Interfacing a high speed crypto accelerator to an embedded CPU

Crypto coprocessors are needed for acceleration of encryption functions. But critical to the performance gain is the selection of an adequate interface. This paper presents the AES acceleration for two interface options to the LEON CPU core: the CPI interface and the memory-mapped interface. The complete system including the LEON core and the loosely coupled AES accelerators are implemented on an FPGA and the software programs that control the AES accelerators are tested. The cycle count, the throughput, the LUT usage, and the energy cost of running a complete AES program using the above accelerators are compared with a pure software implementation and with a tightly coupled instruction set extension option.