Topic: Question for Mifare Classic Nested Authentication

Hi,

i am currently developing an application that implements Crypto-1 based on the published documents (Dismantling MIFARE Classic, Wirelessly Pickpocketing a Mifare Classic Card and DA by Henryk Plötz).

I successfully implemented a mutual authentication procedure, that allows me to authenticate a Mifare classic card with one block at a time (knowing the block key).

Now, i would like to implement nested authentication. So far, i managed to receive a ciphered nonce, after sending a ciphered authentication request to another mifare block.

My question is, how do i proceed now? As far as i understand it from the publications, i have to initialize my LFSR with the new key (which i know). Afterwards the protocol continues as within the "simple" authentication.

Do I have to decipher the nonce before i shift it in my LFSR (nt ^ uid >> LSFR, or {nt} ^ uid >> LSFR)?

Thanks,

cr