维吉尼亚加密算法python

维吉尼亚加密算法（Vigenère cipher），又称为凯撒密码的一种变体，是一种古典的替换式加密技术，它通过将明文和一个密钥进行位移操作来进行加密。在Python中，你可以使用简单的循环和字母索引来实现维吉尼亚加密。下面是一个基本的Python代码示例：

def vigenere_cipher(plaintext, key):
    encrypted_text = ""
    key_length = len(key)  # Key length is taken as a modulus of the plaintext length if needed

    for i in range(len(plaintext)):
        char = plaintext[i]
        if char.isalpha():  # Only encrypting alphabetic characters
            shift = ord(key[(i % key_length)])  # Shift based on key's position in alphabet
            new_char = chr((ord(char.lower()) + shift - ord('a')) % 26 + ord('a'))
            if char.isupper():
                new_char = new_char.upper()
            encrypted_text += new_char
        else:
            encrypted_text += char

    return encrypted_text

# Example usage
plaintext = "Hello, world!"
key = "secret"
encrypted = vigenere_cipher(plaintext, key)
print(f"Plaintext: {plaintext}\nEncrypted: {encrypted}\n")