Patched Crates

Patching a crate refers to replacing the implementation of a specific interface within the crate with a corresponding zkVM precompile, which can achieve significant performance improvements.

Supported Crates

Using Patched Crates

There are two approaches to using patched crates:

Option 1: Directly add the patched crates as dependencies in the guest program's Cargo.toml. For example:

[dependencies]
sha2 = { git = "https://github.com/zkMIPS-patches/RustCrypto-hashes.git", package = "sha2", branch = "patch-sha2-0.10.8" }

Option 2: Add the appropriate patch entries to your guest's Cargo.toml. For example:

[dependencies]
sha2 = "0.10.8"

[patch.crates-io]
sha2 = { git = "https://github.com/zkMIPS-patches/RustCrypto-hashes.git", package = "sha2", branch = "patch-sha2-0.10.8" }

When patching a crate from a GitHub repository rather than crates.io, you need to explicitly declare the source repository in the patch section. For example:

[dependencies]
ed25519-dalek = { git = "https://github.com/dalek-cryptography/curve25519-dalek" }

[patch."https://github.com/dalek-cryptography/curve25519-dalek"]
ed25519-dalek = { git = "https://github.com/zkMIPS-patches/curve25519-dalek", branch = "patch-4.1.3" }

How to Patch a Crate

First, implement the target precompile in zkVM (e.g., syscall_keccak_sponge) with full circuit logic. Given the implementation complexity, we recommend submitting an issue for requested precompiles.

Then replace the target crate's existing implementation with the zkVM precompile (e.g., syscall_keccak_sponge). For example, we have reimplemented keccak256 by syscall_keccak_sponge, and use this implementation to replace keccak256 in the revm crate.

#![allow(unused)]
fn main() {
use zkm_zkvm::lib::keccak256::keccak256 as keccak256_zkvm;

// Define the keccak256 function
#[inline]
pub fn keccak256<T: AsRef<[u8]>>(bytes: T) -> B256 {
    cfg_if::cfg_if! {
        if #[cfg(target_os = "zkvm")] {
            let output = keccak256_zkvm(bytes.as_ref());
            B256::from(output)
        } else {
            keccak256_alloy(bytes)
        }
    }
}
}

Finally, we can use the new keccak256 in the revme guest lib, which the revme guest depends on.