Hi,

What do you mean by "adding one more argument to the function for
including a signature"? A signature is created when a hash valus is
encrypted with a private key. It is not part of the hash value. Do you
mean that you want to append some (any) additional data for hashing, in
addition to the one contained in the file?

Btw, when hashing data from streams, you can use the class
'java.security.DigestInputStream' for this. Here's a modded variant of
your function:

  public static char[] calcMD5(String filename) throws Exception
  {
       FileInputStream fis = new FileInputStream(filename);
       MessageDigest md = MessageDigest.getInstance("MD5");

       try {
           DigestInputStream dis = new DigestInputStream(fis, md);
           byte[] buffer = new byte[8192];
           while(dis.read(buffer) != -1)
           ;
       } finally {
           fis.close();
       }

       byte[] bDigest = md.digest();
       char[] cDigest = new char[16];
       for(int i = 0; i < 16; i++)
           cDigest[i] = (char)(bDigest[i] & 0xff);

       return cDigest;
  }

Regards,
Tommy Grändefors
www.pheox.com