Access Conditions in MIFARE Classic 1K

1. Card Structure Memory: MIFARE Classic 1K has 16 sectors, each with 4 blocks (16 bytes each). Trailer Block: The last block (Block 3) contains Key A, Key B, and access conditions.

2. Keys Key A: Used for reading and writing. Key B: Typically used for writing.

3. Access Conditions Access conditions are defined by three bits: C1, C2, and C3, stored in the trailer block. These bits control read/write permissions for each block.

4. Access Condition Table C1 C2 C3 Read Access Write Access 0 0 0 Key A or B Key A or B 0 1 0 Key A or B Never 1 0 0 Key A or B Key B 1 1 0 Key B Key B 0 0 1 Key A or B Never 0 1 1 Key A or B Key B

5. Setting Access Conditions To configure access:

Blocks 0-2: Allow both keys to read, only Key B to write. Sector Trailer: Allow Key B to modify keys/access conditions. 6. Encoding Access Conditions Access bits are encoded as follows:

Byte 6: ~C1, ~C2, ~C3 Byte 7: C1, ~C2, ~C3 Byte 8: C1, C2, C3 Conclusion Access conditions in MIFARE Classic 1K cards determine how data is accessed and modified. Understanding and configuring C1, C2, and C3 bits effectively is essential for card security.