Dart

ECDSA Sign Data and Verify Signature

See more ECC Examples

Demonstrates using the Elliptic Curve Digital Signature Algorithm to hash data and sign it. Also demonstrates how to verify the ECDSA signature. Dart

import 'package:chilkat/chilkat.dart';

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

  // To create an ECDSA signature, the data first needs to be hashed.  Then the hash
  // is signed.

  // Use Chilkat Crypt2 to generate a hash for any of the following
  // hash algorithms: SHA256, SHA384, SHA512, SHA1, MD5, MD2, HAVAL, RIPEMD128/160/256/320

  final crypt = CkCrypt2();
  crypt.hashAlgorithm = 'SHA256';
  crypt.charset = 'utf-8';
  crypt.encodingMode = 'base64';

  // Hash a string.
  final hash1 = crypt.hashStringENC('The quick brown fox jumps over the lazy dog');
  print('hash1 = $hash1');

  // Or hash a file..
  final hash2 = crypt.hashFileENC('qa_data/hamlet.xml');
  print('hash2 = $hash2');

  // (The Crypt2 API provides many other ways to hash data..)

  // -----------------------------------------------------------
  // An ECDSA private key is used for signing.  The public key is for signature verification.
  // Load our ECC private key.
  // Our private key file contains this:

  // 	// -----BEGIN PRIVATE KEY-----
  // 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
  // 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
  // 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
  // 	-----END PRIVATE KEY-----

  final privKey = CkPrivateKey();
  try {
    privKey.loadPemFile('qa_data/ecc/secp256r1-key-pkcs8.pem');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // We'll need a PRNG source for random number generation.
  // Use Chilkat's PRNG (for the Fortuna PRNG algorithm).
  final prng = CkPrng();

  // Sign the hash..
  final ecdsa = CkEcc();
  final String ecdsaSigBase64;
  try {
    ecdsaSigBase64 = ecdsa.signHashENC(hash1, 'base64', privKey, prng);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('ECDSA signature = $ecdsaSigBase64');

  // -----------------------------------------------------------
  // Now let's verify the signature using the public key.

  final pubKey = CkPublicKey();
  try {
    pubKey.loadFromFile('qa_data/ecc/secp256r1-pubkey.pem');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final result = ecdsa.verifyHashENC(hash1, ecdsaSigBase64, 'base64', pubKey);
  if (result == 1) {
    print('Signature is valid.');
    return;
  }

  if (result == 0) {
    print('Signature is invalid.');
    return;
  }

  if (result < 0) {
    print(ecdsa.lastErrorText);
    print('The VerifyHashENC method call failed.');
    return;
  }
}