El Bloc de Toni Cunyat

A very frustrating action when you write an RFID card is to get it bricked, e.g. by overwriting the trailer block with inconsistent values. A 1KB Mifare Classic card has 16 sectors of 4 blocks with 16 bytes per block (64 blocks at 16 bytes). The trailer block is the last block for each sector, so from the 1KB of capacity we must subtract 16 bytes due to the first block (where the identifier is) and the 16 tail blocks (blocks 3,7,11,15... 59, and 63). This block is where the keys A and B for access to the remaining blocks of the sector are stored, as as well as the access bits. It essentially indicates what is readable and writable and what is the password to do so. So the effective capacity is: (64 blocks - 16 trailer - 1 header)*16bytes = 752 usable bytes . 0 E9D517B49F0804006263646566676869 1 00000000000000000000000000000000 2 00000000000000000000000000000000 3 FFFFFFFFFFFFFF078069FFFFFFFFFFFF ← bloque trailer 4 00000000000000000000000000000000 5 00000000000000000000000000000000 6 0...

 I had seen people copying and writing Skylanders with NFC readers, like the proxmark or the ACR122U, but nowhere had I seen how to clone one of these figurines with an MFRC522. I already had Arduino microcontrollers so choosing an MFRC522 was the cheapest way to go. I didn't find any sketch or example of how to make a generic reading or copy, I mean for each RFID card I had to create a sketch where I included in the code the keys and the writing or reading functions adapted to the one I wanted to do in each occasion. These readers are very cheap, although it is true that you can get them for 1€ or less, you have to be very careful because not all readers/writers are of the same quality. I can confirm that only one of the 2 MFRC522 readers I have can read Skylanders, the other one supposedly fails due to a lack of power. You can make modifications to increase the power but it is always better to buy a tested unit. Anyway, even in the 1€ model we will be able to write our backups on...