(Android™) Validate a JWS Using ECDSA P-521 SHA-512

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

Note: This example requires Chilkat v9.5.0.66 or greater.

Chilkat Android™ Downloads Android™ Java Libraries Android C/C++ Libraries

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // This requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // Note: This example requires Chilkat v9.5.0.66 or greater.

    // 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" 
    //      } 

    CkStringBuilder sbPubKey = new CkStringBuilder();
    sbPubKey.Append("{\"kty\":\"EC\",");
    sbPubKey.Append("\"crv\":\"P-521\",");
    sbPubKey.Append("\"x\":\"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk\",");
    sbPubKey.Append("\"y\":\"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2\"");
    sbPubKey.Append("}");

    CkPublicKey pubKey = new CkPublicKey();
    boolean success = pubKey.LoadFromString(sbPubKey.getAsString());
    if (success != true) {
        Log.i(TAG, pubKey.lastErrorText());
        return;
        }

    CkJws jws = new CkJws();

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

    // Load the JWS.
    CkStringBuilder sbJws = new 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");

    success = jws.LoadJwsSb(sbJws);
    if (success != true) {
        Log.i(TAG, jws.lastErrorText());
        return;
        }

    // Validate the 1st (and only) signature at index 0..
    int v = jws.Validate(signatureIndex);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        Log.i(TAG, "Method call failed for some other reason.");
        Log.i(TAG, jws.lastErrorText());
        return;
        }

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

    // If we get here, the signature was validated..
    Log.i(TAG, "Signature validated.");
    Log.i(TAG, "--");

    // Recover the original content:
    Log.i(TAG, "Recovered content:");
    Log.i(TAG, jws.getPayload("utf-8"));
    Log.i(TAG, "--");

    // Examine the protected header:
    CkJsonObject joseHeader = jws.GetProtectedHeader(signatureIndex);
    if (jws.get_LastMethodSuccess() != true) {
        Log.i(TAG, "No protected header found at the given index.");
        return;
        }

    joseHeader.put_EmitCompact(false);

    Log.i(TAG, "Protected (JOSE) header:");
    Log.i(TAG, joseHeader.emit());

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

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

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}