Rfid system derived keys decryption

Hi,

I am on research of rfid security systems, I have selected one big network and have got from few tags all secret keys. I know this network use derived key encryption so I am interested is there any chance to get masterkey? Since I am totally noob in cryptographic any help would be very helpful:)

Here is the derived keys system 'master key: derived key = ENCRYPT(master key, card id)'

So I have few DERIVED KEYS and CARD IDS

CARD ID : DERIVED KEY a76161f1 : af4b2bc8fecc f7b380f1 : 094f18753908

So once again any help ideas or etc would be very helpful! Thanks

domc wrote: is there any chance to get masterkey?

Unlikely, unless it's a poorly designed system.

And how to research how system poorly or not designed? From where to start? I can't find from where to start…

And how to research how system poorly or not designed? From where to start? I can't find from where to start…

Before I start, I'll just say that I doubt that it's possible to get the master key.

domc wrote: derived key = ENCRYPT(master key, card id) Do you know how this ENCRYPT function works? If you do, then take a look at the algorithm and see if you can somehow reverse it using the derived key and card id to get the master key. If this works, that is what I meant by a poorly designed system.

If you don't have the encryption algorithm, finding it out should probably be your first step.

Firstly I would like to thank You starofale for replies with help.

One thing I know there is nothing impossible…

I don't know how encrypt works, so I don't have algorithm only thing I know how system works:

CARD UID (uniq id) > READER = (UID (ALGORITHM) = SECRET KEY (DERIVED KEY) >> LOGIN to CARD)

ALGORITHM UNKNOWN CARD UID KNOWN SECRET KEY KNOWN

things I can do:

1. I can do SNIFFING attack then reader and card is talking (MAN IN THE MIDDLE)
2. I can emulate card with specified UID and collect all data which reader send to card and card to reader

I have collected more than 60 secret keys (DERIVED KEYS) with dark side and nested attacks from cards

So how I can search for algorithm? I think there is should be math like X and Y if I am not wrong… Because there is only one unknown from three. And I can collect much data I can use FPGA for calculate. Sorry for that I am wrong or stupid questions I am very noob in cryptographic…