Enabling Production Mode - SCM

If left in Development Mode, self-destruct events are simulated with LED flash sequences and recovery rather than destruction to allow for experimentation with the security functions. The LED sequence will repeat three times and then the system will recover.

The table below summarizes the differences between Development Mode (no Bind Lock) and Production Mode (Bind Locked)

Once locked, setting the Event Action modes are limited in the following way:

When you have completed your development work with the SCM and are ready to deploy your system into the field, we recommend that you permanently bind your SCM to a specific host device.

Summary of Steps

Develop your application

[ ] Ensure your host has all the necessary prerequisites in place to interface with the SCM and that it will be able to run your software application.

Activate Production Mode

[ ] Permanently bind your SCM to the host device.

Develop your application

The following steps should be complete:

[ ] Install a battery on the Zymbit SCM I/O board.

[ ] Install all necessary software for your application on the host and establish temporary binding in development mode.

After these steps have been completed, you are ready to prepare your device for permanent binding.

Prepare Perimeter Detect

The Perimeter Event Actions for your SCM should be set to none or notify only. If your SCM’s action mode is set to self_destruct, you might render your unit /c/Users/bobgu/OneDrive/Desktop/Atom.lnkuseless while attempting to activate Production Mode.

To do this quickly, with the SCM client libraries installed, you can run the following shell command to use the Python API to communicate with the SCM and set the Perimeter Event Actions to only Notify when triggered:

python3 -c "import zymkey;
for ch in (0, 1):
    zymkey.client.set_perimeter_event_actions(ch, action_notify=True, action_self_destruct=False)
zymkey.client.clear_perimeter_detect_info()"

Prepare your application

You should then install your application on your host SBC. The SCM root partition is pre-encrypted and is secured by the SCM itself.

Test, debug, and test again

Test the functionality of your application thoroughly to ensure it is free of major defects that will prevent it from functioning properly. In Production Mode when Perimeter Detect features are in use, it may be difficult to make significant changes to your configuration without locking youself out of the SCM, depending on the nature of your application and its configuration.

Activate Production Mode

To put the SCM into Production Mode only requires a function call followed by a power cycle.

The API function lock_binding puts the SCM into Production Mode. Below are three examples which check the current binding info, lock the SCM binding, then check the current binding info again. Remove the comments around the lock binding function to move to Production Mode.

// gcc example_binding.c -I /usr/include/zymkey -l zk_app_utils -o example_binding

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "zk_app_utils.h"
#include "zk_b64.h"

void check_code(int code, char* location){
  if (code < 0)
  {
    fprintf(stderr, "FAILURE: %s - %s\n", location, strerror(code));
  }
  else if (code >= 0)
  {
    fprintf(stdout, "SUCCESS: %s - %d\n", location, code);
  }
}

void HSM_soft_bind(zkCTX zk_ctx)
{
  bool binding_is_locked = false;
  bool is_bound = false;
  int ret = zkGetCurrentBindingInfo(zk_ctx, &binding_is_locked, &is_bound);
  check_code(ret, "zkGetCurrentBindingInfo");
  printf("Binding is locked: ");
  printf(binding_is_locked ? "true" : "false");
  printf("\n");
  printf("SCM is bound: ");
  printf(is_bound ? "true" : "false");
  printf("\n\n");

  //ret = zkLockBinding(zk_ctx);
  //if(binding_is_locked && is_bound)
  //{
  //  check_code(ret, "zkLockBinding - Already Bound");
  //}
  //else
  //{
  //  check_code(ret, "zkLockBinding");
  //}
  //printf("\n");

  ret = zkGetCurrentBindingInfo(zk_ctx, &binding_is_locked, &is_bound);
  check_code(ret, "zkGetCurrentBindingInfo");
  printf("Binding is locked: ");
  printf(binding_is_locked ? "true" : "false");
  printf("\n");
  printf("SCM is bound: ");
  printf(is_bound ? "true" : "false");
  printf("\n\n");
}

int main()
{
  zkCTX zk_ctx;
  int status = zkOpen(&zk_ctx);
  check_code(status, "zkOpen");
  printf("\n\n");

  HSM_soft_bind(zk_ctx);

  status = zkClose(zk_ctx);
  check_code(status, "zkClose");
  printf("\n");

  return 0;
}

#include <stdio.h>
#include <zkAppUtilsClass.h>

using namespace std;
using namespace zkAppUtils;

void HSM_soft_bind(zkClass* zk_inst)
{
  bool binding_is_locked = false;
  bool is_bound = false;
  zk_inst->getCurrentBindingInfo(binding_is_locked, is_bound);
  printf("Binding is locked: ");
  printf(binding_is_locked ? "true" : "false");
  printf("\n");
  printf("SCM is bound: ");
  printf(is_bound ? "true" : "false");
  printf("\n");

  //zk_inst->lockBinding();
  //printf("lockBinding successful\n");

  zk_inst->getCurrentBindingInfo(binding_is_locked, is_bound);
  printf("Binding is locked: ");
  printf(binding_is_locked ? "true" : "false");
  printf("\n");
  printf("SCM is bound: ");
  printf(is_bound ? "true" : "false");
  printf("\n");
}

int main()
{
  zkClass* zk_inst;
  zk_inst = new zkClass();

  HSM_soft_bind(zk_inst);

  delete zk_inst;
  return 0;
}

import zymkey
tup = zymkey.client.get_current_binding_info()
print("SCM is bound: " + str(tup[1]))
print("Binding is locked: " + str(tup[0]))

#zymkey.client.lock_binding()

tup = zymkey.client.get_current_binding_info()
print("SCM is bound: " + str(tup[1]))
print("Binding is locked: " + str(tup[0]))

Finalize your device for deployment

After using the APIs to lock binding, reboot. The blink pattern on the SCM will change to 3 rapid blinks once every 3 seconds to indicate that SCM has bound to the host in Production Mode.

If you are using the Perimeter Detect features, close your perimeter circuits (for example, by closing the enclosure’s lid), and then clear any Perimeter Detect Events using the API:

python3 -c "import zymkey; idx = 0;
zymkey.client.clear_perimeter_detect_info()
for p in zymkey.client.get_perimeter_detect_info():
  if p:
    print(f'Channel {idx} has a detected breach event. Clear the Perimeter Detect Events again.')
    idx += 1
  else:
    print('No perimeter breach detected.')"

If you get a message that a breach event was detected from the above command, run it again to ensure all events have been cleared.

When it confirms that no breach events have been detected, it is then safe to arm the system by setting the Perimeter Event Actions to notify or selfdestruct, if desired.

Your system is now armed and ready to be used in the field!