Re: Prepaid Cards

I'm guessing he/she means "coming up with numbers which can't be hacked"?

That is, if I buy a phone card with the number 123-456-789-1, I shouldn't be able to guess that 123-456-789-2 is also valid and get some free credits.

If so, that's an interesting question, though not a Perl question as such.

($_='kkvvttuu bbooppuuiiffss qqffssmm iibbddllffss')
=~y~b-v~a-z~s; print

Comment on Re: Prepaid Cards

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Re^2: Prepaid Cards by CountZero (Bishop) on Mar 27, 2007 at 13:36 UTC
I doubt there is such a thing as "numbers which cannot be hacked", unless you go the cryptographic route. You start with a UUID and a checksumm over it and then code both with a secure cryptographic method of which only you know the key. It would be next to impossible to change a few numbers and end up with a valid UUID and checksum. If you combine that with a maximum number of tries before your log-in is locked-out and you have a pretty secure way of providing such "cards". CountZero "If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law	[reply]

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Re^2: Prepaid Cards
by CountZero (Bishop) on Mar 27, 2007 at 13:36 UTC

You start with a UUID and a checksumm over it and then code both with a secure cryptographic method of which only you know the key.

It would be next to impossible to change a few numbers and end up with a valid UUID and checksum.

If you combine that with a maximum number of tries before your log-in is locked-out and you have a pretty secure way of providing such "cards".

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law

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