2011 Workshop on Lightweight Security & Privacy: Devices, Protocols, and Applications Towards an Ultra Lightweight Crypto Processor

Abstract—In this paper, a lightweight processor suitable for lightweight cryptographic applications is presented. The processor instruction set is based on the stack-based ZPU architecture. In addition, a simple generic plug-in interface is implemented in order to allow integration of application specific coprocessors to the main processor core. In the current version of the processor, a simple direct memory access engine and a serialized Klein cipher coprocessor are implemented and connected to the processor core. Through these engines, it is possible to implement various lightweight security and authentication schemes in a code and area effective way. A simple assembler code is written and tested on the processor in order to verify the functionality of the processor core and coprocessors. The code implements a Davies-Meyer coding scheme and uses the Klein block cipher as a hash function. The GCC toolset originally written for the 32-bit ZPU is being adapted to work with the 8-bit processor core. The designed processor is synthesized using VeriSilicon GSMC 0.13um lowpower process high-density standard cell library for a target operating frequency of 100 KHz, and the resultant gate count is 4.5K GE. Keywords-lightweight; cryptographic; ZPU; processor; Klein I