SIR10US: A tightly coupled elliptic-curve cryptography co-processor for the OpenRISC

Abstract

Today's embedded systems require resource-aware acceleration engines, which support advanced cryptographic algorithms such as elliptic-curve cryptography (ECC). The authors present an application-specific co-processor for digital signature verification according to the Elliptic Curve Digital Signature Algorithm (ECDSA) based on the NIST B-233 standard. A novel OpenRISC-ISA (instruction-set architecture) core featuring a high IPC rate and balanced pipeline stages has been developed to act as the main controlling unit of the accelerator. The redesigned OpenRISC core processes 67% more instructions per second than the reference architecture and ties with a micro-controllable ECC datapath through a highly optimized interface. An ECDSA signature is verified in 11 ms, which is equal to a speedup of 15× and 3.3× with respect to a portable C implementation on the OpenRISC and an assembler-optimized implementation on an ARM7, respectively. Moreover, thanks to a tightly coupled data memory, the proposed co-processor does not block the OpenRISC during its ECC-specific operations, thereby enabling it to also support concurrent execution of other workloads and/or software-based cryptographic extension functions.