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Having "credentials" on ACVTS Prod means having the signed certificate referred to in Step 5 under Accessing ACVTS Prod on How to Access ACVTS. This gives the user access to the ACVTS Prod server. We use the terms "credentials", "certificate" and "access to" interchangeably in this sense.
"Authorization" refers to permission to perform validations for a particular Approved security function (i.e., algorithm) on ACVTS Prod. Authorization for a particular security function is achieved by running though certification in the Demo environment.
No. A CST lab only needs to be authorized for one Approved security function (algorithm) in order to get a certificate (credentials) on ACVTS Prod. Authorization for additional Approved security functions can be added as needed.
1 January 2020 is the start date for a six month period (until 30 June 2020) for which a certificate on ACVTS Prod is required in order for CAVS submissions to be processed. It is not a deadline.