Overview of RISC-V Scalar Cryptography (Zk) Extension

The RISC-V Scalar Cryptography is a small extension that helps embedded and application processors to reduce code size, reduce the energy consumption and reduce the execution time of cryptographic code. The extension consists of five parts.

• Bit-manipulation instructions for cryptography (Zbkx, Zbkc and Zbkb).
• Zks which defines the instructions relating to the ShangMi Suite. This includes the SM3 hash function and the SM4 block cipher.
• Zkn defines instructions for the NIST Suite cryptographic primitives including AES block cipher and the SHA-2 hash function.
• Zkr defines a CSR for a hardware entropy source. This can be used as a secure source of randomness.
• Zkt specification for constant time execution of specific instructions.

This chapter talks about these parts and how they can be used.

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