Dart Requires Chilkat v11.0.0+

Create a JWS Using ECDSA P-256 SHA-256

See more JSON Web Signatures (JWS) Examples

Creates and validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256 Dart

import 'package:chilkat/chilkat.dart';

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

  // Use the following ECC key loaded from JWK format.
  final sbJwk = CkStringBuilder();
  sbJwk.append('{"kty":"EC",');
  sbJwk.append('"crv":"P-256",');
  sbJwk.append('"x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",');
  sbJwk.append('"y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0",');
  sbJwk.append('"d":"jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI"');
  sbJwk.append('}');

  final eccKey = CkPrivateKey();
  // Note: This example loads the ECDSA key from JWK format.  Any format can be loaded
  // into the private key object. (See the online reference documentation..)
  try {
    eccKey.loadJwk(sbJwk.getAsString());
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Create the JWS Protected Header
  final jwsProtHdr = CkJsonObject();
  jwsProtHdr.appendString('alg', 'ES256');

  final jws = CkJws();

  // Set the protected header:
  var signatureIndex = 0;
  jws.setProtectedHeader(signatureIndex, jwsProtHdr);

  // Set the ECC key:
  jws.setPrivateKey(signatureIndex, eccKey);

  // Set the payload.
  final bIncludeBom = false;
  final payloadStr = 'In our village, folks say God crumbles up the old moon into stars.';
  jws.setPayload(payloadStr, 'utf-8', bIncludeBom);

  // Create the JWS
  // By default, the compact serialization is used.
  final String jwsCompact;
  try {
    jwsCompact = jws.createJws();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('JWS: $jwsCompact');

  // Note: ECC signatures use random values, so the output will be different each time a signature is produced.
  // sample output:
  // JWS: eyJhbGciOiJFUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.J6EGTNkeuEjehHHBu0SOKzifm8r35wbx49A5964pxzB7gannyZZPMkK7vmlaPJ-K8Xmm8cZsQySAPC12Xd8avw

  // Now load the JWS, validate, and recover the original text.
  final jws2 = CkJws();

  // Load the JWS.
  jws2.loadJws(jwsCompact);

  final eccPubKey = CkPublicKey();
  eccKey.toPublicKey(eccPubKey);

  // Set the ECC public key used for validation.
  signatureIndex = 0;
  jws2.setPublicKey(signatureIndex, eccPubKey);

  // Validate the 1st (and only) signature at index 0..
  final v = jws2.validate(signatureIndex);
  if (v < 0) {
    // Perhaps Chilkat was not unlocked or the trial expired..
    print('Method call failed for some other reason.');
    print(jws2.lastErrorText);
    return;
  }

  if (v == 0) {
    print('Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.');
    return;
  }

  // If we get here, the signature was validated..
  print('Signature validated.');

  // Recover the original content:
  print(jws2.getPayload('utf-8'));

  // Examine the protected header:
  final joseHeader = CkJsonObject();
  jws2.getProtectedH(signatureIndex, joseHeader);
  joseHeader.emitCompact = false;

  print('Protected (JOSE) header:');
  print(joseHeader.emit());

  // Output:

  // Signature validated.
  // In our village, folks say God crumbles up the old moon into stars.
  // Protected (JOSE) header:
  // { 
  //   "alg": "ES256"
  // }
}