Security level inconsistencies in AN 556 and Quartus 18 - Security level inconsistencies in AN 556 and Quartus 18 Hello, It looks like there is some inconsistencies about the security levels listed in the Application Note 556/Qcrypt tool and Quartus 18. This is what AN 556/Qcrypt says: The values [0:3] specify increasing levels of security as follows: 0: The security feature is not enabled (unless by the OTP fuse option). 1: The security feature is enabled from the start of the current full or PR configuration until the start of the next full configuration. 2: The security feature is enabled until the next Power-On-Reset event. Furthermore, configuration will not proceed if any action normally prevented by this security feature has taken place since the last Power-On-Reset event. 3: Configuration will not proceed unless the security feature has been permanently enabled by blowing the corresponding fuses in the device. This is what Quartus 18 says: Off (unless by the OTP fuse option) Turns on until the next full configuration Turns on until the next Power-On Reset event Turns on by blowing the corresponding fuses In my understanding, level 3 in AN 556/Qcrypt does not match the description given in Quartus 18. AN 556/Qcrypt level 3 implies it will not enable the option by blowing a fuse (it will only check if it's already blowed but not actually blow it), while Quartus 18 implies it will blow the fuse. So which one is correct? Or are they unrelated options but level 0 to 2 are coincidentally the same? Thanks Replies: Re: Security level inconsistencies in AN 556 and Quartus 18 Hi, The Quartus descriptions are the same as the app note, just they are shorter. For level 3, the configuration will not happen unless the fuse is blown up. This means that when level 3 is selected, the fuses are first checked. If already blown, then the configuration proceeds else not. Simply putting the security level as 3 does not blow up the fuses. Regards