(Android™) Encrypt File in Chunks using AES CBC

Demonstrates how to use the FirstChunk/LastChunk properties to encrypt a file chunk-by-chunk.

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.

    CkCrypt2 crypt = new CkCrypt2();

    crypt.put_CryptAlgorithm("aes");
    crypt.put_CipherMode("cbc");
    crypt.put_KeyLength(128);

    crypt.SetEncodedKey("000102030405060708090A0B0C0D0E0F","hex");
    crypt.SetEncodedIV("000102030405060708090A0B0C0D0E0F","hex");

    String fileToEncrypt = "qa_data/hamlet.xml";
    CkFileAccess facIn = new CkFileAccess();
    boolean success = facIn.OpenForRead(fileToEncrypt);
    if (success != true) {
        Log.i(TAG, "Failed to open file that is to be encrytped.");
        return;
        }

    String outputEncryptedFile = "qa_output/hamlet.enc";
    CkFileAccess facOutEnc = new CkFileAccess();
    success = facOutEnc.OpenForWrite(outputEncryptedFile);
    if (success != true) {
        Log.i(TAG, "Failed to encrypted output file.");
        return;
        }

    // Let's encrypt in 10000 byte chunks.
    int chunkSize = 10000;
    int numChunks = facIn.GetNumBlocks(chunkSize);

    crypt.put_FirstChunk(true);
    crypt.put_LastChunk(false);

    CkBinData bd = new CkBinData();

    int i = 0;
    while (i < numChunks) {
        i = i + 1;
        if (i == numChunks) {
            crypt.put_LastChunk(true);
            }

        // Read the next chunk from the file.
        // The last chunk will be whatever amount remains in the file..
        bd.Clear();
        facIn.FileReadBd(chunkSize,bd);

        // Encrypt.
        crypt.EncryptBd(bd);

        // Write the encrypted chunk to the output file.
        facOutEnc.FileWriteBd(bd,0,0);

        crypt.put_FirstChunk(false);
        }

    // Make sure both FirstChunk and LastChunk are restored to true after
    // encrypting or decrypting in chunks.  Otherwise subsequent encryptions/decryptions
    // will produce unexpected results.
    crypt.put_FirstChunk(true);
    crypt.put_LastChunk(true);

    facIn.FileClose();
    facOutEnc.FileClose();

    // Decrypt the encrypted output file in a single call using CBC mode:
    String decryptedFile = "qa_output/hamlet_dec.xml";
    success = crypt.CkDecryptFile(outputEncryptedFile,decryptedFile);
    // Assume success for the example..

    // Compare the contents of the decrypted file with the original file:
    boolean bSame = facIn.FileContentsEqual(fileToEncrypt,decryptedFile);
    Log.i(TAG, "bSame = " + String.valueOf(bSame));

  }

  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."
  }
}