This book constitutes the thoroughly refereed post-conferenceproceedings of the 4th International Conference on Information TheoreticSecurity, held in Shizuoka, Japan, in December 2009.The 13 revised full papers presented together with 6 invited lectureswere carefully reviewed and selected from 50 submissions. The papers areorganized in topical sections on leakage resilient cryptography, quantumcryptography and indistinguishability, connection to computationalsecurity, secret sharing, key agreement from common randomness, randomgraph and group testing, reliable data transmission and computation, aswell as fingerprint and watermarking.