Does anyone knows how to interact with Notary server with curl?

Although Notary client provide all the feature needed, the authenticate process is time consumed. In automation scenario, hundreds of images needed to be downloaded with content trust, if each time with a boring authentication, it wast too much time.
So curl with token way seems to be a better option.
However, as there is no Notary Server API documentation, so how to interact with Notary server by curl? For example, authenticate, lookup a digest for an image.
Can anyone can help?
Thanks in advance