feat: 添加维吉尼亚加密算法的实现和交互界面

实现维吉尼亚加密和解密功能，包含以下主要功能：
- 支持大小写字母的加密解密
- 提供交互式命令行界面
- 包含加密表显示功能
- 处理非字母字符和空密钥等边界情况

classical-encryption/vigenere_cipher.py

@@ -0,0 +1,150 @@
+import string
+
+
+def _process_vigenere_char(char, key_char, mode):
+    if not char.isalpha():
+        return char
+
+    start = ord('A') if char.isupper() else ord('a')
+    shift = ord(key_char) - ord('A')
+
+    if mode == "encrypt":
+        processed_char_code = (ord(char) - start + shift) % 26 + start
+    elif mode == "decrypt":
+        processed_char_code = (ord(char) - start - shift) % 26 + start
+    else:
+        raise ValueError("无效的模式，必须是 'encrypt' 或 'decrypt'")
+
+    return chr(processed_char_code)
+
+
+def vigenere_encrypt(plaintext, key):
+    """
+    维吉尼亚加密
+    
+    Args:
+        plaintext: 明文字符串
+        key: 密钥字符串
+        
+    Returns:
+        加密后的字符串
+    """
+    processed_key = ''.join(filter(str.isalpha, key.upper()))
+    
+    if not processed_key:
+        raise ValueError("密钥不能为空")
+    
+    ciphertext_chars = []
+    key_length = len(processed_key)
+    key_index = 0
+    
+    for char in plaintext:
+        if char.isalpha():
+            encrypted_char = _process_vigenere_char(char, processed_key[key_index % key_length], "encrypt")
+            ciphertext_chars.append(encrypted_char)
+            key_index += 1
+        else:
+            ciphertext_chars.append(char)
+    
+    return ''.join(ciphertext_chars)
+
+
+def vigenere_decrypt(ciphertext, key):
+    """
+    维吉尼亚解密
+    
+    Args:
+        ciphertext: 密文字符串
+        key: 密钥字符串
+        
+    Returns:
+        解密后的字符串
+    """
+    processed_key = ''.join(filter(str.isalpha, key.upper()))
+    
+    if not processed_key:
+        raise ValueError("密钥不能为空")
+    
+    plaintext_chars = []
+    key_length = len(processed_key)
+    key_index = 0
+    
+    for char in ciphertext:
+        if char.isalpha():
+            decrypted_char = _process_vigenere_char(char, processed_key[key_index % key_length], "decrypt")
+            plaintext_chars.append(decrypted_char)
+            key_index += 1
+        else:
+            plaintext_chars.append(char)
+    
+    return ''.join(plaintext_chars)
+
+
+def display_vigenere_table():
+    """
+    显示维吉尼亚加密表
+    """
+    alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+    
+    print("维吉尼亚加密表:")
+    print("   " + ' '.join(alphabet))
+    print("  +" + "-" * 51)
+    
+    for i, row_start in enumerate(alphabet):
+        row = []
+        for j in range(26):
+            # 计算每个位置的字符
+            char = chr((ord(row_start) - ord('A') + j) % 26 + ord('A'))
+            row.append(char)
+        print(f"{row_start} | {' '.join(row)}")
+    print()
+
+
+def main():
+    """
+    主函数：交互式界面
+    """
+    print("=== 维吉尼亚加密工具 ===")
+    
+    while True:
+        print("\n请选择操作:")
+        print("1. 加密")
+        print("2. 解密")
+        print("3. 显示加密表")
+        print("4. 退出")
+        
+        choice = input("请输入选择 (1-4): ").strip()
+        
+        if choice == '1':
+            plaintext = input("请输入明文: ").strip()
+            key = input("请输入密钥: ").strip()
+            
+            try:
+                ciphertext = vigenere_encrypt(plaintext, key)
+                print(f"加密结果: {ciphertext}")
+            except Exception as e:
+                print(f"加密错误: {e}")
+                
+        elif choice == '2':
+            ciphertext = input("请输入密文: ").strip()
+            key = input("请输入密钥: ").strip()
+            
+            try:
+                plaintext = vigenere_decrypt(ciphertext, key)
+                print(f"解密结果: {plaintext}")
+            except Exception as e:
+                print(f"解密错误: {e}")
+                
+        elif choice == '3':
+            display_vigenere_table()
+            
+        elif choice == '4':
+            print("退出程序。")
+            break
+            
+        else:
+            print("无效选择，请重新输入。")
+
+
+if __name__ == "__main__":
+    main()