NYCPHP Meetup

[Gary A. Mort]

     Got an oddball question and since it tracks back to programming for
websites, figured this would be the place to ask: 

  I was wondering if anyone here knows of some standardized lookup tables
for Domain Name Compression. I'm storing a tuple of information to be used
to generate a TOTP token[TOTP key is stored/indexed by Domain Name and
Username it applies to]. Storage limit is, for practical purposes, 64
bytes. 

  If I SHA-1 the data, it comes out nicely at 20 bytes each, which leaves
me 4 bytes to play with. 

  So I've added a format byte for each bit of data...and will think of
something to use that last byte for[probably a rough running counter of the
number of times the data has been accessed/used] 

  For formatting, I'm currently using: x01: SHA-1 x02: Raw Ascii, left
justified x03: Packed Ascii, left justified x04: raw UTF8 x05: reserved to
for some way of packing UTF8 

  With the above format, it means that when possible the data can be stored
in a format where it can be retrieved and reviewed...but if the data is too
long then it sha-1 is the backup so the data can still be USED even if it
can't be queried. 

  Now, I'd like to expand the ability to maintain data in a useful format.
For domains, for example, there are only 316 top level domains at the
moment: http://mandrillapp.com/track/click.php?u=11000867&id=c9a52257db59455f9b94984fbad0f83b&url=http%3A%2F%2Fdata.iana.org%2FTLD%2Ftlds-alpha-by-domain.txt&url_id=765925821&tags=252069,1108865 so some pseodo
code in PHP to handle it could be: 

 $myTLD='com'; if in_array($myTLD, $domains) {
$tldIndex=array_search($myTLD, $domains); // 55 if using the IANA file as
of today // a tld label which is 16 bits long, starting with 1 always uses
table lookup $tldLabel=0xb1000000000000000; // convert the index to a
binary number, as the index does not go above 512 this is limited to at
most 10 bits $tldIndexB=decbin($tldIndex); $tldLabel= $tldLabel| $tldIndexB
} else { // assuming ASCII TLD's here, highest binary value is lowercase z,
decimal 122 // binary 01111010 - ie first bit is ALWAYS 0 $tldLabel =
pack("c*", $myTLD);} }  Note: I'm not actually going through the pain of
decoding/encoding this on the PHP side...it just helps me to think to plot
out the function in PHP and then translate it Javascript and C.  So using
DNS Name Notation
<%0Ahttp://www.tcpipguide.com/free/t_DNSNameNotationandMessageCompressionTechnique-3.htm>
for compression this leads to being able to at encode some longer domains
in a manner which can be reversed for user display. 

  It strikes me that this should be a process done frequently enough that
there is a standard lookup table for common domain label entrees so that
all applications can share it. 

  I realize that the dictionary can be included in with the data, but for
this purpose it doesn't make a lot of since. I can only store and update 3
64 byte chunks, wheras I have available 2k of program space on the chip
<http://www.ti.com/lit/ds/symlink/msp430g2231.pdf>...which should give me
over 1k of space for static lookup storage since the TOTP calculation
function isn't too memory intensive. 

  For the curious, I'm implementing a very simply TOTP keytool on a
Launchpad. Chrome has a nice experimental feature to access the com port on
the computer - so it's child's play to take the existing code snippets and
create a PHP plugin to allow TOTP logons and a supporting Chrome extension
to do auto-detection and entering of the stored passwords. 

  Plus it's a lot of fun figuring out how to merge my love of Website
Engineering with my love of electronics. I'm currently working on a
Javascript and PHP library to fiddle with the IOIO
<https://www.sparkfun.com/products/10585> which is a hell of lot harder
because there I have to figure out his existing protocol and actually
convert the commands into packed byte arrays inside Javascript and PHP. So
far I did some coding at last weeks JoomlaDay and I was only able to get
some one off's done in order to access the thing remotely and toggle the
LED <https://github.com/garyamort/ioioWebsockets/tree/master/oneoffs>.  
For the curious, my actually line count of written code is rather low since
pySerial and pyWebsockets already had most of what I needed.   Now I need
to generate some Javascript and PHP classes to actually use as a library
and use the protocol.  

  Thanks for your time. -Gary
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