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Generate unique, non-sequential keys

October 29th, 2011 · No Comments · Uncategorized

This article demonstrates 3 different methods that I have found to create unique numbers that are non-sequential, do not overlap, and can be modified to produce a non-overlapping series in the future. They are *not* based on random numbers. The encoded series is completely deterministic. Coded in PHP. Hope this helps somebody who’s trying to come up with a numbering scheme that is forward supportable.

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<?php
 
/*
  GetHandleForItemIndex
    Parameters: Integer
 
  Given a series of integers, 
  output a different series that is non-contiguous,
    non-overlapping, and can be modified in the future
    not to overlap numbers that have been generated by
    the same input series.
 
  input 1,2,3,4,5,6,7,8,9,10
  output 8400,35400,62400,89400,116400,143400,170400,197400,224400,251400
 
  By changing the prime number constants, a completly different (and 
    non-overlapping) output series can be generated in the future.
 
  GetItemIndexForHandle
    Parameters: Integer 
 
  Translates the series back into simple decimal contiguous input.
 
*/
 
#const PRIME_NUMBER_A = '65521';
#const PRIME_NUMBER_B = '999721';
#const PRIME_NUMBER_C = '145709';
const PRIME_NUMBER_A = '2';
const PRIME_NUMBER_B = '3';
const PRIME_NUMBER_C = '5';
 
function GetHandleForItemIndex( $in )
{
 
//$in =( PRIME_NUMBER_A*( $in +PRIME_NUMBER_A ) );
$in =bcmul( PRIME_NUMBER_A, bcadd( $in ,PRIME_NUMBER_A ) );
$in =bcmul( PRIME_NUMBER_A, bcsub( $in ,PRIME_NUMBER_B ) );
$in =bcmul( PRIME_NUMBER_A, bcsub( $in ,PRIME_NUMBER_C ) );
$in =bcmul( PRIME_NUMBER_B, bcadd( $in ,PRIME_NUMBER_A ) );
$in =bcmul( PRIME_NUMBER_B, bcsub( $in ,PRIME_NUMBER_B ) );
$in =bcmul( PRIME_NUMBER_B, bcsub( $in ,PRIME_NUMBER_C ) );
$in =bcmul( PRIME_NUMBER_C, bcadd( $in ,PRIME_NUMBER_A ) );
$in =bcmul( PRIME_NUMBER_C, bcsub( $in ,PRIME_NUMBER_B ) );
$in =bcmul( PRIME_NUMBER_C, bcsub( $in ,PRIME_NUMBER_C ) );
return $in;
}
 
function GetItemIndexForHandle( $in )
{
$in = bcadd(bcdiv($in,PRIME_NUMBER_C),PRIME_NUMBER_C);
$in = bcadd(bcdiv($in,PRIME_NUMBER_C),PRIME_NUMBER_B);
$in = bcsub(bcdiv($in,PRIME_NUMBER_C),PRIME_NUMBER_A);
 
$in = bcadd(bcdiv($in,PRIME_NUMBER_B),PRIME_NUMBER_C);
$in = bcadd(bcdiv($in,PRIME_NUMBER_B),PRIME_NUMBER_B);
$in = bcsub(bcdiv($in,PRIME_NUMBER_B),PRIME_NUMBER_A);
 
$in = bcadd(bcdiv($in,PRIME_NUMBER_A),PRIME_NUMBER_C);
$in = bcadd(bcdiv($in,PRIME_NUMBER_A),PRIME_NUMBER_B);
$in = bcsub(bcdiv($in,PRIME_NUMBER_A),PRIME_NUMBER_A);
 
return $in;
 
}
 
?>
 
<HTML>
<HEAD>
<TITLE>Obfuscation Demo</TITLE>
</HEAD>
<BODY>
<TABLE>
<?
for ($i=1;$i<=10;$i++) {
 
  $h =GetHandleForItemIndex($i);
  printf ("<TR><TD>%s</TD><TD>%s</TD></TR>", GetItemIndexForHandle($h), $h) ;
  print "\n";
 
};
 
//print GetHandleForItemIndex('1000000000');
 
 
 
/*
  rot10enc
    Parameters: Integer
 
  Encodes an integer with a simple substitution cipher,
    and then reverses the order of magnitude of the digits.
    The least significant digit is used to reorder an input
    list into non-contiguous, 'unordered' output series.
 
  Input  0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
  Output 6,5,7,4,8,3,9,0,2,1,65,55,75,45,85,35,95
 
  Still somewhat easily predictable, but discourages use
    of the integer for anything other than an identifier.
 
  rot10dec
    Original series is easily retrieved.
 
*/
 
const ROT10 = '6574839021';
const ROT01 = '0123456789';
 
 
function rot10enc($i) {
 
  for ($j=0; $j<strlen($i);$j++) {
    $idx = substr($i,$j,1);
    $buffer .= substr(ROT10,$idx,1);
  }
 
  return strrev($buffer);
 
}
 
function rot10dec($i) {
  $i = strrev($i);
  for ($j=0;$j<strlen($i);$j++) {
    $idx = strpos(ROT10, substr($i,$j,1));
    $buffer .= $idx;
  }
 
  return $buffer;
 
}
 
 
for ($i=0;$i<=10;$i++) {
  $j = rot10enc($i);
  printf ('<TR><TD>%s</TD><TD>%s</TD></TR>', rot10dec($j), $j);
  print "\n";
 
}
 
 
/*
 
  Convert an input integer to any arbitrary base encoding.
    base30 is given as an example.  Note that 3,T,0,O 
    are intentionally missing to illustrate use of this function
    for creating serial numbers that are easily legible.
 
  Also, a base conversion to a nonsense encoding illustrates using
    this algorithm to create a non-contiguous, non-repeating series.
 
  This can be modified to produce non-overlapping series by changing
    either 1) the characters used in the encoding 2) the order of magnitude
    of the input series.
 
INPUT   0,1,2,3,4,5,6,7,8,9,10
OUTPUT  9,A,8,B,7,C,6,D,5,E,4
 
  Further obfuscation is also possible by reversing the order of the
    resulting series digits, so the least significant digit becomes the
    most significant sorting digit.
 
*/
 
 
 
 
const base30a = 'ABCDEFGHJKLMNPQRSUVWXYZ2456789';
const base30x = '9A8B7C6D5E4F2GZHYJXKWLVMUNSPQR';
 
const base62 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
 
const basex = base30x;
const baselen = 30; # 30/62

function dec2base($i) {
 
  while ($i >= strlen(basex)) {
    $base = $i;
    $magnitude = 0;
    while ($base >= baselen) {
      $magnitude++;
      $base /= baselen;
    }
    $idx = intval($base);
    $msd = substr(basex,$idx,1);
    $buffer .= $msd;
    $idx = pow(baselen,$magnitude) * $idx;
    $i -= $idx;
  }
 
  if (strlen($i) <> 0) $buffer .= substr(basex,$i,1);
 
 
  return $buffer;
 
}
 
function base2dec($i) {
 
  while (strlen($i) > 0) {
    $magnitude = strlen($i)-1; #order of magnitude of digit
    $msd = substr($i,0,1);  #the most significant digit itself
    $idx = strpos(basex,$msd) ; #decimal position that digit appears in keyfield
    #add the decimal value of the digit multiplied by it's order of magnitude
    $buffer += pow(baselen,$magnitude) * $idx;  
    $i = substr($i,1); #move on to the next digit
  }
 
  return $buffer;
 
}
 
 
for ($i=0; $i<=10; $i++) {
  $blah = dec2base($i);
  printf ("<TR><TD>%s</TD><TD>%s</TD></TR>\n",$blah, base2dec($blah));
 
}
 
?> 
 
</TABLE>
</BODY>
</HTML>

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