This book constitutes the proceedings of the 2th International Workshop on Lightweight Cryptography for Security and Privacy LightSec 2013 held in Gebze Turkey during May 6-7 2013. The 10 full papers presented together with 3 invited talks were carefully reviewed and selected from 27 submissions. The papers are grouped in topical sections on efficient Implementations and designs block cipher cryptanalysis wireless sensor networks and cryptographic protocols.