Why entering invalid SO-PIN in HSM 2 bricks the device?

Nitrokey Support English
#1

I wonder why entering SO-PIN more than 15 times (default value) bricks the device? Is it forced by hardware (i.e. internal smart card works this way) or was that implemented separately? I believe that initializing such device again would wipe data from it, so there should be no problems with it?

1 Like
#2

Hi!

This is a hardware security latch, which makes smart card unusable. We do not have any method for reinitializing a device with used up attempt counter for SO PIN.

#3

So this is as I suspected. Thank you for an answer.

#4

Can default amount of max tries (times of attempts to enter a pin) be increased in settings?

How many can be set as a maximum retries before it bricks?

#5

It is not possible to change the default attempt count for the SO PIN as far as I see in the manual. For the User PIN I have found Retry Counter Initial Value field in the INITIALIZE DEVICE APDU. Looking at sc-hsm-tool help screen I see its value can be defined during initialization (no range declared):

$ sc-hsm-tool --help
sc-hsm-tool: unrecognized option '--help'
Usage: sc-hsm-tool [OPTIONS]
Options:
  -X, --initialize              Initialize token
  -C, --create-dkek-share <arg>
                                Create DKEK key share and save to <filename>
  -I, --import-dkek-share <arg>
                                Import DKEK key share <filename>
  -W, --wrap-key <arg>          Wrap key and save to <filename>
  -U, --unwrap-key <arg>        Unwrap key read from <filename>
  -s, --dkek-shares <arg>       Number of DKEK shares [No DKEK]
      --so-pin <arg>            Define security officer PIN (SO-PIN)
      --pin <arg>               Define user PIN
      --pin-retry <arg>         Define user PIN retry counter
(...)

$ man sc-hsm-tool
(...)
       --pin-retry value
           Define number of PIN retries for user PIN during initialization. Default is 3.
#6

Is it really ‘bricked’ (aka not more usable) or is only a new initialization/PIN-change permanently impossible ?

If I got it right, I need the SO-PIN only for initialization- and PIN-change processes, therefore a ‘try’ will be only accounted there.

#7

Both, initialization code (aka SO-PIN) and User-PIN have a retry counter that will eventually expire after wrong PIN presentation.

The SO-PIN has a retry counter of 15, the User-PIN can have up to 10 retries, depending on the selected PIN length (6=3, 7=5, >7=10). For the User-PIN the retry counter can be defined during initialization.

A blocked User-PIN can also be unblocked and reset, if that has been allowed during initialization.

For a block SO-PIN there is no recovery possible. You could only try a firmware update to reinstall from scratch.