Try this out:
<@! start with epoch>
<@ASSIGN secs <@TSTOSECS <@CURRENTTIMESTAMP>>>
<@! add salt>
<@ASSIGN secs "<@RANDOM low=1 high=9>@@secs<@RANDOM low=1 high=9>">
<@! convert to base 26>
<@WHILE expr="@@secs > 26">
<@! shift to ascii for capitals 65-90 convert to char and build code>
<@IF "<@CURROW>%2 = 0">
<@ASSIGN code '<@CHAR <@CALC "abs(@@secs % 26) + 65">>@@code'>
<@ELSE>
<@ASSIGN code '@@code<@CHAR <@CALC "abs(@@secs % 26) + 65">>'>
</@IF>
<@! shift place for base conversion>
<@ASSIGN secs <@CALC "@@secs / 26" precision=0>>
</@WHILE>
Final Code: @@code
DISCLAIMER: It is possible to create the same code if this routine is run
multiple times in the same second. Add a <@SLEEP 1000> to prevent this. Also,
there is an abs() in there because doing modulo on large values produces a
negative value. This is incorrect behavior on Witango's part and something that
I'll need to fix in the server. I do not think it produces a collision problem
in this routine, but it may. It is likely tied to small floating point variable
used in the routine. Oh, and there is also a rounding error that I didn't work
out, but again, it only changed some shift points (26^1 place increases at
unit=13 rather than unit=0). This can removed by floor()ing the base conversion
shift in the final @CALC. Again, I do not believe that this causes a collision
situation. Also, this routine can occasionally create a 7 character code. You
may need to check for and ignore these if you want them all to 8 characters
(This may be able to be eliminated by increasing the LOW value in the first
@RANDOM) Lastly, I don't guarantee this routine. I just whipped it up as a
mental exercise, so you may want to test it out some (see if you get a
collision over a few million iterations), or show it to someone who is good
with algorithms or cryptography.
Robert
-----Original Message-----
From: Roland Dumas [mailto:[email protected]]
Sent: Thursday, October 14, 2010 11:42 AM
To: [email protected]
Subject: Witango-Talk: generating unique codes
looking for method to create unique and non-obvious n-digit codes to be used as
discount codes.
Should be short enough to use as consumer codes (8 digit?), and probably be
something simply to enter, such as an all caps, and not have an easily
discoverable pattern.
I want to generate unique codes and not have to check the history to see if a
code has been used before.
Suggestions?
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