For more information on Mifare 1k Tags, the memory layout and more details you can visit these pages: More about Mifare in general can be found on Wikipedia. (taken from the Mifare Datasheet, link see below) Here is a basically memory layout of a Mifare Classic tag: This section is only writeable on some special chinese tags. Sector 0 Block 0 also contains a non changeable UID (the tags unique ID) and some manufacturer data. As an example you can define to use Key A for reading the block and Key B for writing to it. Each sector has two keys: Key A and Key BĮach of the 16 sectors can define it’s own access right and wich key is needed for a particular action. Each block contains 16 bytes of data.īefore reading a sector, the reader must authenticate to the tag with a secret access key. Each of these sectors has 3 blocks of data storage and 1 block for storing the secret access keys and access controls. More deatiled Information about this can be found in the following links:Ī Mifare Classic 1k tag contains 16 sectors. Mifare Classic in general is stated insecure, because it’s encryption protocol has been cracked. There are also other types like the “Mifare Classic 4k” and the “Mifare Mini” each having a different memory size. 1k stands for the size of data the tag can store. The NFC tag I analyzed is a so called “Mifare Classic 1k” tag. You can also recharge your tag via the machine if you run out of credits. You can touch it with your tag to buy some drinks and the corresponding price is subtracted from the ammount stored on the tag. In this example the vending machine has an active NFC reader built in.

This is usually used when sending data for example in “Android Beam”. There is also an active - active mode where both endpoints can send data and need to be powered seperately. It also powers the passive device via an electromagnetic field. The active device scans for the passive one and establishes a connection on contact. Basically there is an active NFC enabled device (the reader) and a passive device (the tag). NFC nowadays is used for access cards, public transport, some more and in this case: Vending Machines. For more Infos on NFC you can read the Wikipedia article. NFC stands for Near Field Communication and is used to communicate over short distances.

At the end I show you how to reprogram a vending machine’s NFC tag to contain more credits. In this blog post I will cover some quick basics about NFC, Mifare Classic and how to set up everything for reading and writing a NFC tag.

Mifare cracking