The order based issuance flow is different from pre-authorization in that users tell upfront which identifiers they want a future certificate to contain and the CA responds with a set of authorizations to satisfy. Similar to pre-authorization where users start with Client's Authorize method, fulfill challenges and then call GetAuthorization or WaitAuthorization, the order based flow starts with AuthorizeOrder and then GetOrder or WaitOrder. Once all order authorizations are satisfied, users can call CreateOrderCert, as opposed to the old CreateCert, and FetchCert as before. The new method implementation and updates to the existing methods is in golang.org/cl/194379. More on order based flow can be found in https://tools.ietf.org/html/rfc8555#section-7.4. Updates golang/go#21081 Change-Id: I37c37203b50785d7681f65f815d7b19d9c15b96d Reviewed-on: https://go-review.googlesource.com/c/crypto/+/192779 Run-TryBot: Alex Vaghin <ddos@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Filippo Valsorda <filippo@golang.org>