https://devzone.nordicsemi.com/f/nordic-q-a/74620/i-m-curious-about-the-mode-of-encryption-aesHello I&#39;m going to use AES for encryption and decryption testing of data this time. Looking at the example of SDK, there are several AES modes, can you tell me the difference between them? And when I say that I send encrypted data to the app, doesen-USTelligent Community 13Fri, 30 Apr 2021 15:19:53 GMThttps://devzone.nordicsemi.com/thread/307707?ContentTypeID=1Fri, 30 Apr 2021 15:19:53 GMT137ad170-7792-4731-bb38-c0d22fbe4515:326c2bdc-4efb-4de9-bfb5-33b5d499df1dVidar Berg<p>Hello,</p> <p>I&#39;d suggest you take a look at the wikipedia page <a href="https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation">here</a>. It provides a good explanation of the different operation modes you can use. </p> [quote user=""]And when I say that I send encrypted data to the app, does the app proceed with data decryption?[/quote] <p>&nbsp;It depends on your implementation. Data will be decrypted before it reaches the application if you use link encryption in our Bluetooth examples. You could also have an application where the data is encrypted/decrypted at application layer like discussed here: <a href="https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/intro-to-application-level-security-using-the-ecb-">https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/intro-to-application-level-security-using-the-ecb-</a> </p><div style="clear:both;"></div>