Forum › MIFARE general topics and applications › What is MIFARE Classic 1K Access Bits means? How to calculate and use it? › Reply To: What is MIFARE Classic 1K Access Bits means? How to calculate and use it?
Hi Onyekachi,
The both diagrams in the post shows the access condition bits for the data blocks and for the sector trailer. You go into the diagrams and select the best aligned condition for your application. Not all conditions are possible! For instance, if you need separate keys (a read key and a write key), only the lines with “read = key A or key B” and “write = key B” are possible. There exist no condition “read = key B only” and “write = key A only”!
For instance, if you decide C1 = 1, C2 = 1 and C3 = 0, all data blocks can be read with key A or B and can be written only with key B. This is a typical use-case where the terminal (which has key A) can read data and decrement account values. But to write or renew account values is only possible on a special terminal (which has key B).
With the definitions of C1, C2 and C3 you have to fill the appropriate bits in bytes 6, 7 and 8. Please have a look into the datasheet. There is a table “Access Conditions” where is shown how the bits of C1, C2 and C3 (inverted and not) are put into the bytes 6, 7, and 8. You have to use this table and you cannot arrange the bits in a different order!
The TapLinx Team
The both diagrams in the post shows the access condition bits for the data blocks and for the sector trailer. You go into the diagrams and select the best aligned condition for your application. Not all conditions are possible! For instance, if you need separate keys (a read key and a write key), only the lines with “read = key A or key B” and “write = key B” are possible. There exist no condition “read = key B only” and “write = key A only”!
For instance, if you decide C1 = 1, C2 = 1 and C3 = 0, all data blocks can be read with key A or B and can be written only with key B. This is a typical use-case where the terminal (which has key A) can read data and decrement account values. But to write or renew account values is only possible on a special terminal (which has key B).
With the definitions of C1, C2 and C3 you have to fill the appropriate bits in bytes 6, 7 and 8. Please have a look into the datasheet. There is a table “Access Conditions” where is shown how the bits of C1, C2 and C3 (inverted and not) are put into the bytes 6, 7, and 8. You have to use this table and you cannot arrange the bits in a different order!
The TapLinx Team
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