Android™

Demonstrate RSA Encrypt/Decrypt using BinData

See more RSA Examples

Demonstrates how to RSA encrypt and decrypt data contained in a Chilkat BinData object. 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 RSA public key is used for encryption, and the private key for decryption.

    //  The public key's role is to make encryption accessible to anyone while ensuring that
    //  only the private key holder can decrypt the messages.
    //  The public key is designed to be widely distributed so anyone can use it to encrypt messages
    //  intended for the owner of the private key.

    //  Load our 2048-bit RSA public key.
    CkPublicKey pubKey = new CkPublicKey();
    //  In all Chilkat methods expecting a path, you pass either absolute or relative paths.
    success = pubKey.LoadFromFile("rsaKeys/myTestRsaPublic.pem");
    if (success == false) {
        Log.i(TAG, pubKey.lastErrorText());
        return;
        }

    CkRsa rsa = new CkRsa();

    //  Tell RSA to use the public key.
    rsa.UsePublicKey(pubKey);

    //  RSA encryption is for small amounts of data, on the order of 200 bytes or less.
    //  The maximum number of bytes that can be RSA encrypted depends
    //  on the RSA key size and padding scheme (OAEP padding vs PKCS#1 v1.5 padding).
    //  For specific limits, see: RSA Encryption Maximum Number of Bytes

    //  Create some binary data to encrypt.
    CkBinData bd = new CkBinData();
    int i = 0;
    for (i = 0; i <= 49; i++) {
        bd.AppendByte(i);
        }

    //  Show the bytes to be encrypted in hex format:
    Log.i(TAG, "To be encrypted: " + bd.getEncoded("hex"));

    //  To be encrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

    //  RSA encrypt the contents of the bd, replacing the contents with the RSA encrypted data.
    rsa.EncryptBd(bd,false);

    //  Now it is encrypted.
    Log.i(TAG, "Encrypted size = " + String.valueOf(bd.get_NumBytes()));
    Log.i(TAG, bd.getEncoded("hex"));

    //  Encrypted size = 256
    //  749ED9D0A8767C06C09AD9697F654F86B145F966722F9714902C4175BDBD02E68984ECF111D4D461
    //  EDB4A8E677D399D19CCA60F35C6DE9972F4262880FE9D77DB75915393E8E7DB80AAB5E383013FAEB
    //  60C77D1E6FECC9A7C8426976416C6218FE7DA998EE063CE709E79C240F8625F4A56A0A33AFD63F7A
    //  BA26F2A692B42E878C53B78602C725FE63FF961A46A2B9D436E5E3D9D64AE3F1D1F5AD5F5B47FCD69
    //  447306B77F2FD6D766CCAA1A110A3371586B43DF0D7FFE2220D1B305CF9371AC342F849FB0C90CD99E
    //  C176928D877FE1C0DE1A7CB6EB824FEC7E1DCF90EF2C6BA9F1DFD3EBFBE89C51AF074DC6AE02E544A78
    //  5018C36D3D48B2EF5202AF61AC

    //  ------------------------------------------------------------------------------------------------------------------------
    //  Let's decrypt, which requires the matching private key...

    //  Load the matching 2048-bit RSA private key.
    CkPrivateKey privKey = new CkPrivateKey();
    String password = "secret";
    success = privKey.LoadAnyFormatFile("rsaKeys/myTestRsaPrivate.pem",password);
    if (success == false) {
        Log.i(TAG, privKey.lastErrorText());
        return;
        }

    //  Tell the RSA object to use the private key.
    rsa.UsePrivateKey(privKey);

    //  Decrypt
    success = rsa.DecryptBd(bd,true);
    if (success == false) {
        Log.i(TAG, rsa.lastErrorText());
        return;
        }

    //  Examine the contents of bd to see if it now contains the unencrypted original data.
    Log.i(TAG, "Decrypted: " + bd.getEncoded("hex"));

    //  Decrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

  }

  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."
  }
}