Proxmark3 community

bigboyq

Contributor

From: China

Registered: 2015-09-22

Posts: 38

Can anyone tell me why Key B read failed

proxmark3> hf mf rdsc 1 A FFFFFFFFFFFF
--sector no:1 key type:A key:ff ff ff ff ff ff

#db# READ SECTOR FINISHED
isOk:01
data   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
data   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
data   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
trailer: 00 00 00 00 00 00 ff 07 80 69 ff ff ff ff ff ff
proxmark3> hf mf rdsc 1 B FFFFFFFFFFFF
--sector no:1 key type:B key:ff ff ff ff ff ff

#db# Cmd Error: 04
#db# Read sector  1 block  0 error
#db# READ SECTOR FINISHED
isOk:00
proxmark3> hf 14a read
 UID : 10 e2 b8 29
ATQA : 00 04
 SAK : 08 [2]
TYPE : NXP MIFARE CLASSIC 1k | Plus 2k SL1
proprietary non iso14443-4 card found, RATS not supported
Answers to chinese magic backdoor commands: NO
proxmark3>
proxmark3> hf mf chk 4 B FFFFFFFFFFFF
chk key[ 0] ffffffffffff
--sector: 0, block:  4, key type:B, key count: 1
Found valid key:[ffffffffffff]

It is obviously, Key A reading is correct, and KeyB is FFFFFFFFFFFF
Chk the block by Key B, it works properly
But while reading block with KeyB, failed.
and the control bit is  ff 07 80 69, I think it is correct
Anyone who can help me with this problem?

ikarus

Contributor

Registered: 2012-09-20

Posts: 249

Website

Re: Can anyone tell me why Key B read failed

Hi bigboyq,
the access conditions "ff 07 80" (transport configuration) state that key B is readable.
If key B is readable it is no longer considered a key but user data. Authenticating
with key B will still work, but reading blocks will fail. This is the intended behavior.

Quote from the Mifare Classic Data Sheet (page 14):

if Key B may be read in the corresponding Sector Trailer it cannot serve for authentication (all grey marked
lines in previous table). As a consequences, if the reader authenticates any block of a sector which uses
the grey marked access conditions and using key B, the card will refuse any subsequent memory access
after authentication.

Cheers
  ikarus

bigboyq

Contributor

From: China

Registered: 2015-09-22

Posts: 38

Re: Can anyone tell me why Key B read failed

Thanks for the explanations.
Hmm, it would be funny that people won't use keyB, probably might leave it default.
In this situation, keyB could be used for authentication. Nested crack and Harden nest might work.