Extensions concept - khpos/Payment-gateway_EN GitHub Wiki
The payment gateway supports "extensions" in version 1.0. Extensions will help you retrieve additional parameters that might be interesting for your use-cases, but would rather bother other merchants. Extensions are independent and you can use multiple extensions at the same moment in time. Extensions are activated.
Technically speaking, extensions are more flexible than changes to the core API structure because extensions do not impact the cryptographic signing of core API operations. Each extension has its own signature, i.e. the gateway validates merchants' requests and so should the merchant validate the responses.
Extensions are not specific API operations. Extensions are integrated into the existing API operation in a transparent way, with their own signatures (as briefly characterised above). Please refer to the specs of individual extensions for more technical information, as well as actual examples.
Currently available extensions
Exact date and time of transaction authorization