[COLUG] Enterprise Two Factor Authentication

[Jim]

Re http://www.freeauth.org/site/wiki/One%20Time%20Passwords%20with%20PHP, 

consider skipping the hexadecimal characterification of the md5() output. 
I.e., consider changing: 

   $md5 = getOTP64(md5("$i$otphash"));

to 

   $md5 = getOTP64(md5("$i$otphash"),TRUE);

which allows one to remove the hex to integer conversions 
and some of the bit shifting from encode(), simplifying encode(): 

   function encode($j,$nBitsPerEncodedChar,$encoding)
   {
      if (strlen($encoding)!=(1<<$nBitsPerEncodedChar)) {
         echo stderr "strlen(\"$encoding\")!=(1<<$nBitsPerEncodedChar)\n"; 
         exit(EXIT_FAILURE);
      }

      $nBitsInJ=32;
      $encodedJ="";

      /* as long as there are enough bits,
      *  convert $nBitsPerEncodedChar most significant bits
      *  of $nBitsInJ least significant bits of $j
      *  to character from $encoding. */
      HolyMacro

      if ($nBitsInJ>0) { /* pad left over bits with zeros */
         $j&=((1<<$nBitsInJ)-1); /* probably overly paranoid to compensate for ignorance of PHP's bit bucket handling */
         $j      <<=($nBitsPerEncodedChar-$nBitsInJ);
         $nBitsInJ+=($nBitsPerEncodedChar-$nBitsInJ);
      }

      HolyMacro

      return $encodedJ;
   }

or for lsb oriented folks like myself: 

   function encode($j,$nBitsPerEncodedChar,$encoding)
   {
      if (strlen($encoding)!=(1<<$nBitsPerEncodedChar)) {
         echo stderr "strlen(\"$encoding\")!=(1<<$nBitsPerEncodedChar)\n"; 
         exit(EXIT_FAILURE);
      }

      /* Each loop converts $nBitsPerEncodedChar least significant bits of $j
      *  to character from $encoding. */
      $s="";
      for ($n=32;$n>0;$n-=$nBitsPerEncodedChar) {
         $s=$encoding[$j & ((1<<$nBitsPerEncodedChar)-1)].$s;
         $j>>=$nBitsPerEncodedChar;
         $j&=((1<<$n)-1); /* to avoid issue of possible arithmetic shift right filling with 1s */
      }

      return $s;
   }

Only one loop. 
No nesting. 
No cleanup code. 

I like this code much much better.