Non-interactive Evaluation of Encrypted Elementary Functions

Liang Chen, Chengmin Gao, Yong Xu

Abstract: Mobile code can be considered composing of functions. Sander et al implemented non-interactive evaluation of encrypted functions(non-interactive EEF) based on homomorphism. But their scheme is limited to encrypting polynomials in positive integer domain. There is no homomorphism that can securely implement non-interactive evaluation of encrypted elementary functions (non-interactive EEEF) in real domain now. In this paper, addition and multiplication homomorphism in real domain based on a modified ElGamal are proposed. Then using Taylor series we expand elementary functions approximately into polynomials, which can be encrypted and computed by the proposed homomorphism non-interactively. Then we implement non-interactive EEEF in real domain.