(Java) Encrypt File in Chunks using AES CBC

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

Chilkat Java Downloads Java Libs for Windows, MacOS, Linux, Alpine Linux, Solaris Java Libs for Android

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // 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) {
        System.out.println("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) {
        System.out.println("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);
    System.out.println("bSame = " + bSame);
  }
}