用python语言实现rsa算法

RSA算法是一种非对称加密技术，Python中可以使用内置库`cryptography`来实现RSA。以下是简单的步骤：

1. **安装库**:
首先需要安装`cryptography`库，可以使用pip命令：

   pip install cryptography

2. **生成密钥对**:

   from cryptography.hazmat.primitives import serialization
   from cryptography.hazmat.primitives.asymmetric import rsa

   def generate_keys(key_size=2048):
       private_key = rsa.generate_private_key(public_exponent=65537, key_size=key_size)
       public_key = private_key.public_key()
       return private_key, public_key

   # 使用默认大小生成密钥对
   private_key, public_key = generate_keys()

3. **加密**:

   def encrypt(plaintext, public_key):
       ciphertext = public_key.encrypt(plaintext.encode(), padding.OAEP(
           mgf=padding.MGF1(algorithm=hashes.SHA256()),
           algorithm=hashes.SHA256(),
           label=None
       ))
       return ciphertext

   plaintext = "Hello, RSA!"
   ciphertext = encrypt(plaintext, public_key)

4. **解密**:

   def decrypt(ciphertext, private_key):
       plaintext = private_key.decrypt(ciphertext, padding.OAEP(
           mgf=padding.MGF1(algorithm=hashes.SHA256()),
           algorithm=hashes.SHA256(),
           label=None
       ))
       return plaintext.decode()

   decrypted_text = decrypt(ciphertext, private_key)

5. **保存和加载密钥**:

   def save_key(key_path, key):
       with open(key_path, 'wb') as f:
           pem = key.private_bytes(
               encoding=serialization.Encoding.PEM,
               format=serialization.PrivateFormat.PKCS8,
               encryption_algorithm=serialization.NoEncryption())
           f.write(pem)

   load_key_path = "path/to/private_key.pem"
   save_key(load_key_path, private_key)

   # 加载私钥
   loaded_private_key = serialization.load_pem_private_key(open(load_key_path, 'rb').read(), password=None)