http://www.sciencedirect.com Chaos, Solitons & Fractals Volume 24, Issue 3, May 2005, Pages 775-783 doi:10.1016/j.chaos.2004.09.038This paper describes the security weaknesses of a recently proposed secure communication method based on chaotic masking using projective synchronization of two chaotic systems. We show that the system is insecure and how to break it in two different ways, by high-pass filtering and by generalized synchronization.This work was supported by Ministerio de Ciencia y Tecnologı́a of Spain, research grants TIC2001-0586 and SEG2004-02418, and by the Applied R&D Center, City University of Hong Kong, Hong Kong SAR, China, under Grants no. 9410011 and no. 9620004.Peer reviewed