We are building security for our entire cloud API patterned off of Amazon’s HMAC -SHA signatures.
Our REST API is secured with these signatures, so why shouldn’t the Electric Imp?
Here is a full explanation if you want the gory details:
http://docs.aws.amazon.com/AmazonSimpleDB/latest/DeveloperGuide/HMACAuth.html
I have built and tested a working example if anyone wants the Squirrel code. Enjoy!
https://github.com/fgarsombke/electricimp/blob/master/hmacsha256amazon.nut