This volume constitutes the selected papers of the 15th Annual International Workshop on Selected Areas in Cryptography, SAC 2008, held in Sackeville, New Brunswick, Canada, in August 14-15, 2008. From a total of 99 technical papers, 27 papers were accepted for presentation at the workshop. They cover the following topics: elliptic and hyperelliptic arithmetic, block ciphers, hash functions, mathematical aspects of applied cryptography, stream ciphers cryptanalysis, cryptography with algebraic curves, curve-based primitives in hardware.