Hello,
itchycube wrote:how does it work when writing to a different card than the dump was taken from? Obviously the UID will differ - but from what i've read here thats just a warning.
Yes, UID differ but you can't wrote the manufacturer block (block 0 at sector 0) so don't care about that.
itchycube wrote:How does it work in general though with the keys though?
General thought for key is key_a = reading, key_b = writing. key_a could be public, key_b stay private.
itchycube wrote:Can you change the keys on a card?
Yes, If you have suffisent permission to change keys (it depends on access bits, please read Mifare Classic Spec).
itchycube wrote:How do most Mifare systems handle keys??
AFAIK, most Mifare are actually used in transport/ticketing application. Yeah, that's scarying... the security of Mifare Classic is similar to WEP algorithm in WiFi (key can be recovered in few minutes) but in near future, Mifare Classic's main usage will be light data carrier i.e. VCards, URL, etc.
In theses applications, you should follow "Mifare Application Directory" specs recommandations (i.e. public key A) to be compiliant with others systems.
itchycube wrote:Any info or links to the right stuff would be greatly appreciated.
Have a look to Mifare Classic specifications (public access) and Mifare Application Directory (public access).
Hint: An implementation (libfreefare) of theses specs is available under LGPL at nfc-tools' project.
http://code.google.com/p/nfc-tools/
http://code.google.com/p/nfc-tools/sour … ibfreefare
Hope it helps.
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Romuald Conty
Romuald Conty