Dart

ECDSA Sign and Verify Data using Different Hash Algorithms

See more ECC Examples

Demonstrates how to create ECDSA signatures on data using different hash algorithms.

Note: This example requires Chilkat v9.5.0.85 or greater because the SignBd and VerifyBd methods were added in v9.5.0.85.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example assumes the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // First load an ECDSA private key to be used for signing.
  final privKey = CkPrivateKey();
  try {
    privKey.loadEncryptedPemFile('qa_data/ecc/secp256r1-key-pkcs8-secret.pem', 'secret');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Load some data to be signed.
  final bd = CkBinData();
  try {
    bd.loadFile('qa_data/hamlet.xml');
  } on ChilkatException {
    print('Failed to load file to be hashed.');
    return;
  }

  final ecdsa = CkEcc();
  final prng = CkPrng();

  // Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
  print('ECDSA signing the sha256 hash of the data...');
  var sig = ecdsa.signBd(bd, 'sha256', 'base64', privKey, prng);
  print('sig = $sig');

  // Verify the signature against the original data.
  // (We must use the same hash algorithm that was used when signing.)

  // Load the public key that corresponds to the private key used for signing.
  final pubKey = CkPublicKey();
  try {
    pubKey.loadFromFile('qa_data/ecc/secp256r1-pub.pem');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final ecc2 = CkEcc();
  var result = ecc2.verifyBd(bd, 'sha256', sig, 'base64', pubKey);
  if (result != 1) {
    print(ecc2.lastErrorText);
    return;
  }

  print('Verified!');

  // ----------------------------------------------------------------------------------------
  // Let's do the same thing, but with sha384 hashing...

  print('--------------------------------------------');
  print('ECDSA signing the sha384 hash of the data...');

  sig = ecdsa.signBd(bd, 'sha384', 'base64', privKey, prng);
  print('sig = $sig');

  result = ecc2.verifyBd(bd, 'sha384', sig, 'base64', pubKey);
  if (result != 1) {
    print(ecc2.lastErrorText);
    return;
  }

  print('Verified!');
}