BLST on Arbitrum Stylus

This repo defines a smart contract for Arbitrum Stylus which can verify Ethereum BLS signatures onchain. It uses the heavily optimized and robust BLST project, written in C, compiles it to WebAssembly, and deploys it to the Stylus testnet for use.

Building

Requirements

• Python 3
• Clang 16
• Git
• Rust 1.72 (to use the Stylus CLI tool for deploying your program)

Next, initialize the submodules:

git submodule update --init

Compiling to WASM

make wasm

This will output a bls.wasm file that is ready for an onchain deployment. It runs the file through a Python script that also strips it of some unnecessary information so that an onchain deployment will succeed.

A version of this contract is deployed to the Stylus testnet at address 0x832Dc14b36be855DAA49933E9CEFAd6e4C2Ebb3F. You can interact with it using the cast tool, which is part of the foundry Ethereum toolkit.

export ADDR=0x832Dc14b36be855DAA49933E9CEFAd6e4C2Ebb3F
cast call \
 --rpc-url 'https://stylus-testnet.arbitrum.io/rpc' \
 $ADDR \
 '0xa5acc7f57b7df6ade2b7630e09a925b2ef10fb8c977aa1656b526db0d02b3998055c74f74fc79034678c352ddf531591a388ba9227c6f4d08954d017956b3dd947e5a18a9df064d137417afa8e8809e848af1ad8e47d887820e86a6a50ea0ba001fa422935358c7e0eec86077613406e69953688490437408d08a6995ec57dfccbba0c0f2ce42e8d18359ac0148fc915666f6f626172'

This sends over a BLS public key, followed by a signature, followed by the message being signed as a single hex string. If no output is received, the call was successful.

Compiling to Native

make host

This will produce a main executable in the current directory, which runs the same signature verification code in native mode for your host architecture.

./main a5acc7f57b7df6ade2b7630e09a925b2ef10fb8c977aa1656b526db0d02b3998055c74f74fc79034678c352ddf531591a388ba9227c6f4d08954d017956b3dd947e5a18a9df064d137417afa8e8809e848af1ad8e47d887820e86a6a50ea0ba001fa422935358c7e0eec86077613406e69953688490437408d08a6995ec57dfccbba0c0f2ce42e8d18359ac0148fc915666f6f626172

With the following output:

Public Key: a5acc7f57b7df6ade2b7630e09a925b2ef10fb8c977aa1656b526db0d02b3998055c74f74fc79034678c352ddf531591
Signature: a388ba9227c6f4d08954d017956b3dd947e5a18a9df064d137417afa8e8809e848af1ad8e47d887820e86a6a50ea0ba001fa422935358c7e0eec86077613406e69953688490437408d08a6995ec57dfccbba0c0f2ce42e8d18359ac0148fc915
Message: 666f6f626172
Verified sig

Deploying

The easiest way to deploy your C or C++ program is to use the Cargo Stylus CLI tool, which has a --wasm-file-path flag that accepts arbitrary WASMs.

cargo stylus deploy --wasm-file-path <wasm> --private-key <secret>

Performance & Gas Costs

The gas cost for a single BLST signature verification on Stylus is approximately 17 million gas units. At a basefee of 0.1 gwei, which is what Arbitrum One uses, it amounts to a few dollars of value based on the current price of ETH.

See here for an example tx

If this were priced as a precompile, we estimate it would be ~430k gas units, as the native compilation of BLST uses heavily optimized assembly and SIMD instructions compared to its WASM counterpart. Nonetheless, deploying a program as complex as this to Stylus is far more time efficient than expecting new precompiles to be added to Ethereum chains.

License

The SPDX license identifier for this project is MIT OR Apache-2.0.