Standard Transfer Specification Association
Standard Transfer Specification Association



The STS Association, as the custodian of the STS prepayment metering technology standard was founded in 1997. The key operational objectives of the association are to maintain the necessary infrastructure; promote the technology internationally and further develop the standard to meet emerging international demands for additional functionality. The Association ensures interoperability between system components from different manufactures of prepayment meter and vending systems by accrediting and maintaining a list of test laboratories that ensure compliance to STS standards. The Association manages the availability of encrypted vending keys to manufacturing members via its key management centres, and ensures consistent use of manufacturer codes as well as meter serial numbers. 

In keeping with the fast progressive technology, STS Association has established Working Groups for on-going standard enhancement projects.

Working Groups, comprising technical experts from STS Association member organizations and the industry are currently involved in a number of projects related to the ongoing maintenance of the standard, as well as new developments such as:

  • Enhancements to the encryption key management system to allow for distributed key management using multiple key management centres worldwide;
  • The definition of a currency token specification to handle a wide variety of currencies. 
  • The introduction of more secure encryption and decryption algorithms, as well as decoder key generation algorithms. 
  • The definition and publication of a code of practice for the Token ID rollover, along with the introduction of 3 distinct base dates.
  • The publication of Editions 2 and 3 of the IEC 62055-41 standard containing revisions and added functionality.
  • Harmonisation of the STS into the DLMS/COSEM protocols to allow the STS to be used in the Smart Meter markets.
  • Preparation work for the introduction of future enhancements of the IEC standards.

Further information about the Standard Transfer Specification and the STS Association may be found on the Association's website or by contacting the Secretariat.

Secretariat: Mr. Jean Venter, c/o Van der Walt & Co.

P.O. Box 868, Ferndale, 2160, Johannesburg, South Africa.

Tel: +2711 061 5000


The standard transfer specification (STS) is a secure message protocol that allows information to be carried between point of sale (POS) equipment and payment meters. It caters for several message types such as credit, configuration control, display and test instructions. It further specifies devices and codes of practice that allow for the secure management (generation, storage, retrieval and transportation) of cryptographic keys used within the system.

The STS is deployed using various devices and other entities within the system. Examples of these are the key management centre, secure module, prepayment meter, token, key load file, meter card, communications port, standard token translator, credit dispensing unit, system master station, cryptographic keys, supply group and operators like the utility, consumer, vendor, meter manufacturer and secure module manufacturer.

These entities are tagged with identifiers like country code, ISO BIN, supply group code, meter number, manufacturer code, tariff index, token identifier, key revision number and key type.

Various functions are embodied in these entities such as token transfer functions, which carry instruction messages to the prepayment meter from the vending point or the management system and security functions like encryption/decryption algorithms used to secure the messages that are transported between entities within the system.

The diagram below shows the relationships between entities in an STS based system