Convert secp256k1 privateKey to ethereum address in dart

privKeyToAddr.dart

import 'dart:typed_data';
import 'package:pointycastle/digests/keccak.dart';
import 'package:pointycastle/ecc/api.dart';
import 'package:pointycastle/ecc/curves/secp256k1.dart';

BigInt decodeToBigInt(List<int> magnitude) {
  BigInt result;

  if (magnitude.length == 1) {
    result = BigInt.from(magnitude[0]);
  } else {
    result = BigInt.from(0);
    for (var i = 0; i < magnitude.length; i++) {
      var item = magnitude[magnitude.length - i - 1];
      result |= (BigInt.from(item) << (8 * i));
    }
  }

  if (result != BigInt.zero) {
    return result.toUnsigned(result.bitLength);
  }
  return BigInt.zero;
}

Uint8List getPubAddressFromPrivKey(Uint8List privBytes) {
  BigInt privKeyInUnsignedInt = decodeToBigInt(privBytes);

  final ECDomainParameters params = ECCurve_secp256k1();
  final publicKey = (params.G * privKeyInUnsignedInt)!;
  Uint8List publicKeyBytes =
      Uint8List.view(publicKey.getEncoded(false).buffer, 1);

  final KeccakDigest keccakDigest = KeccakDigest(256);
  Uint8List hashed = keccakDigest.process(publicKeyBytes);
  return hashed.sublist(12, 32);
}