TMS320F28384D: Reagarding Secure Boot

Gayathri GP said:

Regarding the secure flash boot feature present on TMS320F2838x devices, Does a CMAC-based secure boot offer good security?

“good” is a very qualitative word. CMAC is an industry standard.

Gayathri GP said:

How do you ensure that the keys are not stolen or misused?

They are stored in OTP, which is secure. 

Gayathri GP said:

If I purchase this development board, what level of security will I get?

The security level is not dependent on the board (or the device) but the strength of the CMAC algorithm itself.

You may find www.ti.com/lit/SPRACT3 to be useful.