November 25th, 2003

belize

CVV2 Questions

The Internet is useless. I want to know why CVV2 codes on credit cards are supposed to be more secure and help consumers. Every website just tells me, "It protects you". But why?

Theories:

1) it's not embossed, so employee crooks at stores swiping cards with carbon paper don't get the CVV2 number.

2) it's not part of the hashing function within the card's primary 16 numbers, so even if you use a credit card generator program (trivial to write), you can't get correct CVV2 numbers, since only the card issuer has it.

3) merchants aren't supposed to store CVV2 numbers? So if their databases are hacked, nobody gets those? No... because I know Amazon and many others do.

I don't really think (1) and (2) happen much anymore compared to databases being hacked (3), and since everybody just puts CVV2 numbers in their databases, how does CVV2 really help?

Enlighten me!
belize

RAID

LiveJournal uses or has used:

Linux software RAID
AMI/Dell/LSI/whatever MegaRAID
Mylex DAC960 RAID
IBM ServRAID
Adaptec RAID
Intel gdth RAID

They all suck in different ways:

Adaptec corrupted data left and right. We replaced them all. MegaRAID has shitty, closed, unuseable tools and shitty /proc interfaces. Intel gdth is good with nice /proc interfaces, but some tools aren't so quick returning. None of them have anything near a consistent interface. IBM ServRAID seems great, but I think the control binary is closed? Maybe it's not anymore, with IBM being all pro-Linux. That was years ago. Still my favorite RAID array.

I really can't recommend any one of them. No, DAC960 is definitely the best.... no question. But they were bought and that line discontinued. :-(

*yawn*
belize

breadboard UARTs. Help?

I want to build a grid of christmas lights for the roof of my house where I can control each light (pixel) independently, and do a big video wall type thing.

My dad proposed a grid with shift elements along two edges.

Somehow I need to interface to a serial/parallel port and send along a few commands:

Shift 1 left
Shift 0 left
Shift 1 up
Shift 0 up
Light on
Light off

And hell, as long as I'm being lazy and fitting the commands into a byte, got plenty of room for other commands... maybe dimming commands to vary the voltage and fade things in and out?

If my display is 14 feet by 10 feet tall, and I do one pixel per 3" square, that's a resolution of 56 x 40.... I just brought that up in gimp and it's plenty of space to work with to do cheesy christmas animations.

Okay, so to refresh the display it'd take 1 + 56 + 40 + 1 = 98 commands... off, program horizontal, program vertical, on. 98 bytes (lazy encoding) = 882 bits, or 992 bits with a serial port adding a stop bit in 8-N-1 mode. With a 57.6kbps serial line I could do 60 fps, but that's overkill.... I'd hit problems with the lights fading out too slowly.

So, the real question: how do I interface hardware with a serial line? Can I buy a UART chip with a simple interface? What I think I need is some chip that gives me 9 pins: 8 data bits, and a "new byte ready" pin.

Help? (I'm such a LiveJournal question whore.)

Updates:
I found these MAX RS232 parts. Maybe what I need?