SAP PI 7.4 REST Adapter Authentication

Hello,

I have a scenario where in I need to call an API from a thirdparty site. they utilize HMAC-SHA1 security. They provided me a key and a secret. They needed a signature as well to authenticate..how can I create this signature? is that a standard functionality for the SAP REST adapter or should i need to write a JAVA code?

I need to generate a URL something similar to this to access this API, how should I configure the REST adapter? We have PI 7.4 SP12

https://api.serviceonline.com/v1/search/datafile?timestamp=1369844777731&key=fCTYXpuGkVcnDf6JLSSbtA==&signature=8qrFmQbQgILzdDeQfbJTxHXeZvE=

All security values shown here are for illustration purposes only.

Thank you.

Larry.