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online payments and credit cards: I have questions
As I make the rounds doing year-end donations, I'm reminded of two things that have long puzzled me:
Some web sites auto-detect the type of credit card based on the number. Apparently all credit-card numbers that begin with "4" are Visa. (I don't know if the reverse is true: do all Visa numbers start with 4?) Being me, I've cycled through the other nine digits and nothing else produces a match based on a single digit. What are the patterns for other providers? And are all these sites using some standard library for this, or are programmers really coding that by hand?
Years ago, a three-digit code ("CCV") was added to cards to mitigate fraud. On a physical credit card, this number is stamped rather than embossed, so those old-style manual credit-card gadgets that took an imprint of your card (on actual paper, with a carbon!) couldn't record it. Um, that's fine I guess, but online, that number isn't any more secure than the card number itself. And someone who steals your physical card has the number; it's not a password. Does that number have another purpose?
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Yeah, if the credit-card provider weren't liable for fraud, my online payment habits would be different. I'm not quite sure what they'd be, but not this.
Way way back when the web was young and security was (even more) sketchy, I got a separate credit card to use exclusively for online transactions and gave it a modest credit limit. I figured concentrating all the risk in one place, and not co-located with a card where I'd ever signed for a purchase in a store, might help. No idea if that made any difference; mostly I rely on it being their responsibility to protect me. And I eventually raised that credit limit so I could buy the occasional large item, though I kept it below the ridiculous limits Visa was happy to offer.