validating "per use" licensing

[Dr. Hawkins]

I want people to be able to pay "per use" for the product.  In this case,
it would mean per client file.

My thinking is that I embed a large random string in the source code of
their copy, and keep a copy of the string myself.  When a license is
purchased, it would be for a particular last name and last four digits of
that client's social security number.  Upon payment, my server would run a
hash on the random string, the name of my customer, and the client info
from their customer, and produce a key.  At the client end, this key is put
in a list.  When the program runs, it would run the hash, and if the key
exists, it could proceed.

Is this a sensible approach?  And and any suggestions on the hash to use?


-- 
The Hawkins Law Firm
Richard E. Hawkins, Esq.
(702) 508-8462
HawkinsLawFirm at gmail.com
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