(Android™) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

Note: This example requires Chilkat v11.0.0 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);

    boolean success = false;

    // 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 PEM file:
    success = privKey.LoadAnyFormatFile("raul_privateKey.key","a0123456789");
    if (success == false) {
        Log.i(TAG, privKey.lastErrorText());
        return;
        }

    CkRsa rsa = new CkRsa();

    // Import the private key into the RSA component:
    success = rsa.UsePrivateKey(privKey);
    if (success == false) {
        Log.i(TAG, rsa.lastErrorText());
        return;
        }

    // This example will sign a string, and receive the signature
    // in a hex-encoded string.  Therefore, set the encoding mode
    // to "hex":
    rsa.put_EncodingMode("hex");

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

    // Sign the string using the sha256 hash algorithm.
    // Other valid choices are sha1, sha384, sha512 and others.
    String hexSig = rsa.signStringENC(strData,"sha256");
    if (rsa.get_LastMethodSuccess() == false) {
        Log.i(TAG, rsa.lastErrorText());
        return;
        }

    Log.i(TAG, hexSig);

    // Now verify with the public key.
    // This example shows how to use the public key from 
    // a digital certificate (.cer file)
    CkCert cert = new CkCert();
    success = cert.LoadFromFile("raul_publicKey.cer");
    if (success == false) {
        Log.i(TAG, cert.lastErrorText());
        return;
        }

    CkPublicKey pubKey = new CkPublicKey();
    cert.GetPublicKey(pubKey);

    CkRsa rsa2 = new CkRsa();
    success = rsa2.UsePublicKey(pubKey);
    if (success == false) {
        Log.i(TAG, rsa2.lastErrorText());
        return;
        }

    // Verify the signature against the original data:
    rsa2.put_EncodingMode("hex");
    success = rsa2.VerifyStringENC(strData,"sha256",hexSig);
    if (success == false) {
        Log.i(TAG, rsa2.lastErrorText());
        return;
        }

    Log.i(TAG, "Signature verified!");

    // Verify with incorrect data:
    success = rsa2.VerifyStringENC("something else","sha256",hexSig);
    if (success != true) {
        Log.i(TAG, "Signature not verified! (which was expected in this case)");
        }
    else {
        Log.i(TAG, "Hmmm... that's not right...");
        }


  }

  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."
  }
}