When can the anti-tamper bit be programmed into an Altera device that supports the design security feature?

Description

You can program the anti-tamper bit into an Altera® device whilst the design security key is being programmed, or some time after the design security key has been programmed. In the latter case, the encryption key programming file (.ekp) is not required.
It is also technically possible to program the anti-tamper bit before the design security key has been programmed, but this will render the device unusable. Hence it is recommended to verify that a key has been programmed into the device prior to programming the anti-tamper bit.