If you are using STS prepayment energy meters, you might remember that updates are required for the key management centre (KMC), the security modules and the vending software.
Cryptographic Key Change
After the updates a key change is necessary for each installed STS energy meter operating on base date 1993. Those meters already operating on base date 2014 do not need to have their meter keys changed.
If you haven't updated the vending software by now, you can be sure that all of your meters need a key change.
The STS association suggests two different options:
1. The end-customer may be issued with the key change token pair at the time when he next purchases credit at a vending station. He then enters the token pair into his meter himself before he enters his newly purchased credit token.
2. A dedicated field-service team may be used to visit each meter and then enter the key change token pair.
From my point of view only the option #1 is possible on large scale.
Why is this necessary?
A unique token identifier (TID) is coded into the token every time when a token is generated at the vending station. This TID is calculated as the number of minutes elapsed since the base date 1993. The meter stores the TID to prevent a token replay.
The TID is a binary coded 24 bit field. This means, at a certain date the TID field will be full and rolls over to all bits equal to zero. This magic date is the 24. November 2024 at 08:15 pm.
Then the TID shows:
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
One minute later it changes to:
All tokens generated after that date will not be accepted by the meter, because the internal comparison shows that the token generation is too old.
The STS association has published a guideline to handle the rollover properly. Find more information and a calculator for the required time for key-changes here.
After the TID rollover key change, the new TID will be calculated from the 2014 base date and will have a lifespan up to year 2045.
Click the button to see the actual TID status for your time zone.
I hope that all utilities using STS meters understand the importance. Otherwise, it will be pretty much dark in some countries after November 24, 2024.
The clock is ticking.
As we don't have any conference this year it's very difficult to get the actual planning- and implementation status of the utilities worldwide.
CLOU vending systems can be updated and some customer already ordering meters with the new base date 2014.
If you are involved, please share your thoughts with us.
Thank you for reading.
Editor's note: This article was originally published in August 2020 and has been updated for comprehensiveness.