This book constitutes the proceedings of the 17th International Conference on the Theory and Application of Cryptology and Information Security, ASIACRYPT 2011, held in Seoul, Korea, in December 2011. The 40 revised papers included in this volume were carefully reviewed and selected from 266 submissions. The contributions are organized in topical sections on lattices and quantum cryptography; public key encryption; database privacy; hash function; symmetric key encryption; zero knowledge proof; universal composability; foundation; secure computation and secret sharing; public key signature; and leakage resilient cryptography.