Encrypted control is a next-generation control technology that provides secure implementation of control algorithms, such as PID controls, to be processed in ciphertext. The secure implementation of the encrypted control is realized by integrating confidential computation (public-key homomorphic encryption schemes) into the computation of control algorithms. As a result, control parameters and communications including sensor measurement and control signals can be kept secret in operating the control system. One of the features of the encrypted control technology is that the control parameters are encrypted, which means the original (unencrypted) control parameters do not need to install to a control unit. Another feature is that the encrypted control system does not need to keep the private key inside a controller unit, so key management costs and the risk of key leakage can be reduced. Moreover, we can use a secure protocol together with the encrypted control technology. Furthermore, we developed "a dynamic-key (key-updatable) encryption scheme" which is a new encryption scheme suitable for encrypted control. The developed makes it possible to update the public and private keys in milliseconds (in place of the key generation process) without running a key-generation algorithm. Therefore, we can construct a more secure control system against cyberattacks such as a replay attack.