The Sign In App API uses the Basic Authentication header. The header consists of the key and secret that were generated when creating the API client.
Basic authentication: The user ID is your key, and the password is the secret.
Example
Authorization: Basic PGtleT46PHNlY3JldD4
> curl -u <key>:<secret> \
-H "Content-type: application/json" \
-H "Accept: application/json" \
-X GET \
> curl -u <key>:<secret> \
-H "Content-type: application/json" \
-H "Accept: application/json" \
-X POST \
-d '{"key1": "value1", "key2": "value2"}' \