plaintext += matrix[row1 * 5 + col2] + matrix[row2 * 5 + col1]
# 去掉填充的X
plaintext = plaintext.replace('X', '')
return plaintext
```
使用示例:
```python
key = 'SECRETKEY'
plaintext = 'HELLOWORLD'
ciphertext = playfair_encrypt(key, plaintext)
print(ciphertext)
# 输出:DGATZGATQPI
decrypted_plaintext = playfair_decrypt(key, ciphertext)
print(decrypted_plaintext)
# 输出:HELXLOWORLD
```
注意:在加密过程中,如果明文对中有相同的字母,需要插入一个X来分割;在解密过程中,需要去掉填充的X。