ECDSA Signature Verification

Description

This task is an example on how to compute a signature verification using the ECDSA algorithm, the one used in EVM blockchains like Ethereum, Polygon, Hyperledger Besu, Avalanche C-Chain and others. It takes several paramaters as an input, all of them contained in an input.txt file provided as example:

  1. Test string that was signed

  2. Signature with the r, s, v components

  3. Address that signed the message

It will return a boolean indicating if the signature validates correctly.

Using Truebit To Execute ECDSA Verification Example

In order to get a verified result, we can use Truebit to execute the sign-verify task.

The Code

You can find the ECDSA signature verification example within the folder truebit-nextgen-examples/function-tasks/js/ecdsa-sign-verify

📁 src └─📄 ecdsa-verify.js 📁 dist └─main.js 📄 package-lock.json 📄 package.json 📄 rollup.config.mjs

The dist folder and the main.js file are going to be generated after running the npx rollup -c command. More information click here.

Source

ecdsa-verify.js

/*
    Signee address recoverer and validator
    ======================================
    
    This task is an example on how to compute a signature verification using the ECDSA algorithm, the one used in EVM blockchains like Ethereum, Polygon, Hyperledger Besu, Avalanche C-Chain and others. It takes several paramaters as an input, all of them contained in an input.txt file provided as example: 

    Input parameters (input.txt)
    ----------------------------

        A json-formatted file. See the example below:

            {
                "messageHash": "0x13260446136602c31107aa5e08571c276026b60c5156c1a564e268f3ab08492c",
                "signature": {
                    "r": "0x7097b9a0810d13e60182f261708c2c260e86ea09853cd48b184a5a4b4ea08c02",
                    "s": "0x087bd86b8cdee3aec88ac365ec533c9a111e5b5586c4941a790ca46970c3f380",
                    "v": 28
                },
                "address": "0x63f9a92d8d61b48a9fff8d58080425a3012d05c8"
            }
        
        Fields:

            messageHash: "0x" + hex-encoded data (ASCII string, 66 chars).
            signature: ECDSA signature, divided in its 'r', 's' and 'v'
                       components, as specified below.
                r: "0x" + hex-encoded data (ASCII string, 64 chars).
                s: "0x" + hex-encoded data (ASCII string, 64 chars).
                v: numeric parameter.
            address: "0x" + hex-encoded data (ASCII string, 42 chars).

    Output values (output.txt)
    --------------------------

        A JSON-formatted file. See the example below:

            {
                "declaredAddress": "0x63f9a92d8d61b48a9fff8d58080425a3012d05c8",
                "derivedAddress": "0x63f9a92d8d61b48a9fff8d58080425a3012d05c8",
                "match": true
            }
*/

const fs = require('fs');
const elliptic = require('elliptic');
const keccak256 = require('js-sha3').keccak256;
const bn = require('bn.js');

function checkSignature(messageHash, signature, address) {
    const ec = new elliptic.ec('secp256k1');
    const bnHash = new bn(messageHash, 16);
    const recoveryByteV = signature.v - 27;
    const pubKeyRecovered = ec.recoverPubKey(bnHash, signature, recoveryByteV).encode('hex');
    const pubKeyHash = keccak256(Buffer.from(pubKeyRecovered.slice(2), 'hex'));
    const derivedAddress = pubKeyHash.slice(-40);

    return {
        declaredAddress: '0x' + address,
        derivedAddress: '0x' + derivedAddress,
        match: address === derivedAddress
    }
}

function fixHash(input, key) {
    if (typeof input[key] !== 'string') {
        throw (`invalid type on input key '${key}', not a string.`);
    }
    input[key] = input[key].replace('0x', '').toLowerCase();
}


const main = () => {
    const inputJson = fs.readFileSync('input.txt', 'utf-8');
    let inputObj = JSON.parse(inputJson);

    fixHash(inputObj, 'messageHash');
    fixHash(inputObj.signature, 'r');
    fixHash(inputObj.signature, 's');
    fixHash(inputObj, 'address');

    const outputObj = checkSignature(inputObj.messageHash, inputObj.signature, inputObj.address);
    const outputJson = JSON.stringify(outputObj, null, 4);
    fs.writeFileSync('output.txt', outputJson);
    console.log(outputJson);
}

main();

Recommended configuration for Rollup tool (file rollup.config.mjs):

In/Out Parameters

In order to send parameters to the Truebit task, you need to open the "input.txt" file and get the value from there. For now, only one input parameter is allowed.

In order to retrieve the output value from the Truebit task, you need save it in the "output.txt" file.

Try Out

We will use the Truebit CLI to compile and try our source code. Once the code is finished, we will deploy it to the coordination hub so that everyone who knows the namespace and taskname.

Step 1: Create The Ecdsa-Verify Source Code

If you are working in JS, remember to run the Rollup command in order to bundle all the code and dependencies within a single main.js file located at /dist folder.

npx rollup -c

You will find a file called main.js within the folder /dist (This is the file generated by the Rollup tool that will be used for testing purposes).

Step 2: Build The Source Code

Execute the build command against Truebit node to get an instrumented Truebit task.

Output

Step 3: Try The Code

Execute the start command against the Truebit node to test our Algorithm. You will need to submit the instrumented task id + the input parameter.

In this case, the input parameter is a file containing the address, signature and test data that we want to verify. Please use the file called input.txt located within the root folder.

  • [taskId]: Add the taskId generated in the previous step.

Output

Step 4: Deploy The Task

Last, but not least, Execute the deploy command to deploy our task to the coordination hub, so that anyone with the namespace, taskname and the API key can execute it.

  • [taskId]: Add the taskId generated in step 2

Output

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