(Android™) RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

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

    CkPrivateKey privKey = new CkPrivateKey();

    // Load the private key from an RSA .key file:
    boolean success = privKey.LoadPemFile("privateKey.key");
    if (success != true) {
        Log.i(TAG, privKey.lastErrorText());
        return;
        }

    String privKeyXml;
    // Get the private key in XML format:
    privKeyXml = privKey.getXml();

    CkRsa rsa = new CkRsa();

    // Import the private key into the RSA component:
    success = rsa.ImportPrivateKey(privKeyXml);
    if (success != true) {
        Log.i(TAG, rsa.lastErrorText());
        return;
        }

    // Create the signature as a hex string:
    rsa.put_EncodingMode("hex");

    String strData = "This is the string to be signed.";

    // Sign the string using the sha-1 hash algorithm.
    // Other valid choices are "md2", "sha256", "sha384",
    // "sha512", and "md5".
    String hexSig = rsa.signStringENC(strData,"sha-1");

    Log.i(TAG, hexSig);

    // Load a digital certificate from a .cer file:
    CkCert cert = new CkCert();

    success = cert.LoadFromFile("myCert.cer");
    if (success != true) {
        Log.i(TAG, cert.lastErrorText());
        return;
        }

    CkPublicKey pubKey;

    pubKey = cert.ExportPublicKey();

    // Now verify using a separate instance of the RSA object:
    CkRsa rsa2 = new CkRsa();

    // Import the public key into the RSA object:
    success = rsa2.ImportPublicKey(pubKey.getXml());
    if (success != true) {
        Log.i(TAG, rsa2.lastErrorText());
        return;
        }

    // The signature is a hex string, so make sure the EncodingMode is correct:
    rsa2.put_EncodingMode("hex");

    // Verify the signature:
    success = rsa2.VerifyStringENC(strData,"sha-1",hexSig);
    if (success != true) {
        Log.i(TAG, rsa2.lastErrorText());
        return;
        }

    Log.i(TAG, "Success.");

  }

  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."
  }
}