On Sep 29, 2009, at 4:56 AM, William Hudson wrote:
There are many sources for credit card prefixes (as well as check
digit
algorithms) for validating credit cards. For example,
http://en.wikipedia.org/wiki/Bank_card_number
Part of the problem, as pointed out by the chart, is different cards
have different number lengths. They range from 13 digits to 16 digits.
For example, someone who accidentally leaves the first digit off of
their mastercard or visa could look like a valid amex card.
Again, it depends when you're doing your authorization check. If
you're processing immediately during the users' session, you don't
need to ask for the card type because an entry error will be caught
(assuming you've got a decent merchant processor).
However, lots of purchase systems do a deferred authorization check,
to allow the seller to have a look at the transaction before its put
through the system (often for additional fraud protection or inventory
clearance). In this instance, it's better to ask for the card type to
give you a piece of redundant information for the validity check.
In shopping cart and checkout systems, things are rarely as easy as
they seem.
Jared
Jared M. Spool
User Interface Engineering
510 Turnpike St., Suite 102, North Andover, MA 01845
e: [email protected] p: +1 978 327 5561
http://uie.com Blog: http://uie.com/brainsparks Twitter: @jmspool
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