(Android™) RSA Sign Binary Data and Verify (Recover the Original Data)

Demonstrates how to RSA sign binary data and then verify/recover the original data.

Note: This example uses methods introduced in Chilkat v9.5.0.77.

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

    // Load an RSA private key for signing.
    CkPrivateKey privKey = new CkPrivateKey();
    boolean success = privKey.LoadEncryptedPemFile("qa_data/pem/rsa_passwd.pem","passwd");
    if (success != true) {
        Log.i(TAG, privKey.lastErrorText());
        return;
        }

    CkRsa rsa = new CkRsa();
    rsa.ImportPrivateKeyObj(privKey);

    // We have some binary data (in hex) to sign
    String originalData = "0102030405060708090A";
    CkBinData bd = new CkBinData();
    bd.AppendEncoded(originalData,"hex");

    // If successful, the contents of bd are replaced with the RSA signature.
    success = rsa.OpenSslSignBd(bd);
    if (success != true) {
        Log.i(TAG, rsa.lastErrorText());
        return;
        }

    // Show the RSA signature in base64
    Log.i(TAG, bd.getEncoded("base64"));

    // ------------------------------------------
    // Get the public key from the private key
    CkPublicKey pubKey = privKey.GetPublicKey();

    // Verify the signature and extract the original data.
    CkRsa rsa2 = new CkRsa();
    rsa2.ImportPublicKeyObj(pubKey);

    boolean bVerified = rsa2.OpenSslVerifyBd(bd);
    Log.i(TAG, "signature verified: " + String.valueOf(bVerified));

    // Show the original data:
    Log.i(TAG, "original data: " + bd.getEncoded("hex"));


  }

  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."
  }
}