Standard Transfer Specification Association
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Token Identifier (TID) Rollover

The Token Identifier is a 24 bit field, contained in STS compliant tokens, that identifies the date and time of the token generation. It is used to determine if a token has already been used in a payment meter. The TID represents the minutes elapsed since the 1st January 1993. The incrementing of the 24 bit field means that at some point in time, the TID value will roll over to a zero value.

All STS prepayment meters will be affected by TID roll over on the 24/11/2024. Any tokens generated after this date and utilizing the 24bit TID will be rejected by the meters as being old tokens as the TID value embedded in the token will have reset back to 0.

In order to overcome this problem all meters will require key change tokens with the roll over bit set. In addition to this, the base date of 01/01/1993 will be required to be changed to a later date. This process will force the meters to reset the TID stack to 0. To avoid previously played tokens from being accepted by the meter due to the TID stack reset, the key change process must introduce into the meter, a new decoder key.

A process is therefore required to allow for the management of this change with the least impact to the Utilities and equipment suppliers.

For more information on the TID rollover, please see the STS402-1 Code of Practice.

Please click here for the TID Rollover microsite.

Project timelines

The table shows the TID rollover project timeline.

Current project status

  1. Base dates have been defined and published in Edition 2 of the IEC62055-41 specification in 2014.
  2. Key Management Centre has been updated to include the base date for each Vk in the key load file.
  3. Secure module firmware has been updated in the latest secure module versions to support the rollover functionality.
  4. Key management centre will go live in Q1 2017.
  5. A new specification (application programming interface - API) will be published in Q1 2017.

Note for manufacturers:

  1. Vending systems must be updated to cater for the new base dates and API specification, starting in Q2 2017.
  2. All legacy security modules must be updated to the latest level security modules, with base date and TID rollover support.
  3. All Vending customers should be advised by vending system manufacturers to upgrade their vending systems to handle the TID rollover. Priority item!

Note for Utilities:

  1. Plans to be drawn up to handle the keychange rollover program
  2. Key changes should be piloted on smaller meter numbers initially to test the program
  3. Vending systems to be upgraded to handle the TID rollover functionality - this is a priority item!

Frequently asked questions:

Do I have to upgrade the firmware in my meters in the field?

No. The meters in the field already support the TID rollover functionality. A rollover keychange must however be done on each meter. Security and vending systems will require an upgrade to the STS6 protocol to be able to do this rollover keychange. Several methods exist for performing this rollover keychange:

  1. Let the vending system generate the keychange tokens automatically when the meter key changes. If the parameters of the meter (such as KRN, TI, SGC) change, the vending system will generate the keychange tokens automatically the next time a token is requested for that meter. The user will then enter the keychange tokens first, followed by the generated token. This is by far the simplest and least expensive option.
  2. The utility visits each meter and inserts the rollover keychange tokens on behalf of the user - this is costly in labour

    No. The meters in the field already support the TID rollover functionality. A rollover keychange must however be done on each meter. Security and vending systems will require an upgrade to the STS6 protocol to be able to do this rollover keychange. Several methods exist for performing this rollover keychange:

    1. Let the vending system generate the keychange tokens automatically when the meter key changes. If the parameters of the meter (such as KRN, TI, SGC) change, the vending system will generate the keychange tokens automatically the next time a token is requested for that meter. The user will then enter the keychange tokens first, followed by the generated token. This is by far the simplest and least expensive option.
    2. The utility visits each meter and inserts the rollover keychange tokens on behalf of the user - this is costly in labour

No. The meters in the field already support the TID rollover functionality. A rollover keychange must however be done on each meter. Security and vending systems will require an upgrade to the STS6 protocol to be able to do this rollover keychange. Several methods exist for performing this rollover keychange:

  1. Let the vending system generate the keychange tokens automatically when the meter key changes. If the parameters of the meter (such as KRN, TI, SGC) change, the vending system will generate the keychange tokens automatically the next time a token is requested for that meter. The user will then enter the keychange tokens first, followed by the generated token. This is by far the simplest and least expensive option.
  2. The utility visits each meter and inserts the rollover keychange tokens on behalf of the user - this is costly in labour

Do all meters support the rollover keychange?

The IEC62055-41 specification, as well as the original STS specification documents call for support of the rollover functionality since inception of the specifications. All meters should therefore support this. If you are unsure if your meter supports this rollover functionality, then simply take one of the older meters from the field and send it to the STSA to be tested free of charge. This will require that the meter is reset to factory conditions, with a known key for testing. This may be arranged with the original manufacturer of the meter.