古典密码的全部python加密解密

由于古典密码的种类很多，下面只列举了一些常见的古典密码的Python加密解密代码。其中，包括了凯撒密码、仿射密码、维吉尼亚密码、栅栏密码、多倍经典密码等。

凯撒密码

加密代码：

def caesar_cipher(text, key):
    result = ""
    for i in range(len(text)):
        char = text[i]
        if char.isupper():
            result += chr((ord(char) + key - 65) % 26 + 65)
        elif char.islower():
            result += chr((ord(char) + key - 97) % 26 + 97)
        else:
            result += char
    return result

解密代码：

def caesar_decipher(text, key):
    result = ""
    for i in range(len(text)):
        char = text[i]
        if char.isupper():
            result += chr((ord(char) - key - 65) % 26 + 65)
        elif char.islower():
            result += chr((ord(char) - key - 97) % 26 + 97)
        else:
            result += char
    return result

仿射密码

加密代码：

def affine_cipher(text, a, b):
    result = ""
    for i in range(len(text)):
        char = text[i]
        if char.isupper():
            result += chr(((a * (ord(char) - 65) + b) % 26) + 65)
        elif char.islower():
            result += chr(((a * (ord(char) - 97) + b) % 26) + 97)
        else:
            result += char
    return result

解密代码：

def affine_decipher(text, a, b):
    result = ""
    for i in range(len(text)):
        char = text[i]
        if char.isupper():
            result += chr(((a_inv(a) * (ord(char) - b - 65)) % 26) + 65)
        elif char.islower():
            result += chr(((a_inv(a) * (ord(char) - b - 97)) % 26) + 97)
        else:
            result += char
    return result

def a_inv(a):
    for i in range(1, 26):
        if (a*i) % 26 == 1:
            return i
    return None

维吉尼亚密码

加密代码：

def vigenere_cipher(text, key):
    result = ""
    key = key.upper()
    index = 0
    for i in range(len(text)):
        char = text[i]
        if char.isupper():
            result += chr((ord(char) + ord(key[index]) - 130) % 26 + 65)
        elif char.islower():
            result += chr((ord(char) + ord(key[index]) - 194) % 26 + 97)
        else:
            result += char
        if char.isalpha():
            index = (index + 1) % len(key)
    return result

解密代码：

def vigenere_decipher(text, key):
    result = ""
    key = key.upper()
    index = 0
    for i in range(len(text)):
        char = text[i]
        if char.isupper():
            result += chr((ord(char) - ord(key[index]) + 26) % 26 + 65)
        elif char.islower():
            result += chr((ord(char) - ord(key[index]) + 26) % 26 + 97)
        else:
            result += char
        if char.isalpha():
            index = (index + 1) % len(key)
    return result

栅栏密码

加密代码：

def rail_fence_cipher(text, key):
    result = ""
    for i in range(key):
        for j in range(i, len(text), key):
            result += text[j]
    return result

解密代码：

def rail_fence_decipher(text, key):
    result = [""] * len(text)
    index = 0
    for i in range(key):
        j = i
        while j < len(text):
            result[j] = text[index]
            index += 1
            j += key
    return "".join(result)

多倍经典密码

加密代码：

def playfair_cipher(text, key):
    key = key.upper().replace("J", "I")
    text = text.upper().replace("J", "I")
    matrix = create_matrix(key)
    text_pairs = create_text_pairs(text)
    result = ""
    for pair in text_pairs:
        row1, col1 = get_position(matrix, pair[0])
        row2, col2 = get_position(matrix, pair[1])
        if row1 == row2:
            result += matrix[row1][(col1 + 1) % 5] + matrix[row2][(col2 + 1) % 5]
        elif col1 == col2:
            result += matrix[(row1 + 1) % 5][col1] + matrix[(row2 + 1) % 5][col2]
        else:
            result += matrix[row1][col2] + matrix[row2][col1]
    return result

def create_matrix(key):
    key_chars = []
    matrix = []
    for char in key:
        if char not in key_chars:
            key_chars.append(char)
    alphabet = "ABCDEFGHIKLMNOPQRSTUVWXYZ"
    for char in alphabet:
        if char not in key_chars:
            key_chars.append(char)
    for i in range(5):
        matrix.append(key_chars[i*5:(i+1)*5])
    return matrix

def create_text_pairs(text):
    pairs = []
    i = 0
    while i < len(text):
        if i == len(text) - 1:
            pairs.append(text[i] + "X")
            i += 1
        elif text[i] == text[i+1]:
            pairs.append(text[i] + "X")
            i += 1
        else:
            pairs.append(text[i:i+2])
            i += 2
    return pairs

def get_position(matrix, char):
    for i in range(5):
        for j in range(5):
            if matrix[i][j] == char:
                return i, j
    return None

def multi_cipher(text, key):
    result = ""
    for i in range(len(key)):
        shift = ord(key[i]) - 65
        result += caesar_cipher(text, shift)
        text = result
        result = ""
    return text

解密代码：

def playfair_decipher(text, key):
    key = key.upper().replace("J", "I")
    matrix = create_matrix(key)
    text_pairs = create_text_pairs(text)
    result = ""
    for pair in text_pairs:
        row1, col1 = get_position(matrix, pair[0])
        row2, col2 = get_position(matrix, pair[1])
        if row1 == row2:
            result += matrix[row1][(col1 - 1) % 5] + matrix[row2][(col2 - 1) % 5]
        elif col1 == col2:
            result += matrix[(row1 - 1) % 5][col1] + matrix[(row2 - 1) % 5][col2]
        else:
            result += matrix[row1][col2] + matrix[row2][col1]
    return result.replace("X", "") 

def multi_decipher(text, key):
    result = ""
    for i in range(len(key)):
        shift = ord(key[i]) - 65
        result += caesar_decipher(text, shift)
        text = result
        result = ""
    return text