All API calls that make a change within the Dfns system need to be signed by a user. This ensures that only authorized users are able to make changes within the system, and the signature can be used to audit changes at a later time.
Signing is a three step process:
Get a challenge from the Dfns system.
Sign the challenge, and return to the Dfns system.
Get back a User Action Signature, and include it with your original API call.