2 posts tagged tf-a, newest first.
TF-A verifying the next stage against a certificate chain inside the FIP — software, on blank fuses, refusing for real. Flipping one bit produced EAUTH on BL33 and a clean halt. Plus the honest limits of what that proves.
Secure boot on this chip comes down to 32 bytes in one-time-programmable memory, and a bit you can never un-blow. I started the project with a rule forbidding its own last step — and three of the four links in the chain turn out to enforce for real on completely blank silicon.