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Dehasher script malfunctioning

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Join Date: Sep 2005

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Re: Dehasher script malfunctioning

#21

Sep 28th, 2009

•

Originally Posted by cwarn23

I just discovered that when using ascii_base() on the crc32 hash of 9 and 0 they both end up with blank strings which is a bit of a bug. For now I might try and refine my compression function. I can't really do much to edit your function because it has so many elements I haven't seen before.

You'll get blank strings in some cases. However, if you check the string length, you'll noticed it is comprised of chars. Not all characters in the ASCII table are visible. You however, still have bytes in the string.

However, I've noticed that the function does not work for very large integers due to PHP not being able to do arithmetic on them.

There are some work arounds to this in the comments on:
http://www.php.net/manual/en/function.base-convert.php

If you have bcmath enabled, you can rely on it to do the arithmetic correctly.

Below is the function modified to use BCMath.

 Help with Code Tags 
 PHP Syntax (Toggle Plain Text) 
if (!function_exists('bcdiv')) {
	//echo "No BC Math\n";
	function bcdiv($dividend, $divisor) {
		$quotient = floor($dividend/$divisor);
		return $quotient;
	}
	function bcmod($dividend, $modulo) {
		$remainder = $dividend%$modulo;
		return $remainder;
	}
} else {
	//echo "Using BC Math\n";
}
 
/**
 * Convert Decimal to a base less then 255 comprised of ASCII chars
 *
 * @param Int $num
 * @param Int $base (2-255)
 * @return ASCII String
 */
function base255($num, $base = 255) {
	if ($num < 0) $num = -$num;
	$ret = array();
	while($num > $base) {
		$rem = bcmod($num, $base);
		$num = bcdiv($num, $base);
		$ret[] = chr($rem);
	}
	$ret[] = chr($num);
	return implode('', array_reverse($ret));
}
if (!function_exists('bcdiv')) {
	//echo "No BC Math\n";
	function bcdiv($dividend, $divisor) {
		$quotient = floor($dividend/$divisor);
		return $quotient;
	}
	function bcmod($dividend, $modulo) {
		$remainder = $dividend%$modulo;
		return $remainder;
	}
} else {
	//echo "Using BC Math\n";
}

/**
 * Convert Decimal to a base less then 255 comprised of ASCII chars
 *
 * @param Int $num
 * @param Int $base (2-255)
 * @return ASCII String
 */
function base255($num, $base = 255) {
	if ($num < 0) $num = -$num;
	$ret = array();
	while($num > $base) {
		$rem = bcmod($num, $base);
		$num = bcdiv($num, $base);
		$ret[] = chr($rem);
	}
	$ret[] = chr($num);
	return implode('', array_reverse($ret));
}

I renamed it to base255 so it makes more sense. It should now give you correct values if you have bcmath.

I just profiled the function. It doesn't seem to use much memory at all. Just around 260Kb at the most. I tested both with and without BCMath. Are you sure it isn't something else?

Last edited by digital-ether; Oct 7th, 2009 at 12:19 pm.

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Re: Dehasher script malfunctioning

#22

Sep 28th, 2009

•

Originally Posted by cwarn23

I can't really do much to edit your function because it has so many elements I haven't seen before.

It is actually very basic.

The only odd operations used are:

% - modulo or remainder
chr() - return the character represented by a number in ASCII table
floor() - round down the float to an int

The modulo returns the remainder after dividing

eg: 5%2 = 1
ie: 5/2 = 2 remainder 1

chr(96) = a
The letter a is represented by the number 96 in ASCII

Something like:

$chr = array(96=>'a', 97=>'b' ... 255);
so chr(96) = $chr[96];

And floor just removes everything after the decimal point.

eg: 5/2 = 2.5
floor(2.5) = 2

Here is the function with comments:

 Help with Code Tags 
 PHP Syntax (Toggle Plain Text) 
/**
 * Convert Decimal to a base less then 255 comprised of ASCII chars
 *
 * @param Int $num
 * @param Int $base (2-255)
 * @return ASCII String
 */
function base255($num, $base = 255) {
 	// remove the negative sign by multiplying by -1 if $num is negative
	if ($num < 0) $num = -$num;
	// an array to hold the digits of the new number
	$ret = array();
	// while the number is larger then our base, we just keep dividing it by the base
	while($num > $base) {
		// get the remainder after dividing by the base
		$rem = bcmod($num, $base);
		// divide by the base to move up one unit
		$num = bcdiv($num, $base);
		// the remainders of each division, make up the new number
		// we save the character the remainder represents in ASCII so we only have to save one character, instead of the number
		$ret[] = chr($rem);
	}
	// since the number is less then the base, it is the remainder itself
	$ret[] = chr($num);
	// we reverse the order of chars, since we started calculating remainders from the smallest unit
	return implode('', array_reverse($ret));
}
/**
 * Convert Decimal to a base less then 255 comprised of ASCII chars
 *
 * @param Int $num
 * @param Int $base (2-255)
 * @return ASCII String
 */
function base255($num, $base = 255) {
 	// remove the negative sign by multiplying by -1 if $num is negative
	if ($num < 0) $num = -$num;
	// an array to hold the digits of the new number
	$ret = array();
	// while the number is larger then our base, we just keep dividing it by the base
	while($num > $base) {
		// get the remainder after dividing by the base
		$rem = bcmod($num, $base);
		// divide by the base to move up one unit
		$num = bcdiv($num, $base);
		// the remainders of each division, make up the new number
		// we save the character the remainder represents in ASCII so we only have to save one character, instead of the number
		$ret[] = chr($rem);
	}
	// since the number is less then the base, it is the remainder itself
	$ret[] = chr($num);
	// we reverse the order of chars, since we started calculating remainders from the smallest unit
	return implode('', array_reverse($ret));
}

I think its simplest to look at it when converting base 10 to base 10.

123 would be:

Help with Code Tags

(Toggle Plain Text)

123/10 = 12 R 3
12/10 = 1 R 2
1
---------------
1 R2 R3 or 123

In order to do the first line with PHP:
123/10 = 12 R 3
We need to do:

 Help with Code Tags 
 PHP Syntax (Toggle Plain Text) 
$number = floor(123/10); // 12
$remainder = 123%10; // 3
$number = floor(123/10); // 12
$remainder = 123%10; // 3

I hope that helps.

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Re: Dehasher script malfunctioning

#23

Sep 28th, 2009

I managed to make a better function which doesn't have the gap symbols and is as follows:

 Help with Code Tags 
 php Syntax (Toggle Plain Text) 
function compress_string($string) {
    $str=array();
    $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
    $arr=str_split($string,2);
    while (!empty($arr)) {
        for ($i=0;isset($arr[$i]);$i++) {
            $char=str_split($arr[$i],1);
            unset($arr[$i]);
            $v=($charconvert[$char[0]]*$charconvert[$char[1]])+32;
            if ($v<256) {
                $str[]=chr($v);
                } else {
                $str[]=chr($charconvert[$char[0]]);
                $arr[$i]=$char[1];
                $arr=implode('',$arr);
                }
            }
        }
    return implode('',$str);
    }
function compress_string($string) {
    $str=array();
    $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
    $arr=str_split($string,2);
    while (!empty($arr)) {
        for ($i=0;isset($arr[$i]);$i++) {
            $char=str_split($arr[$i],1);
            unset($arr[$i]);
            $v=($charconvert[$char[0]]*$charconvert[$char[1]])+32;
            if ($v<256) {
                $str[]=chr($v);
                } else {
                $str[]=chr($charconvert[$char[0]]);
                $arr[$i]=$char[1];
                $arr=implode('',$arr);
                }
            }
        }
    return implode('',$str);
    }

The above function I made compresses it to half the size and skips the first 32 characters on the ascii table which are useless to me. I will try this function for a few days and see how it works and hopefully this will be the function.

Try not to bump 10 year old threads as it can be really annoying.
http://syntax.cwarn23.net/
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Re: Dehasher script malfunctioning

#24

Sep 28th, 2009

Previous post Edit:
I discovered my function had a few memory leeks and fixed it to end up being the following:

 Help with Code Tags 
 php Syntax (Toggle Plain Text) 
function compress_string($string) {
    $str=array();
    $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,
    '2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
    $arr=str_split($string,2);
    while (!empty($arr[0]) || $arr[0]===0) {
        for ($i=0;isset($arr[$i]);$i++) {
            $char=str_split($arr[$i],1);
            $arr[$i]='';
            $v=($charconvert[$char[0]]*$charconvert[$char[1]])+32;
            if ($v<256) {
                $str[]=chr($v);
                } else {
                $str[]=$char[0];
                $arr[$i]=$char[1];
                $arrs=implode('',$arr);
                unset($arr);
                $arr=str_split($arrs,2);
                unset($arrs);
                }
            unset($v);
            }
        }
    unset($arr,$char,$charconvert);
    return implode('',$str);
    }
function compress_string($string) {
    $str=array();
    $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,
    '2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
    $arr=str_split($string,2);
    while (!empty($arr[0]) || $arr[0]===0) {
        for ($i=0;isset($arr[$i]);$i++) {
            $char=str_split($arr[$i],1);
            $arr[$i]='';
            $v=($charconvert[$char[0]]*$charconvert[$char[1]])+32;
            if ($v<256) {
                $str[]=chr($v);
                } else {
                $str[]=$char[0];
                $arr[$i]=$char[1];
                $arrs=implode('',$arr);
                unset($arr);
                $arr=str_split($arrs,2);
                unset($arrs);
                }
            unset($v);
            }
        }
    unset($arr,$char,$charconvert);
    return implode('',$str);
    }

Try not to bump 10 year old threads as it can be really annoying.
http://syntax.cwarn23.net/
Smilies: ^_* +_+ v_v -_- *~*`
My favourite PC. - Oopy Doopy Do 2U2!

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Re: Dehasher script malfunctioning

#25

Sep 28th, 2009

•

Originally Posted by cwarn23

Previous post Edit:
I discovered my function had a few memory leeks and fixed it to end up being the following:
Help with Code Tags

php Syntax (Toggle Plain Text)
function compress_string($string) {
    $str=array();
    $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,
    '2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
    $arr=str_split($string,2);
    while (!empty($arr[0]) || $arr[0]===0) {
        for ($i=0;isset($arr[$i]);$i++) {
            $char=str_split($arr[$i],1);
            $arr[$i]='';
            $v=($charconvert[$char[0]]*$charconvert[$char[1]])+32;
            if ($v<256) {
                $str[]=chr($v);
                } else {
                $str[]=$char[0];
                $arr[$i]=$char[1];
                $arrs=implode('',$arr);
                unset($arr);
                $arr=str_split($arrs,2);
                unset($arrs);
                }
            unset($v);
            }
        }
    unset($arr,$char,$charconvert);
    return implode('',$str);
    }
function compress_string($string) { $str=array(); $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7, '2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16); $arr=str_split($string,2); while (!empty($arr[0]) || $arr[0]===0) { for ($i=0;isset($arr[$i]);$i++) { $char=str_split($arr[$i],1); $arr[$i]=''; $v=($charconvert[$char[0]]*$charconvert[$char[1]])+32; if ($v<256) { $str[]=chr($v); } else { $str[]=$char[0]; $arr[$i]=$char[1]; $arrs=implode('',$arr); unset($arr); $arr=str_split($arrs,2); unset($arrs); } unset($v); } } unset($arr,$char,$charconvert); return implode('',$str); }

Multiplication is associative, so you'll get numerous collisions.

 Help with Code Tags 
 PHP Syntax (Toggle Plain Text) 
 $v=($charconvert[$char[0]]*$charconvert[$char[1]])+32;
 $v=($charconvert[$char[0]]*$charconvert[$char[1]])+32;

eg:

 Help with Code Tags 
 PHP Syntax (Toggle Plain Text) 
compress_string('42'); // p
compress_string('24'); // p
compress_string('42'); // p
compress_string('24'); // p

I'm not sure what you're after, so the alternatives I've given are generalizations.

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Re: Dehasher script malfunctioning

#26

Sep 28th, 2009

Thanks for pointing that out but I should be able to code a reader that can filter the incorrect matches. So as you pointed out the string "aecd" would also have the same result as "eadc" but wouldn't "aecd" wouldn't match "aced". Also the normal work around if there were enough symbols is the following line.

 Help with Code Tags 
 PHP Syntax (Toggle Plain Text) 
$v=($charconvert[$char[0]]*$charconvert[$char[1]])+32-$tmp;
$v=($charconvert[$char[0]]*$charconvert[$char[1]])+32-$tmp;

However I have another work around which is when pulling the the data from the database, to rehash the original data and to see if it matches what was requested. An example is as follows:

 Help with Code Tags 
 php Syntax (Toggle Plain Text) 
$_GET['q']=trim($_GET['q']);
        function compress_string($string) {
            $str=array();
            $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
            $arr=str_split($string,2);
            while (!empty($arr[0]) || $arr[0]===0) {
                for ($i=0;isset($arr[$i]);$i++) {
                    $char=str_split($arr[$i],1);
                    $arr[$i]='';
                    if (empty($charconvert[$char[1]])) {
                    $tmp=1; } else {
                    $tmp=$charconvert[$char[1]];
                    }
 
                    $v=($charconvert[$char[0]]*$tmp)+32;
                    if ($v<256) {
                        $str[]=chr($v);
                        } else {
                        $str[]=$char[0];
                        $arr[$i]=$char[1];
                        $arrs=implode('',$arr);
                        unset($arr);
                        $arr=str_split($arrs,2);
                        unset($arrs);
                        }
                    unset($v,$tmp);
                    }
                }
            unset($arr,$char,$charconvert);
            return implode('',$str);
            }
        if ($_GET['hash']>0) {
            $r=mysql_query('SELECT `id` FROM `hash` WHERE `'.$hash.'`="'.mysql_real_escape_string(compress_string($_GET['q'])).'"');
            } else {
            $r=mysql_query('SELECT `id` FROM `hash` WHERE `sha1`="'.mysql_real_escape_string(compress_string(substr($_GET['q'],0,4).hash('crc32',$_GET['q']).hash('crc32b',$_GET['q']))).'"');
            }
        if (mysql_num_rows($r)==0) {
            echo '<table border=0 cellpadding=3 cellspacing=0 bgcolor="#D0D0D0"><tr bgcolor="#D0D0D0"><td bgcolor="#D0D0D0"><b>No Results found for '.htmlentities($_GET['q'],ENT_QUOTES).'</b></td></tr></table>'."\r\n";
            } else {
            echo '<table border=1 cellpadding=2 cellspacing=0 style="border-top:1px; border-top-color:#FFFFFF"><tr bgcolor="#D0D0D0" style="font-family:arial; font-weight:bolder; border-top:1px; border-top-color:#FFFFFF"><td bgcolor="#D0D0D0">Tanslation</td><td bgcolor="#D0D0D0">SHA1</td><td bgcolor="#D0D0D0">Crc32</td><td bgcolor="#D0D0D0">Crc32b</td></tr>'."\r\n";
            while ($data=mysql_fetch_assoc($r)) {
                if ($_GET['q']==hash($hash,$data['id'])) {
                    echo '<tr><td bgcolor="#D0FFFF"><textarea style="width:'.((strlen($data['id'])*10)).'px; height:16px; overflow-y:hidden;" scrolling=no>'.$data['id'].'</textarea></td><td>'.hash('sha1',$data['id']).'</td><td>'.hash('crc32',$data['id']).'</td><td>'.hash('crc32b',$data['id'])."</td></tr>\r\n";
                    }
                }
            echo "</table>\r\n";
            }
$_GET['q']=trim($_GET['q']);
        function compress_string($string) {
            $str=array();
            $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
            $arr=str_split($string,2);
            while (!empty($arr[0]) || $arr[0]===0) {
                for ($i=0;isset($arr[$i]);$i++) {
                    $char=str_split($arr[$i],1);
                    $arr[$i]='';
                    if (empty($charconvert[$char[1]])) {
                    $tmp=1; } else {
                    $tmp=$charconvert[$char[1]];
                    }
                    
                    $v=($charconvert[$char[0]]*$tmp)+32;
                    if ($v<256) {
                        $str[]=chr($v);
                        } else {
                        $str[]=$char[0];
                        $arr[$i]=$char[1];
                        $arrs=implode('',$arr);
                        unset($arr);
                        $arr=str_split($arrs,2);
                        unset($arrs);
                        }
                    unset($v,$tmp);
                    }
                }
            unset($arr,$char,$charconvert);
            return implode('',$str);
            }
        if ($_GET['hash']>0) {
            $r=mysql_query('SELECT `id` FROM `hash` WHERE `'.$hash.'`="'.mysql_real_escape_string(compress_string($_GET['q'])).'"');
            } else {
            $r=mysql_query('SELECT `id` FROM `hash` WHERE `sha1`="'.mysql_real_escape_string(compress_string(substr($_GET['q'],0,4).hash('crc32',$_GET['q']).hash('crc32b',$_GET['q']))).'"');
            }
        if (mysql_num_rows($r)==0) {
            echo '<table border=0 cellpadding=3 cellspacing=0 bgcolor="#D0D0D0"><tr bgcolor="#D0D0D0"><td bgcolor="#D0D0D0"><b>No Results found for '.htmlentities($_GET['q'],ENT_QUOTES).'</b></td></tr></table>'."\r\n";
            } else {
            echo '<table border=1 cellpadding=2 cellspacing=0 style="border-top:1px; border-top-color:#FFFFFF"><tr bgcolor="#D0D0D0" style="font-family:arial; font-weight:bolder; border-top:1px; border-top-color:#FFFFFF"><td bgcolor="#D0D0D0">Tanslation</td><td bgcolor="#D0D0D0">SHA1</td><td bgcolor="#D0D0D0">Crc32</td><td bgcolor="#D0D0D0">Crc32b</td></tr>'."\r\n";
            while ($data=mysql_fetch_assoc($r)) {
                if ($_GET['q']==hash($hash,$data['id'])) {
                    echo '<tr><td bgcolor="#D0FFFF"><textarea style="width:'.((strlen($data['id'])*10)).'px; height:16px; overflow-y:hidden;" scrolling=no>'.$data['id'].'</textarea></td><td>'.hash('sha1',$data['id']).'</td><td>'.hash('crc32',$data['id']).'</td><td>'.hash('crc32b',$data['id'])."</td></tr>\r\n";
                    }
                }
            echo "</table>\r\n";
            }

Also I did a test and for some reason my script does not always suffer from that bug or at least on my test. But I did alter the function a to the following:

 Help with Code Tags 
 php Syntax (Toggle Plain Text) 
function compress_string($string) {
            $str=array();
            $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
            $arr=str_split($string,2);
            while (!empty($arr[0]) || $arr[0]===0) {
                for ($i=0;isset($arr[$i]);$i++) {
                    $char=str_split($arr[$i],1);
                    $arr[$i]='';
                    if (empty($charconvert[$char[1]])) {
                    $tmp=1; } else {
                    $tmp=$charconvert[$char[1]];
                    }
 
                    $v=($charconvert[$char[0]]*$tmp)+32;
                    if ($v<256) {
                        $str[]=chr($v);
                        } else {
                        $str[]=$char[0];
                        $arr[$i]=$char[1];
                        $arrs=implode('',$arr);
                        unset($arr);
                        $arr=str_split($arrs,2);
                        unset($arrs);
                        }
                    unset($v,$tmp);
                    }
                }
            unset($arr,$char,$charconvert);
            return implode('',$str);
            }
function compress_string($string) {
            $str=array();
            $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
            $arr=str_split($string,2);
            while (!empty($arr[0]) || $arr[0]===0) {
                for ($i=0;isset($arr[$i]);$i++) {
                    $char=str_split($arr[$i],1);
                    $arr[$i]='';
                    if (empty($charconvert[$char[1]])) {
                    $tmp=1; } else {
                    $tmp=$charconvert[$char[1]];
                    }
                    
                    $v=($charconvert[$char[0]]*$tmp)+32;
                    if ($v<256) {
                        $str[]=chr($v);
                        } else {
                        $str[]=$char[0];
                        $arr[$i]=$char[1];
                        $arrs=implode('',$arr);
                        unset($arr);
                        $arr=str_split($arrs,2);
                        unset($arrs);
                        }
                    unset($v,$tmp);
                    }
                }
            unset($arr,$char,$charconvert);
            return implode('',$str);
            }

So I guess I'm just lucky that bug doesn't happen on my all the time but still will add that second validator. I also calculated that in 13 days I can fill 30 GB of dehashing data calculating to at least 5 digits. So the script works for my needs even with it's bug of reverse characters having same match. Because mysql can still filter the results from millions of rows to a few dozen it should still do the job.

Try not to bump 10 year old threads as it can be really annoying.
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Re: Dehasher script malfunctioning

#27

Sep 29th, 2009

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Originally Posted by cwarn23

Thanks for pointing that out but I should be able to code a reader that can filter the incorrect matches. So as you pointed out the string "aecd" would also have the same result as "eadc" but wouldn't "aecd" wouldn't match "aced". Also the normal work around if there were enough symbols is the following line.
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PHP Syntax (Toggle Plain Text)
$v=($charconvert[$char[0]]*$charconvert[$char[1]])+32-$tmp;
$v=($charconvert[$char[0]]*$charconvert[$char[1]])+32-$tmp;
However I have another work around which is when pulling the the data from the database, to rehash the original data and to see if it matches what was requested. An example is as follows:
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php Syntax (Toggle Plain Text)
$_GET['q']=trim($_GET['q']);
        function compress_string($string) {
            $str=array();
            $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
            $arr=str_split($string,2);
            while (!empty($arr[0]) || $arr[0]===0) {
                for ($i=0;isset($arr[$i]);$i++) {
                    $char=str_split($arr[$i],1);
                    $arr[$i]='';
                    if (empty($charconvert[$char[1]])) {
                    $tmp=1; } else {
                    $tmp=$charconvert[$char[1]];
                    }
 
                    $v=($charconvert[$char[0]]*$tmp)+32;
                    if ($v<256) {
                        $str[]=chr($v);
                        } else {
                        $str[]=$char[0];
                        $arr[$i]=$char[1];
                        $arrs=implode('',$arr);
                        unset($arr);
                        $arr=str_split($arrs,2);
                        unset($arrs);
                        }
                    unset($v,$tmp);
                    }
                }
            unset($arr,$char,$charconvert);
            return implode('',$str);
            }
        if ($_GET['hash']>0) {
            $r=mysql_query('SELECT `id` FROM `hash` WHERE `'.$hash.'`="'.mysql_real_escape_string(compress_string($_GET['q'])).'"');
            } else {
            $r=mysql_query('SELECT `id` FROM `hash` WHERE `sha1`="'.mysql_real_escape_string(compress_string(substr($_GET['q'],0,4).hash('crc32',$_GET['q']).hash('crc32b',$_GET['q']))).'"');
            }
        if (mysql_num_rows($r)==0) {
            echo '<table border=0 cellpadding=3 cellspacing=0 bgcolor="#D0D0D0"><tr bgcolor="#D0D0D0"><td bgcolor="#D0D0D0"><b>No Results found for '.htmlentities($_GET['q'],ENT_QUOTES).'</b></td></tr></table>'."\r\n";
            } else {
            echo '<table border=1 cellpadding=2 cellspacing=0 style="border-top:1px; border-top-color:#FFFFFF"><tr bgcolor="#D0D0D0" style="font-family:arial; font-weight:bolder; border-top:1px; border-top-color:#FFFFFF"><td bgcolor="#D0D0D0">Tanslation</td><td bgcolor="#D0D0D0">SHA1</td><td bgcolor="#D0D0D0">Crc32</td><td bgcolor="#D0D0D0">Crc32b</td></tr>'."\r\n";
            while ($data=mysql_fetch_assoc($r)) {
                if ($_GET['q']==hash($hash,$data['id'])) {
                    echo '<tr><td bgcolor="#D0FFFF"><textarea style="width:'.((strlen($data['id'])*10)).'px; height:16px; overflow-y:hidden;" scrolling=no>'.$data['id'].'</textarea></td><td>'.hash('sha1',$data['id']).'</td><td>'.hash('crc32',$data['id']).'</td><td>'.hash('crc32b',$data['id'])."</td></tr>\r\n";
                    }
                }
            echo "</table>\r\n";
            }
$_GET['q']=trim($_GET['q']); function compress_string($string) { $str=array(); $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16); $arr=str_split($string,2); while (!empty($arr[0]) || $arr[0]===0) { for ($i=0;isset($arr[$i]);$i++) { $char=str_split($arr[$i],1); $arr[$i]=''; if (empty($charconvert[$char[1]])) { $tmp=1; } else { $tmp=$charconvert[$char[1]]; } $v=($charconvert[$char[0]]*$tmp)+32; if ($v<256) { $str[]=chr($v); } else { $str[]=$char[0]; $arr[$i]=$char[1]; $arrs=implode('',$arr); unset($arr); $arr=str_split($arrs,2); unset($arrs); } unset($v,$tmp); } } unset($arr,$char,$charconvert); return implode('',$str); } if ($_GET['hash']>0) { $r=mysql_query('SELECT `id` FROM `hash` WHERE `'.$hash.'`="'.mysql_real_escape_string(compress_string($_GET['q'])).'"'); } else { $r=mysql_query('SELECT `id` FROM `hash` WHERE `sha1`="'.mysql_real_escape_string(compress_string(substr($_GET['q'],0,4).hash('crc32',$_GET['q']).hash('crc32b',$_GET['q']))).'"'); } if (mysql_num_rows($r)==0) { echo '<table border=0 cellpadding=3 cellspacing=0 bgcolor="#D0D0D0"><tr bgcolor="#D0D0D0"><td bgcolor="#D0D0D0"><b>No Results found for '.htmlentities($_GET['q'],ENT_QUOTES).'</b></td></tr></table>'."\r\n"; } else { echo '<table border=1 cellpadding=2 cellspacing=0 style="border-top:1px; border-top-color:#FFFFFF"><tr bgcolor="#D0D0D0" style="font-family:arial; font-weight:bolder; border-top:1px; border-top-color:#FFFFFF"><td bgcolor="#D0D0D0">Tanslation</td><td bgcolor="#D0D0D0">SHA1</td><td bgcolor="#D0D0D0">Crc32</td><td bgcolor="#D0D0D0">Crc32b</td></tr>'."\r\n"; while ($data=mysql_fetch_assoc($r)) { if ($_GET['q']==hash($hash,$data['id'])) { echo '<tr><td bgcolor="#D0FFFF"><textarea style="width:'.((strlen($data['id'])*10)).'px; height:16px; overflow-y:hidden;" scrolling=no>'.$data['id'].'</textarea></td><td>'.hash('sha1',$data['id']).'</td><td>'.hash('crc32',$data['id']).'</td><td>'.hash('crc32b',$data['id'])."</td></tr>\r\n"; } } echo "</table>\r\n"; }
Also I did a test and for some reason my script does not always suffer from that bug or at least on my test. But I did alter the function a to the following:
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php Syntax (Toggle Plain Text)
function compress_string($string) {
            $str=array();
            $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16);
            $arr=str_split($string,2);
            while (!empty($arr[0]) || $arr[0]===0) {
                for ($i=0;isset($arr[$i]);$i++) {
                    $char=str_split($arr[$i],1);
                    $arr[$i]='';
                    if (empty($charconvert[$char[1]])) {
                    $tmp=1; } else {
                    $tmp=$charconvert[$char[1]];
                    }
 
                    $v=($charconvert[$char[0]]*$tmp)+32;
                    if ($v<256) {
                        $str[]=chr($v);
                        } else {
                        $str[]=$char[0];
                        $arr[$i]=$char[1];
                        $arrs=implode('',$arr);
                        unset($arr);
                        $arr=str_split($arrs,2);
                        unset($arrs);
                        }
                    unset($v,$tmp);
                    }
                }
            unset($arr,$char,$charconvert);
            return implode('',$str);
            }
function compress_string($string) { $str=array(); $charconvert=array('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5,'f'=>6,'1'=>7,'2'=>8,'3'=>9,'4'=>10,'5'=>11,'6'=>12,'7'=>13,'8'=>14,'9'=>15,'0'=>16); $arr=str_split($string,2); while (!empty($arr[0]) || $arr[0]===0) { for ($i=0;isset($arr[$i]);$i++) { $char=str_split($arr[$i],1); $arr[$i]=''; if (empty($charconvert[$char[1]])) { $tmp=1; } else { $tmp=$charconvert[$char[1]]; } $v=($charconvert[$char[0]]*$tmp)+32; if ($v<256) { $str[]=chr($v); } else { $str[]=$char[0]; $arr[$i]=$char[1]; $arrs=implode('',$arr); unset($arr); $arr=str_split($arrs,2); unset($arrs); } unset($v,$tmp); } } unset($arr,$char,$charconvert); return implode('',$str); }
So I guess I'm just lucky that bug doesn't happen on my all the time but still will add that second validator. I also calculated that in 13 days I can fill 30 GB of dehashing data calculating to at least 5 digits. So the script works for my needs even with it's bug of reverse characters having same match. Because mysql can still filter the results from millions of rows to a few dozen it should still do the job.

The reason you don't get duplicates is that a SHA1 is very unique. Thus even with the redundancy introduced by the function, it still does not collide with others.

It is the same as just cutting the SHA1 in half, and keeping the first half. You will will have a low probability of collisions.

So a function like:

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 PHP Syntax (Toggle Plain Text) 
function compress($sha) {
   $parts = str_split($sha, 20);
   return $parts[0];
}
function compress($sha) {
   $parts = str_split($sha, 20);
   return $parts[0];
}

would achieve the same.

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