TPA Stream's REST API supports Basic Authentication over HTTPS using your Secret API Key.
To implement, simply put your user name (email address) and Secret API key in the Authorization header on each API request.
Your API key is a Secret Password! Do not share this key with anyone, including TPA Stream. TPA Stream will NEVER ask for your Secret API Key.
A simple example using curl:
curl -L --user firstname.lastname@example.org:MY_API_KEY https://app.tpastream.com/api/claims