Polkadot Arkworks Hostcalls

Integration of Arkworks cryptographic primitives as Substrate host functions, demonstrating efficient elliptic curve operations within the Polkadot/Substrate ecosystem.

Overview

This project serves two primary purposes:

1. On-chain Arkworks Demonstration: Shows practical integration of cryptographic operations from the Arkworks ecosystem into Substrate based runtimes through custom pallets and host functions.

2. Arkworks-extensions Backend: Demonstrates how Polkadot SDK host calls can serve as the computational backend for arkworks-extensions, offloading expensive elliptic curve operations from Wasm to native host execution for significant performance improvements.

Features

Pallet Ark Hostcalls (pallet-ark-hostcalls)

Provides cryptographic operations on the Ed-on-BLS12-381-Bandersnatch curve with two curve representations:

Short Weierstrass (SW) Curve Operations:

• ed_on_bls12_381_bandersnatch_msm_sw - Multi-Scalar Multiplication
• ed_on_bls12_381_bandersnatch_mul_projective_sw - Projective scalar multiplication
• ed_on_bls12_381_bandersnatch_mul_affine_sw - Affine scalar multiplication

Twisted Edwards (TE) Curve Operations:

• ed_on_bls12_381_bandersnatch_msm_te - Multi-Scalar Multiplication
• ed_on_bls12_381_bandersnatch_mul_projective_te - Projective scalar multiplication
• ed_on_bls12_381_bandersnatch_mul_affine_te - Affine scalar multiplication

Each operation supports both native Arkworks and Substrate-optimized implementations via the optimized parameter.

Pallet Ark VRF (pallet-ark-vrf)

Implements Verifiable Random Function verification operations using the Bandersnatch suite:

IETF VRF:

• ietf_verify - Verify RFC-compliant VRF proof

Ring-based VRF:

• ring_reset - Initialize ring verifier key builder
• push_members / push_member_buffered - Add ring members
• ring_commit - Finalize ring and build verifier key
• ring_verify - Verify ring-based VRF proof

Configuration options:

• Configurable ring sizes (2^11 with small-ring feature; 2^16 default)
• Pregenerated Universal Reference String (URS) (from zcash ceremony)

Arkworks-Extensions Integration

This project demonstrates how Polkadot SDK host calls can act as a performance-critical backend for the arkworks-extensions library. The integration works as follows:

• Wasm Runtime: Runtime code uses arkworks-extensions API for elliptic curve operations
• Host Call Backend: Expensive operations are dispatched to native host functions (sp-crypto-ec polkadot-sdk crate)
• Performance Gain: Native execution avoids Wasm overhead for computationally intensive cryptographic primitives (MSM, scalar multiplication, etc.)

Project Structure

polkadot-ark-hostcalls/
├── pallets/
│   ├── hostcalls/          # Arkworks cryptographic hostcalls pallet
│   └── vrf/                # VRF verification pallet
├── runtime/                # Substrate based runtime
├── node/                   # Substrate based node
├── benchmark.sh            # Benchmark execution script

Running

Start the Node

cargo run --release -- --dev

Development Mode

cargo run -- --dev --tmp

Benchmarking

The project includes comprehensive benchmarking infrastructure

Examples:

# Benchmark all extrinsics from ark_hostcalls pallet
./benchmark.sh pallet_ark_hostcalls all

# Benchmark substrate based (optimized) VRF verification from ark_vrf pallet
./benchmark.sh pallet_ark_vrf sub_ring_vrf_verify

# Benchmark all extrinsics from ark_vrf pallet
./benchmark.sh pallet_ark_vrf all

Benchmark results are shown in the terminal and stored in the results/ directory.

Feature Flags

• std - Standard library support
• runtime-benchmarks - Enable benchmark implementations
• small-ring - Reduced ring sizes for testing (2^11 instead of 2^16)

Repository

GitHub: davxy/polkadot-arkworks-extensions