Solved

signed / unsigned integer problem

Posted on 2003-10-25
1
152 Views
Last Modified: 2008-02-01
I have a function in C++:

    int gg_login_hash(char *password, int seed) {
            unsigned int x, y, z;

            y = seed;

            for (x = 0; *password; password++) {
                    x = (x & 0xffffff00) | *password;
                    y ^= x;
                    y += x;
                    x <<= 8;
                    y ^= x;
                    x <<= 8;
                    y -= x;
                    x <<= 8;
                    y ^= x;

                    z = y & 0x1f;
                    y = (y << z) | (y >> (32 - z));
          }
          return y;
    }
   
... and i have converted it to PHP:

    function ggLoginHash($password, $seed) {
   
        $y = $seed;
        $x = 0;
        for ($nr = 0, $length = strlen($password); $nr < $length; $nr++) {
            $x = ($x & 0xFFFFFF00) | ord($password[$nr]);
            $y ^= $x;
            $y += $x;
            $x <<= 8;
            $y ^= $x;
            $x <<= 8;
            $y -= $x;
            $x <<= 8;
            $y ^= $x;
           
            $z = $y & 0x1F;
            $y = ($y << $z) | ($y >> (32 - $z));
        }
        return $y;
    }

The problem is that it doesn't realy seem to return the same value.
I think the problem is that there are variables in the C++ code marked as unsigned int, which i can not do in PHP.
Can someone help me converting that so it will work correctly?

Example:
Calling code from C++:
gg_login_hash("dupa", 128) gives 1453413288 in a result.
0
Comment
Question by:Lukasz Lach
1 Comment
 
LVL 14

Accepted Solution

by:
ThG earned 125 total points
ID: 9621561

Hmm, /me thinks.
From a quick debug looks like the $y >> (32 - $z) is performing an aritmetic shift right rather than a logical shift right, as it does (and should do) in C.
This made me think a little so i decided to check the PHP manual for the bitwise operators and in fact a comment points out that all the shift operations are signed (thus aritmetical). Very bad!

So here is a hackish workaround to clean the sign and complete the shifting:
 ...
            $z = $y & 0x1F;
            $y1 = ($y << $z);
            $y2 = 0;
            if ($z < 32) {
              $y2 = $y >> 1;
              $y2 &= 0x7fffffff;
              $y2 = $y2 >> (31 - $z);
            }
            $y = $y1 | $y2;
 ...

I'm the best PHP coder ;-)
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Password hashing is better than message digests or encryption, and you should be using it instead of message digests or encryption.  Find out why and how in this article, which supplements the original article on PHP Client Registration, Login, Logo…
This article discusses how to create an extensible mechanism for linked drop downs.
This tutorial will teach you the core code needed to finalize the addition of a watermark to your image. The viewer will use a small PHP class to learn and create a watermark.
The viewer will learn how to create a basic form using some HTML5 and PHP for later processing. Set up your basic HTML file. Open your form tag and set the method and action attributes.: (CODE) Set up your first few inputs one for the name and …

863 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

18 Experts available now in Live!

Get 1:1 Help Now