ib technology
Access Condition for Sector Trailer Block
The read/write access to the Keys and the Access Bits themselves is controlled by the access
conditions for the Sector Trailer Block. The read/write access is specified as “Never”,
“KeyA”, KeyB” or Key A|B (KeyA OR KeyB).
Access Bits Access condition for:
KEY A
ACCESS BITS KEY B
C1 C2 C3 Read Write
Read Write
keyA never
keyA keyA
keyA never
keyA|B keyB
keyA|B never
keyA|B keyB
keyA|B never
keyA|B never
Read Write
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
never keyA
never keyA
never never
never keyB
never keyB
never never
never never
never never
keyA keyA (KeyB can be read)
keyA keyA (Transport setting)
keyA never (KeyB can be read)
never keyB
never keyB
never never
never never
never never
The new Mifare cards have the access conditions predefined as transport configuration:
C1 C2 C3 = (0 0 1) which means Sector Trailer Block can only be read or written to using
KeyA and KeyA itself can never be read.
Because the Access Bits themselves can be locked great care must be taken when any of these
settings are changed because they may be irreversible making the card unusable.
Access Condition for data areas
The read/write access to the data areas is also controlled by the access conditions defined in
the Sector Trailer Block. The read/write access is specified as “Never”, “KeyA”, KeyB” or
Key A|B (KeyA OR KeyB).
A data block can be a “read/write block” or a “value block”. For a “read/write” block the
basic read and write operations are allowed. For the “value block” the additional increment,
decrement, transfer and restore operations can apply. In one case (001) only read and
decrement are possible for a “non-rechargeable” card application and in another case (110)
recharging is only possible using keyB.
The default transport configuration specifies that the data areas can only be accessed using
KeyA|B, however the operation of the Mifare cards define that “IF KEYB CAN BE READ
IN THE CORRESPONDING SECTOR TRAILER THEN IT CANNOT SERVE FOR
AUTHENTICATION”. This means that for the transport configuration (and 001 and 010
cases), KeyA must be used for access.
Note also that the read-only status of the Manufacturer Block is not affected by the access bits
setting.
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