This book constitutes the refereed proceedings of the 18th International Conference on the Theory and Application of Cryptology and Information Security Asiacrypt 2012 held in Beijing China in December 2012. The 43 full papers presented were carefully reviewed and selected from 241 submissions. They are organized in topical sections named: public-key cryptography foundation symmetric cipher security proof lattice-based cryptography and number theory hash function cryptographic protocol and implementation issues.