Retrieve JSON with HMAC/SHA256 Auth and custom fields

[SCH00N3R]

An API I want to connect to requires the following fields:

X-Time: (current UTC timestamp in ms, if timestamp is more than five minutes apart from server's time, the request will be rejected, example: 1543597115712)
X-Nonce: (random 36 char string, each nonce can be used only once, example: 4ebd366d-76f4-4400-a3b6-e51515d054d6)
X-Organization-Id: (organization id, example: da41b3bc-3d0b-4226-b7ea-aee73f94a518)
X-Request-Id: (required, unique identifier of specific request, client should have local awareness that some app action should be done only once on server, if for some reason request is processed by server and client does not know anything about it (request failed). This ID will provide server information that it will not repeat action if it was already processed)
X-Auth: (API Key + ":" + HMAC signature, example: 4ebd366d-76f4-4400-a3b6-e51515d054d6:fb8484df7941a4d0c337939a73cc8fc09f50bd3309af5e1926baaee4d5059dfc)

Is this possible / supported with ImportJSONAPI? I have come up with INT((NOW()-25569)*86400) as a means of generating X-Time, but I get an error saying that the function is not allowed to reference a cell that uses NOW(), RAND() or RANDBETWEEN().

Thank you!

SCH00N3R