Abstract
Chaotic systems have many important properties, such as the sensitive dependence on initial conditions, system parameters, the density of the set of all periodic points and topological transitivity, etc. Most properties are related to some requirements such as mixing and diffusion in the sense of cryptography. Therefore, chaotic cryptosystems have more useful and practical applications. In this paper, a proposed scheme makes use of the chaotic system implemented at the transmitter receiver end as a chaotic multi-key generator producing n chaotic keys to be used by the proposed scheme. This represents important improvements over the Public Key Multi-Message Multi-Recipient Signcryption (PK-MM-MRS) scheme which was published before. Also we introduce a chaotic message mixer at the transmitter receiver end to obtain maximum security.