SECRECY IMPROVEMENT IN CONFIDENTIAL COHERENCE MODULATION BY MEANS OF A NEW KEYING STRUCTURE

In this paper, we present a new keying structure which enhances the se crecy of an already relatively secure coherence modulation method we d eveloped recently. The originality of the method consists in using an encrypting key composed of a large amplitude - low frequency part and a low amplitude - high frequency part. These two components ensure tha t the spectrum, as well as the signal tapped by an eavesdropper, are e fficiently corrupted. When the key is applied simultaneously to both t he encoder and the decoder. the signal is correctly restored. Both the oretical aspects and experimental confirmations are presented in this paper. (C) 1998 Elsevier Science B.V. AII rights reserved.