encryption with python

Mike Meyer mwm at mired.org
Fri Sep 9 23:08:38 CEST 2005

Steven D'Aprano <steve at REMOVETHIScyber.com.au> writes:
> On Wed, 07 Sep 2005 14:31:03 -0700, jlocc wrote:
>> Basically I will like to combine a social security number (9 digits)
>> and a birth date (8 digits, could be padded to be 9) and obtain a new
>> 'student number'. It would be better if the original numbers can't be
>> traced back, they will be kept in a database anyways. Hope this is a
>> bit more specific, thanks!!!
> last_number_used = 123  # or some other appropriate value
> def make_studentID():
>     global last_number_used
>     last_number_used = last_number_used + 1
>     return last_number_used
> For a real application, I'd check the database to see if the number has
> already been used before returning the number. Also, if you need more
> than four digits in your IDs, I'd add a checksum to the end so you can
> detect many typos and avoid much embarrassment.
> In a real application you would need to store the global variables in a
> database, otherwise each time you reload the Python script you start
> generating the same IDs over and over again.

For real applications (ignoring your theoretical need to generate the
numbers in a random order) I'd not only store the number in the
database - I'd let the databae generate it. Most have some form of
counter that does exactly what you want without needing to keep track
of it and check the database for consistency.

Mike Meyer <mwm at mired.org>			http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.

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