docs: def encrypt(self, binary, use_sign=True):
          """
          Encrypt binary data.
  
          **中文文档**
  
          - 发送消息时只需要对方的pubkey
          - 如需使用签名, 则双方都需要持有对方的pubkey
          """
          token = rsa.encrypt(binary, self.his_pubkey)  # encrypt it
          if use_sign:
              self.sign = rsa.sign(binary, self.my_privkey, "SHA-1")  # sign it
          return token