(Android™) RSA Encrypt and Decrypt Strings

Android™ sample code to RSA public-key encrypt and decrypt strings using public and private keys.

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.

    CkRsa rsa = new CkRsa();

    // This example also generates the public and private
    // keys to be used in the RSA encryption.
    // Normally, you would generate a key pair once,
    // and distribute the public key to your partner.
    // Anything encrypted with the public key can be
    // decrypted with the private key.  The reverse is 
    // also true: anything encrypted using the private
    // key can be decrypted using the public key.

    // Generate a 1024-bit key.  Chilkat RSA supports
    // key sizes ranging from 512 bits to 4096 bits.
    boolean success = rsa.GenerateKey(1024);
    if (success != true) {
        Log.i(TAG, rsa.lastErrorText());
        return;
        }

    // Keys are exported in XML format:
    String publicKey = rsa.exportPublicKey();
    String privateKey = rsa.exportPrivateKey();

    String plainText = "Encrypting and decrypting should be easy!";

    // Start with a new RSA object to demonstrate that all we
    // need are the keys previously exported:
    CkRsa rsaEncryptor = new CkRsa();

    // Encrypted output is always binary.  In this case, we want
    // to encode the encrypted bytes in a printable string.
    // Our choices are "hex", "base64", "url", "quoted-printable".
    rsaEncryptor.put_EncodingMode("hex");

    // We'll encrypt with the public key and decrypt with the private
    // key.  It's also possible to do the reverse.
    success = rsaEncryptor.ImportPublicKey(publicKey);

    boolean usePrivateKey = false;
    String encryptedStr = rsaEncryptor.encryptStringENC(plainText,usePrivateKey);
    Log.i(TAG, encryptedStr);

    // Now decrypt:
    CkRsa rsaDecryptor = new CkRsa();

    rsaDecryptor.put_EncodingMode("hex");
    success = rsaDecryptor.ImportPrivateKey(privateKey);

    usePrivateKey = true;
    String decryptedStr = rsaDecryptor.decryptStringENC(encryptedStr,usePrivateKey);

    Log.i(TAG, decryptedStr);

  }

  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."
  }
}