维吉尼亚密码python实现

以下是维吉尼亚密码的Python实现：

def encrypt_vigenere(plaintext, key):
    # 将明文和密钥都转换为大写字母
    plaintext = plaintext.upper()
    key = key.upper()

    # 将密钥重复，直到与明文长度相等
    while len(key) < len(plaintext):
        key += key

    # 加密过程
    ciphertext = ""
    for i in range(len(plaintext)):
        char = plaintext[i]
        key_char = key[i]
        if char.isalpha():
            # 计算字符与A的偏移量
            char_offset = ord(char) - ord('A')
            key_offset = ord(key_char) - ord('A')
            # 计算加密后的字符偏移量
            cipher_offset = (char_offset + key_offset) % 26
            # 计算加密后的字符并添加到密文中
            cipher_char = chr(cipher_offset + ord('A'))
            ciphertext += cipher_char
        else:
            # 如果字符不是字母，则直接添加到密文中
            ciphertext += char

    return ciphertext


def decrypt_vigenere(ciphertext, key):
    # 将密文和密钥都转换为大写字母
    ciphertext = ciphertext.upper()
    key = key.upper()

    # 将密钥重复，直到与密文长度相等
    while len(key) < len(ciphertext):
        key += key

    # 解密过程
    plaintext = ""
    for i in range(len(ciphertext)):
        char = ciphertext[i]
        key_char = key[i]
        if char.isalpha():
            # 计算字符与A的偏移量
            char_offset = ord(char) - ord('A')
            key_offset = ord(key_char) - ord('A')
            # 计算解密后的字符偏移量
            plain_offset = (char_offset - key_offset) % 26
            # 计算解密后的字符并添加到明文中
            plain_char = chr(plain_offset + ord('A'))
            plaintext += plain_char
        else:
            # 如果字符不是字母，则直接添加到明文中
            plaintext += char

    return plaintext

使用示例：

plaintext = "HELLO WORLD"
key = "KEY"
ciphertext = encrypt_vigenere(plaintext, key)
print(ciphertext) # "RIJVS UYVJN"

decrypted_plaintext = decrypt_vigenere(ciphertext, key)
print(decrypted_plaintext) # "HELLO WORLD"