Accelerated Operations with Precompiles (Syscalls)

Ceno provides “precompiles” to accelerate common, computationally intensive operations. These are implemented as syscalls that the guest program can invoke. Using precompiles is much more efficient than executing the equivalent logic in standard RISC-V instructions.

Using Precompiles

To use a precompile, you need to call the corresponding function from the ceno_rt::syscalls module in your guest code.

For example, to compute a Keccak permutation, you can use syscall_keccak_permute:

#![allow(unused)]
fn main() {
use ceno_rt::syscalls::syscall_keccak_permute;

let mut state = [0u64; 25];
// ... initialize state ...
syscall_keccak_permute(&mut state);
}

Available Precompiles

Ceno currently offers the following precompiles:

• Hashing:

  • syscall_keccak_permute: For Keccak-f[1600] permutation, the core of Keccak and SHA-3.
  • syscall_sha256_extend: For the SHA-256 message schedule (W table) extension.

• Cryptography:

  • syscall_secp256k1_add: Elliptic curve addition on secp256k1.
  • syscall_secp256k1_double: Elliptic curve point doubling on secp256k1.
  • syscall_secp256k1_decompress: Decompress a secp256k1 public key.
  • syscall_bn254_add: Elliptic curve addition on BN254.
  • syscall_bn254_double: Elliptic curve point doubling on BN254.
  • syscall_bn254_fp_addmod, syscall_bn254_fp_mulmod: Field arithmetic for BN254’s base field.
  • syscall_bn254_fp2_addmod, syscall_bn254_fp2_mulmod: Field arithmetic for BN254’s quadratic extension field.

You can find examples of how to use each of these syscalls in the examples/ directory of the project.