A supply group code is a 6 digit number used to geographically demarcate regions of payment meter installations. The SGC is allocated by the Key Management Centre to a Supply Group Owner. The vending key of the supply group is created using this SGC number as an input parameter, thus making the vending key unique for each supply group.
The SGC should be allocated to a geographical region of payment meter installations to isolate the installation base to a unique vending key. The benefits of this are that the payment meters in one SGC are isolated from payment meters in other SGC regions, thus allowing payment meter management by regions. Should a vending key be compromised, this would affect only that region of payment meters. In addition to this, it allows for the SGC owner to allocate multiple vendors of prepayment tokens to particular regions only.
Classification of SGC's
Default SGC - a SGC code which creates a vending key that can only be used to generate keychange tokens to another SGC, as well as other management tokens. No credit tokens may be generated using a default SGC. These SGC's are used typically to code payment meters from a factory to a customer, where the customer wishes to place the meters in storage and allocate a vending SGC at a later date. The meters are not usable as active payment meters until they have been key changed to a vending SGC. All manufacturers have default SGC's - payment meters may be shipped from the manufacturer to the customer coded to the manufacturer's default SGC, or the custmer's default SGC. In many cases, the meter is coded to the customers vending SGC if so required by the customer.
It is also possible to keychange a payment meter from one vending SGC to another vending SGC (for example, where the destination SGC owner does not have a vending key of the source SGC, and the source SGC owner does not have the vending key of the destination SGC) by first keychanging the payment meter from the source SGC to a default SGC, and then from the default SGC to the destination SGC. In this case, both parties involved in the SGC transfer must have the vending key of the default SGC. This is not a security risk since no credit tokens can be generated using the default SGC.
Vending SGC (unique)- an SGC that has a vending key asscoiated with it that allows the generation of credit tokens and management tokens for a payment meter coded to this SGC. Each token generated using this SGC will only function in the meter for which it is generated.
Vending SGC (common) - an SGC that has a vending key asscoiated with it that allows the generation of credit tokens and management tokens for a payment meter coded to this SGC. Each token generated using this SGC will function in any meter that belongs to this SGC. This type of vending key cannot be used for keypad meters. It is only used in meters that can have the token carrier erased after use since the token could otherwise be used again on another meter within this SGC (such as meters using magnetic cards as the token carrier).
Allocation of SGC's
SGC codes are allocated to an SGC owner by the Key Managment Centre according to the rules set out in the Code of Practice for the allocation of Supply Group Codes (STS401-1).