Simple XOR applied to first 512 bytes

ImageCrypto.java

import java.io.*;

public class ImageCrypto {

  private static final int XOR_KEY = 345;
  private static final int BYTE_LENGTH = 512;
  
  public static void applyXor( File file ) throws IOException  {
    RandomAccessFile rac = new RandomAccessFile(file, "rw");
    byte[] data = new byte[BYTE_LENGTH];
	
    rac.read( data );
    byte[] newData = xor( data );
    rac.seek(0);
    rac.write(newData);
    rac.close();
  }
  
  public static byte[] xor( byte[] data ) {
    byte[] newData = new byte[data.length];

    for (int i = 0; i < data.length; i++) {
      newData[i] = xor(data[i]);
    }

    return newData;
  }

  public static byte xor(byte b) {
    return (byte) (0xFF & ((int) b ^ XOR_KEY));
  }

}