Android Open Source - RadaeePDF-B4A P D F A E S Enc

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Back to project page RadaeePDF-B4A.

License

The source code is released under:

Apache License

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Java Source Code

package com.radaee.util;
import java.io.File;
import java.io.FileInputStream;
import java.io.RandomAccessFile;
//from www  . j a v  a 2s  .c o  m
import javax.crypto.*;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

/**
 * encrypt PDF file class.
 * @author radaee
 *
 */
public class PDFAESEnc
{
  static private byte[] process_block( Cipher cipher, byte[] data, int len )
  {
    try
    {
      return cipher.doFinal(data, 0, len);
    }
    catch(Exception e)
    {
      return null;
    }
  }
  static private void write_int(byte[] data, int off, int val)
  {
    data[off + 3] = (byte)(val&0xFF);
    data[off + 2] = (byte)((val>>8)&0xFF);
    data[off + 1] = (byte)((val>>16)&0xFF);
    data[off + 0] = (byte)((val>>24)&0xFF);
  }
  /**
   * encrypt PDF file
   * @param src_file normal PDF file.
   * @param dst_file encrypted PDF file.
   * @param key key to encrypt, must 16 bytes, or 24 bytes, or 32 bytes
   * @return true or false
   */
  static public boolean encrypt( String src_file, String dst_file, byte[] key )
  {
    try
    {
      File ifile = new File(src_file);
      long total = ifile.length();
      int secs_cnt = (int)((total + 4095)/4096);
      byte[] header = new byte[(secs_cnt + 2) * 8];
      header[0] = 'R';
      header[1] = 'D';
      header[2] = 'A';
      header[3] = 'E';
      header[4] = 'S';
      header[5] = 0;
      header[6] = 0;
      header[7] = 0;
      write_int(header, 8, secs_cnt);
      write_int(header, 12, (int)total);

      FileInputStream is = new FileInputStream(new File(src_file));
      File ofile = new File(dst_file);
      ofile.createNewFile();
      RandomAccessFile os = new RandomAccessFile(dst_file, "rw");
      os.write(header);

      SecretKeySpec skey = new SecretKeySpec(key, "AES");  
      Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
      byte[] ivbytes = new byte[]{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
      IvParameterSpec iv = new IvParameterSpec(ivbytes);//need IV in CBC mode
      cipher.init(Cipher.ENCRYPT_MODE, skey, iv);

      byte[] src = new byte[4096];
      int read = 0;
      int header_off = 16;
      int off = header.length;
      while( (read = is.read(src)) > 0 )
      {
        //there are some bytes for padding.
        //so, dst.length always great than src.length.
        byte[] dst = process_block(cipher, src, read);
        os.write(dst);
        int len = dst.length;
        write_int(header, header_off, off);
        write_int(header, header_off + 4, len);
        header_off += 8;
        off += len;
      }
      is.close();
      os.seek(0);
      os.write(header);
      os.close();
      return true;
    }
    catch(Exception e)
    {
      return false;
    }
  }
}

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