RFID Card Numbers Question

[Bazzinga]

Hello again,

While browsing different sections of the forum I read a little more on the subject, but something still bugs me. For example, if an RFID card has this number written on it 0006247169 095, 21249, then how do I tell that the stream of bits read from the RFID reader is actually this number? In other words, hacing in hand the bits that I got from the RFID reader, how can I find the card number? Is there like an algorithm or something?

Thanks in advance

 

[FvM]

More specifically, there are different RFID standards that each define an uinique method to query cards and decode IDs from card bits. Reasonably, you'll search for a specific card protocoll on the internet or ask in the forum.

 

[betwixt]

I've seen cards with the decimal version of the embedded number printed on them although internally it is always in binary. I've also got a stack of cards here printed with numbers that bear no relation to the one inside them. Bear in mind that these are often used for secure locking and logging systems where the printed number is only used for administrative purposes and the internal number is only known to the security department. Obviously printing the internal number on the outside makes it easier to clone the card.

Brian.

 

[Bazzinga]

Yes, it makes sense. But the thing is that I've seen that only by having just the last 8 digits of my above number you can actually store the card in a server (for example). In my previous job, I've worked a little with elevator and we restricted the access of resident to the elevator by means of RFID technology, and the thing was that when we registered the cards on the servers, we only took the last 8 digits. Sadly enough, I never bothered to ask how they managed that situation. That why I'm kind of confused to how the decoding is done.

- - - Updated - - -

But now that I look at it, the first three of the last eight digits are the facility code. Since there are 8 bits for the facility code (Wiegand26 format), this can go up to 255. While the remaining 5 comprise the other 16bits, so it can go up to 65535. That makes 24 bits, plus the even parity bit plus the odd parity bit makes a total of 26bits, hence the Wiegand26. So it must probably be this. But then what do the first 10 digits refer to?