With the exception of DID registration (did_register), each HTTP request to the IDIN server must contain a request nonce ("nonce"). A nonce is bound to a DID address and starts at one for the first HTTP request after the DID registration. The DID nonce then increases by one for every request, and as a result it counts to the total number of requests that the DID has made.
The current nonce of a DID (<did_address>) can be obtained with a GET request.
If the input nonce ("nonce") in a HTTP request does not match the current nonce of the given DID, the request will be rejected by the IDIN server.