Despite being proposed since more than 50 years ago, COordinate Rotation DIgital Computer (CORDIC) is still one of the most effective algorithms for elementary function calculation so far. Original CORDIC, however, suffers high latency due to its nature of unvarying number of rotations. As a result, a low-latency hybrid adaptive (HA) CORDIC is proposed in this paper. Firstly, adaptive angle selection decreases total iterations up to 50% with respect to higher accuracy of results. Secondly, hybrid architecture including fixed-point input and floating-point output reduces the total hardware utilization and enhances the dynamic range of final results. Lastly, parallel and pipeline processing together with resource sharing technique allow the design to operate fully at 175.7 MHz with low resource consumption -1,139 LUTs and 489 registers.
The Trusted Execution Environment (TEE) offers a software platform for secure applications. The TEE offers a memory isolation scheme and software authentication from a high privilege mode. The procedure uses different algorithms such as hashes and signatures, to authenticate the application to secure. Although the TEE hardware has been defined for memory isolation, the security algorithms often are executed using software implementations. In this paper, a RISC-V system compatible with TEEs featuring security algorithm accelerators is presented. The hardware accelerators are the SHA-3 hash and the Ed25519 elliptic curve algorithms. TileLink is used for the communications between the processor and the register of the accelerators. For the TEE boot, the software procedures are switched with the accelerated counterpart. Comparing to the software approach, a 2.5-decade increment is observed in the throughput of the signature procedure using the SHA-3 acceleration for big chunks of data. The Ed25519 performs 90% better compared to the software counterpart in execution times.
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