Android™

Verfies an RSA Signature

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Verifies an RSA signature against the original data. Android™

// 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;

    // The following data was signed by the following example:
    // RSA Sign using a Private Key on a USB Token or Smartcard
    CkBinData bd = new CkBinData();
    int i;
    for (i = 0; i <= 100; i++) {
        bd.AppendEncoded("000102030405060708090A0B0C0D0E0F","hex");
        }

    // Load the signature
    CkBinData bdSig = new CkBinData();
    success = bdSig.LoadFile("rsaSignatures/test1.sig");
    if (success == false) {
        Log.i(TAG, "Failed to load the RSA signature");
        return;
        }

    // Get the public key to be used for signature verification.
    CkPublicKey pubKey = new CkPublicKey();
    success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem");
    if (success == false) {
        Log.i(TAG, pubKey.lastErrorText());
        return;
        }

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

    // Verify the hash of the data against the signature.
    // We pass in the original data.  Internally, the hash is generated
    // and used to validate the signature.
    // Validating the RSA signature means two things:  
    // (1) the original data is exactly what was signed, and 
    // (2) it was signed by the owner of the RSA private key.
    success = rsa.VerifyBd(bd,"sha256",bdSig);

    if (success == false) {
        Log.i(TAG, rsa.lastErrorText());
        Log.i(TAG, "Signature invalid.");
        }
    else {
        Log.i(TAG, "Signature valid.");
        }


  }

  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."
  }
}