This is a software AES test I have written for many MCUs, this time targeting the RAK811 – an STM32L151CBU6 + LoRa SX1276. Which is important in this case, since I am generating the Iv and the key, in the first part of the test, with LoRa's TRNG feature. This requires my LoRandom library and Sandeep Mistry's LoRa library. You have to use both libraries, because despite numerous PR, Sandeep refused to update his library with a working Random function. His is fubared, because he never read the docs...
THIS is not how random works in LoRa...
byte LoRaClass::random() {
return readRegister(REG_RSSI_WIDEBAND);
}Aaaaanyway. Once you have LoRandom installed, you have a real RNG function, and you can generate random passphrases, IVs, etc. The second part of the test is adapted from a standard STM32Cube example, and tests AES 128 ECB and CBC. It checks the validity of the operations – in the first part of the test it is easy to do so visually, because it is plain text. Less so in the second part.
