Designing Secure Unknown Input Observer Using Encryption

 In this paper, a secure unknown input observer is designed in a networked control system environment. For this propose, the Paillier encryption, which is a semi- homomorphic encryption method, is employed. The algebraic calculations required for the estimation can be performed over the encrypted data and the encrypted states estimation are generated. The boundedness condition  of estimation error is obtained by considering the digital processor. This method increases the security of system state estimates and effectively eliminates attacks that disrupt the confidentiality of the data. Simulation on the TE-PCS will be performed to illustrate the results.