In this paper, we give a scheme for synthesizing synchronizing circuits and systems. Synchronization of drive and response system is proved trivially without the need for computing numerically the conditional Lyapunov exponents. We give a definition of the driving and response system having the same functional form, which is more general than the concept of homogeneous driving of Pecora and Carroll [Pecora & Carroll, 1991]. Finally, we show how synchronization coupled with chaos can be used to implement secure communication systems which is inherently error-free in contrast with the signal-masking schemes proposed in [Cuomo & Oppenheim, 1993a,b; Kocarev et al., 1992]