Cyclon 5 tampering protection bit

This is a well-known situation with Cyclone V non-volatile key programming. Once the non-volatile key has already been burned into the OTP fuses, any subsequent attempt to re-run the full key programming sequence (including the key write itself) will fail with that "Non-volatile key programming already attempted" error — because OTP fuses are one-time programmable.

You still can program the tamper-protection bit separately, without re-programming the key.

Program the tamper-protection bit independently using a .jam file

When programming the design security key with a .jam file that has been converted from an Encryption Key Programming file (.ekp) that contains the tamper-protection bit programming instruction, add the switch -eDO_KEY_SECURE to your programming command if programming of the tamper-protection bit is desired.

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

Key points on the -eDO_KEY_SECURE switch

Use quartus_jli with your .jam file and append -eDO_KEY_SECURE to the command line. This instructs the JAM player to execute the tamper-protection bit programming instruction without attempting to re-burn the key fuses.

Note that the tamper-protection bit is one-time programmable and is irreversible.

Enabling the tamper protection bit disables the test mode in Cyclone V devices and disables programming through the JTAG interface. This process is irreversible and prevents Altera from carrying out failure analysis. Cyclone V Device Handbook Volume 1: Device Interfaces and Integration