This book constitutes the refereed proceedings of the 15th International Conference on Cryptology and Network Security, CANS 2016, held in Milan, Italy, in November 2016. The 30 full papers presented together with 18 short papers and 8 poster papers were carefully reviewed and selected from 116 submissions. The papers are organized in the following topical sections: cryptanalysis of symmetric key; side channel attacks and implementation; lattice-based cryptography, virtual private network; signatures and hash; multi party computation; symmetric cryptography and authentication; system security, functional and homomorphic encryption; information theoretic security; malware and attacks; multi party computation and functional encryption; and network security, privacy, and authentication.