(Android™) JWS Using HMAC SHA-256

Creates a JSON Web Signatures (JWS) using HMAC SHA-256.

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.

    boolean success;

    // First create the JWS Protected Header
    CkJsonObject jwsProtHdr = new CkJsonObject();
    jwsProtHdr.AppendString("typ","JWT");
    jwsProtHdr.AppendString("alg","HS256");
    Log.i(TAG, "JWS Protected Header: " + jwsProtHdr.emit());

    // Output:
    // JWS Protected Header: {"typ":"JWT","alg":"HS256"}

    CkJws jws = new CkJws();

    // Set the HMAC key:
    String hmacKey = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow";
    int signatureIndex = 0;
    jws.SetMacKey(signatureIndex,hmacKey,"base64url");

    // Set the protected header:
    jws.SetProtectedHeader(signatureIndex,jwsProtHdr);

    // Set the payload.
    boolean bIncludeBom = false;
    String 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.
    String jwsCompact = jws.createJws();
    if (jws.get_LastMethodSuccess() != true) {
        Log.i(TAG, jws.lastErrorText());
        return;
        }

    Log.i(TAG, "JWS: " + jwsCompact);

    // sample output:
    // JWS: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.bsYsi8HJ0N6OqGI1hKQ9QQRNPxxA5qMpcHLtOvXatk8

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

    // Load the JWS.
    success = jws2.LoadJws(jwsCompact);

    // Set the MAC key used for validation.
    signatureIndex = 0;
    jws2.SetMacKey(signatureIndex,hmacKey,"base64url");

    // Validate the 1st (and only) signature at index 0..
    int v = jws2.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, jws2.lastErrorText());
        return;
        }

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

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

    // Recover the original content:
    Log.i(TAG, jws2.getPayload("utf-8"));

    // Examine the protected header:
    CkJsonObject joseHeader = jws2.GetProtectedHeader(signatureIndex);
    if (jws2.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:

    // 	Signature validated.
    // 	In our village, folks say God crumbles up the old moon into stars.
    // 	Protected (JOSE) header:
    // 	{ 
    // 	  "typ": "JWT",
    // 	  "alg": "HS256"
    // 	} 

  }

  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."
  }
}