String pathToMD5 =
                attachment.getName() + senderLogin + recipientLogin + System.currentTimeMillis();
        MessageDigest m = MessageDigest.getInstance("MD5");

        m.reset();
        m.update(pathToMD5.getBytes());

        byte[] digest = m.digest();
        BigInteger bigInt = new BigInteger(1,digest);
        String hashText = bigInt.toString(16);

        while(hashText.length() < 32 ){
            hashText = '0' + hashText;
        }