This chapter is concerned with encryption techniques in the cryptographic sense of the term, that is, techniques designed to ensure the confidentiality of data in general, regardless of its nature. It focuses on homomorphic techniques, in which operations performed on encrypted data are also performed, indirectly, on the underlying clear data. In developing an application, the classic approach is to choose the algorithm with the lowest possible complexity to solve each problem. The best security level reached by current homomorphic schemes is IND-CPA. Several applications have been explored in recent years, combining academic knowledge and industrial. The chapter presents a proof of concept performed on a facial recognition application for biometric authentication. Compression is a major, widely used step in the field of multimedia. Video compression processes typically aim to avoid transmitting redundant information, in order to reduce bandwidth requirements.