Solana: How to directly verify ed25519 signatures in a contract

Verifying Ed25519 Signatures Directly in a Solana Contract

As blockchain developers, we often face the challenge of integrating various signing mechanisms into our contracts. One such mechanism is ed25519, which allows for secure and efficient digital signatures using a cryptographic hash function and a private key. While there are existing solutions that enable verifying ed25519 signatures indirectly, placing the signature instruction and the calling instruction in a single transaction can be cumbersome.

In this article, we will explore an alternative approach to directly verify ed25519 signatures in a Solana contract.

The Problem

Before diving into the solution, let’s address some common concerns:

• Transaction size: Directly verifying ed25519 signatures requires a significant amount of storage space. By placing the signature instruction and calling instruction in a single transaction, we risk exceeding the maximum transaction size limit.

• Performance overhead: Verifying each signature individually can introduce additional latency, which might not be acceptable for high-frequency trading or real-time applications.

The Solution

To address these concerns, we will implement a custom solution that uses the verify instruction to verify ed25519 signatures directly. This approach requires careful consideration of the following aspects:

Signature Verification Functionality

We will create a dedicated function within our contract that verifies ed25519 signatures. This function will take the signature input and the hash of the contract’s storage as arguments.

pragma solidity ^0.8.0;


contract SignatureVerifier {

    // ... (other variables)


    function verifyEd25519Signature(

        bytes32 _signature,

        address _from,

        bytes memory _storageHash,

        uint256 _gasLimit

    ) public view returns (bool) {

        // Verify the signature using ed25519

        require ed25519Verify(_signature, _from, _storageHash, _gasLimit);

        return true;

    }

}

ed25519 Library Integration

We will use the solana-verify library to perform the actual verification. This library provides a high-level interface for verifying signatures using ed25519.

pragma solidity ^0.8.0;


library solanaVerify {

    function verify(uint256 _hash) internal view returns (bool);

}


contract SignatureVerifier {

    using solanaVerify.sol(solanaVerify);


    // ... (other variables)


    function verifyEd25519Signature(

        bytes32 _signature,

        address _from,

        bytes memory _storageHash

    ) public view returns (bool) {

        return verify(_signature, _from, _storageHash);

    }

}

Transaction Structure

To avoid exceeding the maximum transaction size limit, we will structure our contract as follows:

pragma solidity ^0.8.0;


contract SignatureVerifier {

    // ... (other variables)


    bytes32 public signature;

    address public from;

    bytes memory storageHash;


    function setSignature(bytes32 _signature) public {

        require ed25519Verify(_signature, from, storageHash, 100000); // 100k gas

        signature = _signature;

        from = address(...);

        storageHash = _storageHash;

    }


    function verifyEd25519Signature(

        bytes32 _signature,

        address _from,

        bytes memory _storageHash

    ) public view returns (bool) {

        require ed25519Verify(_signature, _from, _storageHash, 100000); // 100k gas

        return true;

    }

}

Example Usage

To use this solution, create a new contract and import the SignatureVerifier contract.

“`sol

pragma solidity ^0.8.