Try This: Calculate the Benefit of Access Control

Recall Security Step 7 that ChatGPT recommended at the start of this activity:

• 7. Access Control and Isolation:
  Utilize micro:bit’s communication features such as channel, group, and address settings to restrict communication to specific devices or groups. This helps isolate the micro:bit from unauthorized interactions, enhancing the overall security of script updates.

Since the radio has 84 options and XOR has 256 possible ciphers, how many tries maximum would it take to brute force attack this script transfer system?  To find out, simply multiply the possibilities of both. 

• Calculate channel options x cipher options:
  • Answer: 84 x 256 = 21,504

Channel is only one way to make it more difficult for one micro:bit to monitor another.  The micro:bit also has group and address settings that give even more combinations.  So, security could be increased as follows:  

• Channel: 0 to 83 (84 options)
• Group: 0 to 255 (256 options)
• Address: 0 to 4,294,967,295 (232 options)
• XOR cipher: 0 to 255 (256 options)

• How many different combinations would a brute force have to go through to if group settings are added to the script?
  • Answer: channels x groups x XOR options = 84 x 256 x 256 = 5,505,024
• How many different combination would a brute force attack have to try now?  Multiply them all together and see.

Note:  After several attempts to get AI to supply the correct answer with a minimum of back-and-forth, it turned out to be a time saver for a human to make the calculations and write this.