Efficient Pointwise and Blockwise Encrypted Operations

Signal processing tools working directly on encrypted data could provide an efficient solution to application scenarios where sensitive signals must be protected from an untrusted processing device. In this paper, we investigate an issue usu-ally neglected in the proposed solutions for secure processing in the encrypted domain, that is the data expansion from the plaintext to the encrypted representation of signals, due to the use of cryptosystems operating on very large algebraic structures. A packed signal representation is proposed that allows to speed up pointwise operations on encrypted signal via parallel processing and to reduce the size of the whole encrypted signal