(Android™) AES Encrypt and Decrypt a File

Android™ demonstrates how to AES encrypt a file of any size, and then decrypt.

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

    CkCrypt2 crypt = new CkCrypt2();

    crypt.put_CryptAlgorithm("aes");

    // CipherMode may be "ecb" or "cbc"
    crypt.put_CipherMode("cbc");

    // KeyLength may be 128, 192, 256
    crypt.put_KeyLength(256);

    // The padding scheme determines the contents of the bytes
    // that are added to pad the result to a multiple of the
    // encryption algorithm's block size.  AES has a block
    // size of 16 bytes, so encrypted output is always
    // a multiple of 16.
    crypt.put_PaddingScheme(0);

    // An initialization vector is required if using CBC mode.
    // ECB mode does not use an IV.
    // The length of the IV is equal to the algorithm's block size.
    // It is NOT equal to the length of the key.
    String ivHex = "000102030405060708090A0B0C0D0E0F";
    crypt.SetEncodedIV(ivHex,"hex");

    // The secret key must equal the size of the key.  For
    // 256-bit encryption, the binary secret key is 32 bytes.
    // For 128-bit encryption, the binary secret key is 16 bytes.
    String keyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F";
    crypt.SetEncodedKey(keyHex,"hex");

    // Encrypt a file, producing the .aes as output.
    // The input file is unchanged, the output .aes contains the encrypted
    // contents of the input file.

    // Note: The .aes output file has no file format.  It is simply a stream
    // of bytes that resembles random binary data.
    String inFile = "/Users/chilkat/testData/pdf/sample.pdf";
    String outFile = "/Users/chilkat/testData/p7m/sample.pdf.aes";
    boolean success = crypt.CkEncryptFile(inFile,outFile);
    if (success != true) {
        Log.i(TAG, crypt.lastErrorText());
        return;
        }

    // For demonstration purposes, a different instance of the object will be used
    // for decryption.
    CkCrypt2 decrypt = new CkCrypt2();

    // All settings must match to be able to decrypt:
    decrypt.put_CryptAlgorithm("aes");
    decrypt.put_CipherMode("cbc");
    decrypt.put_KeyLength(256);
    decrypt.put_PaddingScheme(0);
    decrypt.SetEncodedIV(ivHex,"hex");
    decrypt.SetEncodedKey(keyHex,"hex");

    // Decrypt the .aes
    inFile = "/Users/chilkat/testData/p7m/sample.pdf.aes";
    outFile = "/Users/chilkat/testData/pdf/recovered.pdf";
    success = decrypt.CkDecryptFile(inFile,outFile);
    if (success == false) {
        Log.i(TAG, decrypt.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."
  }
}