en Research Paper Research Paper In this paper, we propose a new chaos-based communication scheme using the observers. The novelty lies in the masking procedure that is employed to hide the confidential information using the chaotic oscillator. We use a combination of the addition and inclusion methods to mask the information. The performance of two observers, the proportional observer (P-observer) and the proportional integral observer (PI-observer) is compared that are employed as receivers for the proposed communication scheme. We show that the P-observer is not suitable scheme since it imposes unpractical constraints on the messages to be transmitted. On the other hand, we show that the PI-observer is the better solution because it allows greater flexibility in choosing the gains of the observer and does not impose any unpractical restrictions on the message. Chaotic Synchronization,Duffing Oscillator,P & PI-Observers,Secure Communication, 127 139 http://ijeee.iust.ac.ir/browse.php?a_code=A-10-3-68&slc_lang=en&sid=1 R. Kharel 180031947532846001332 180031947532846001332 No K. Busawon 180031947532846001333 180031947532846001333 No Z. Ghassemlooy 180031947532846001334 180031947532846001334 Yes