This book constitutes the proceedings of the 10th International Workshop on Security, IWSEC 2015, held in Nara, Japan, in August 2015. The 18 full papers and 3 short papers presented in this volume were carefully reviewed and selected from 58 submissions. They were organized in topical sections named: identity-based encryption; elliptic curve cryptography; factoring; symmetric cryptanalysis; provable security; LWE-based encryption; privacy-preserving and anonymity; secure protocol; systems security; and security in hardware.