https://devzone.nordicsemi.com/f/nordic-q-a/35997/debug-the-app-with-the-secure-bootloaderHi, I&#39;ve tried to implement in my project the OTA DFU based on the dfu buttonless example using the secure bootloader. I used this guide to realize it: https://devzone.nordicsemi.com/b/blog/posts/getting-started-with-nordics-secure-dfu-bootloader en-USTelligent Community 13Tue, 03 Jul 2018 08:36:40 GMThttps://devzone.nordicsemi.com/thread/138696?ContentTypeID=1Tue, 03 Jul 2018 08:36:40 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e4bef6d4-7576-4530-91b8-ae4b2591d416Hung Bui<p>Hi Fabiano,&nbsp;</p> <p>&nbsp;</p> <p>You are correct. The bootloader check the CRC of the application image on every booting up to verify the integrity of the application. If you modify the application and flash it with Keil, the CRC wouldn&#39;t be updated and won&#39;t match with your new application. For development you can just skip the CRC check as you already done. But consider to put it back when you release.&nbsp;</p><div style="clear:both;"></div>