维吉尼亚加密解密Python

以下是Python实现维吉尼亚加密/解密的代码示例：

# 加密函数
def encrypt_vigenere(plaintext, key):
    ciphertext = ""
    key_index = 0
    for char in plaintext:
        if char.isalpha():
            # 将字母转换为0-25的数字
            char_num = ord(char.lower()) - 97
            key_num = ord(key[key_index].lower()) - 97
            # 加密运算
            new_num = (char_num + key_num) % 26
            # 将数字转换为字母
            new_char = chr(new_num + 97)
            ciphertext += new_char
            # 更新密钥索引
            key_index = (key_index + 1) % len(key)
        else:
            ciphertext += char
    return ciphertext

# 解密函数
def decrypt_vigenere(ciphertext, key):
    plaintext = ""
    key_index = 0
    for char in ciphertext:
        if char.isalpha():
            # 将字母转换为0-25的数字
            char_num = ord(char.lower()) - 97
            key_num = ord(key[key_index].lower()) - 97
            # 解密运算
            new_num = (char_num - key_num) % 26
            # 将数字转换为字母
            new_char = chr(new_num + 97)
            plaintext += new_char
            # 更新密钥索引
            key_index = (key_index + 1) % len(key)
        else:
            plaintext += char
    return plaintext

使用示例：

plaintext = "HELLO WORLD"
key = "SECRET"
ciphertext = encrypt_vigenere(plaintext, key)
print(ciphertext) # 输出："DSCWR XHWAH"
decrypted_plaintext = decrypt_vigenere(ciphertext, key)
print(decrypted_plaintext) # 输出："HELLO WORLD"