Hi everyone, I am currently trying to write the ChangeKey command implementation in Javascript. I ran into a few blockers & questions, and would like some clarification & help. I've read through both the Product Data Sheet & Application Note, and here is where I am stuck at:
1. How is Step 15 derived? My assumption (based on purely looking at related values) is that the Input for CMAC is made up of: Change Key Command (INS) || CmdCtr || TI || Value from Step 12
Is this assumption correct? Where did C4 come from?
2. Even using values from Table 26, I cannot get the value for Step 17. I attempted to generate a CMAC using the IV for CMACing as the CMAC key and the Input for CMAC as the value itself. This is most definitely wrong, as I cannot get the correct values. What values do I CMAC together to get the value in Step 17, and how is the IV for CMACing used?
Thank you!
