【应用手册】AN 589: Using the Design Security Feature in Cyclone III LS Devices This application note describes the design security feature in Cyclone® III LS devices. The design security feature is able to decrypt a configuration bitstream using an industry standard 256-bit advanced encryption standard (AES) key and AES encryption algorithm to protect your designs from the following unauthorized activities: ■ Copying ■ Reverse engineering ■ Tampering The following design features make the solution secure: ■ Cyclone III LS devices do not support configuration file read back. This prevents attempts to read back the configuration file after it is decrypted. ■ Two user-defined 256-bit sequences are required to generate the 256-bit AES key. ■ The volatile 256-bit AES key is stored in the Cyclone III LS device and cleared when the external battery is removed. ■ Depending on the security mode, you can configure the Cyclone III LS device using a configuration file that is encrypted with the same key, or configure with a normal configuration file for board level testing. AN 589: Using the Design Security Feature in Cyclone III LS Devices September 2009 AN-589-1.0 This application note describes the design security feature in Cyclone III LS devices. The design security feature is able to decrypt a configuration bitstream using an industry standard 256-bit advanced encryption standard (AES) key and AES encryption algorithm to protect your designs from the following unauthorized activities: ■ C……