9–72
Chapter 9: Configuration, Design Security, and Remote System Upgrades in the Cyclone III Device Family
Design Security
Table 9–24. Security Key Features (Part 2 of 2)
Volatile Key Features
Description
Secure against copying, reverse engineering, and
tampering
Design protection
Note to Table 9–24:
(1) Key programming is carried out using the JTAG interface.
AES volatile key zeroization is supported in Cyclone III LS devices. The volatile key
clear and key program JTAG instructions from the device core is supported to protect
Cyclone III LS devices against tampering. You can clear and reprogram the key from
the device core whenever tampering attempt is detected by executing the
KEY_CLR_VREG and KEY_PROG_VOLJTAG instructions to clear and reprogram the
volatile key, and then reset the Cyclone III LS device by pulling the nCONFIGpin low
for at least 500 ns. When nCONFIGreturns to a logic-high level and nSTATUSis released
by the Cyclone III LS device, reconfiguration begins to configure the Cyclone III LS
device with a benign or unencrypted configuration file. After configuration is
successfully completed, observe the cyclecompletesignal from error detection block
to ensure that reconfigured CRAM bits content is correct for at least one error
detection cycle. You can also observe the cyclecompleteand crcerrorsignals for any
unintentional CRAM bits change.
f
cyclecompleteis a signal that is routed from the error detection block to the core for
the purpose of every complete error detection cycle. You must include the
cycloneiiils_crcblockWYSIWYG atom in your design to use the cyclecomplete
signal. For more information about the SEU mitigation, refer to the SEU Mitigation in
Cyclone III Devices chapter.
V
CCBAT is a dedicated power supply for the volatile key storage and not shared with
other on-chip power supplies, such as VCCIO or VCC. VCCBAT continuously supplies
power to the volatile register regardless of the on-chip supply condition. The nominal
voltage for this supply is 3.0 V, while its valid operating range is from 1.2 to 3.3 V. If
you do not use the volatile security key, you may connect the VCCBAT to a 1.8-V, 2.5-V,
or 3.0-V power supply.
1
1
After power-up, wait for 200 ms (Standard POR) or 9 ms (Fast POR) before beginning
the key programming to ensure that VCCBAT is at its full rail.
As an example, BR1220 (-30°C to +80°C) and BR2477A (-40 C to +125°C) are lithium
coin-cell type batteries used for volatile key storage purposes.
f
For more information about the battery specifications, refer to the Cyclone III LS Device
Data Sheet chapter.
Cyclone III LS Design Security Solution
Cyclone III LS devices are SRAM-based devices. To provide design security,
Cyclone III LS devices require a 256-bit volatile key for configuration bitstream
encryption.
Cyclone III Device Handbook
Volume 1
August 2012 Altera Corporation
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