Dart Requires Chilkat v11.0.0+

Validate a JWS Using ECDSA P-521 SHA-512

See more JSON Web Signatures (JWS) Examples

Validates a JSON Web Signature (JWS) that uses ECDSA P-521 SHA-512 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.

  // This example takes a JSON signature in compact serialization format,
  // and uses an ECDSA public key to validate and recover the protected header and payload.

  // We only need a public key for signature validation.  This is the ECDSA public key
  // that is used:

  //      {"kty":"EC", 
  //       "crv":"P-521", 
  //       "x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk", 
  //       "y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2" 
  //      } 

  final sbPubKey = CkStringBuilder();
  sbPubKey.append('{"kty":"EC",');
  sbPubKey.append('"crv":"P-521",');
  sbPubKey.append('"x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk",');
  sbPubKey.append('"y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2"');
  sbPubKey.append('}');

  final pubKey = CkPublicKey();
  try {
    pubKey.loadFromString(sbPubKey.getAsString());
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final jws = CkJws();

  // Set the ECC public key:
  final signatureIndex = 0;
  jws.setPublicKey(signatureIndex, pubKey);

  // Load the JWS.
  final sbJws = CkStringBuilder();
  sbJws.append('eyJhbGciOiJFUzUxMiJ9');
  sbJws.append('.');
  sbJws.append('UGF5bG9hZA');
  sbJws.append('.');
  sbJws.append('AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq');
  sbJws.append('wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp');
  sbJws.append('EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn');

  try {
    jws.loadJwsSb(sbJws);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

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

  // Examine the protected header:

  final joseHeader = CkJsonObject();
  try {
    jws.getProtectedH(signatureIndex, joseHeader);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  joseHeader.emitCompact = false;

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

  // Output:
  // (the string "Payload" was the content that was signed.)

  // 	Signature validated.
  // 	--
  // 	Recovered content:
  // 	Payload
  // 	--
  // 	Protected (JOSE) header:
  // 	{
  // 	  "alg": "ES512"
  // 	}
}