recoverPublicKey.js

const dhive = require('@hiveio/dhive');
const { cryptoUtils, Signature } = dhive
const dhiveClient = new dhive.Client(['https://api.hive.blog'], {
  chainId: 'beeab0de00000000000000000000000000000000000000000000000000000000',
})

async function test(){
  let transaction = {
    "ref_block_num":45115,
    "ref_block_prefix":1373329981,
    "expiration":"2021-08-03T12:43:45",
    "operations":[
      ["custom_json",
      {"required_auths":[],"required_posting_auths":["yabapmatt"],"id":"matt-sm_find_match","json":"{\"match_type\":\"Practice\",\"app\":\"matt-steemmonsters/0.6.3\",\"n\":0}"}]
    ],
    "extensions":[],
    "signatures":["1f3eb2cce6b609259a867646198e75a72adafa54434c55f6f54420ec66331b81d5765ea0e8ba5ee4cfbefdda7e45cc5551e51142e2854cc2f3953fd4e14865d9a1"]
  }
  let signature = transaction.signatures[0]
  //transaction must be JSON object
  let publicKey = await recoverKeyFromSignature(transaction, signature)
  console.log(publicKey.toString(), publicKey == 'STM5HCerA3vwtxkejz2PsGWzEkXDrCV46J8bvLX3WGBHdBnN17vnL')
}
test()

async function recoverKeyFromSignature(transaction, signature){
  try {
    let msg = {
      expiration: transaction.expiration,
      extensions: transaction.extensions,
      operations: transaction.operations,
      ref_block_num: transaction.ref_block_num,
      ref_block_prefix: transaction.ref_block_prefix
    };
    //create signature object from string
    let sig = Signature.fromString(signature);
    let digest = cryptoUtils.transactionDigest(msg);
    // Recover public key
    let key = (new Signature(sig.data, sig.recovery)).recover(digest);

    return key;
  } catch (e) {
    console.log(`Error: ${e}`)
  }
}