  This paper proposes a chaotic map-based multicast scheme for multiuser speech
wireless communication and implements it in an ARM platform. The scheme
compresses the digital audio signal decoded by a sound card and then encrypts
it with a three-level chaotic encryption scheme. First, the position of every
bit of the compressed data is permuted randomly with a pseudo-random number
sequence (PRNS) generated by a 6-D chaotic map. Then, the obtained data are
further permuted in the level of byte with a PRNS generated by a 7-D chaotic
map. Finally, it is operated with a multiround chaotic stream cipher. The whole
system owns the following merits: the redundancy in the original audio file is
reduced effectively and the corresponding unicity distance is increased; the
balancing point between a high security level of the system and real-time
conduction speed is achieved well. In the ARM implementation, the framework of
communication of multicast-multiuser in a subnet and the Internet Group Manage
Protocol is adopted to obtain the function of communication between one client
and other ones. Comprehensive test results were provided to show the
feasibility and security performance of the whole system.
