19.2.5.1 6th Vector Format
When the AUTH_MODE field is cleared in the Secure Boot Configuration Packet, the sixth entry of the Arm exception vector table stores the size of the boot file in bytes, including the 16 bytes of its AES-CMAC signature.
When the AUTH_MODE field is set to 1 in the Boot Configuration word, the sixth entry of the Arm exception vector table stores both the size of the boot file including its RSA signature and the size of the X.509 certificate chain. The size of the RSA signature is also encoded.
| Bit | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | |
| CERTIFICATE_SIZE[12:5] | |||||||||
| Access | |||||||||
| Reset | |||||||||
| Bit | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | |
| CERTIFICATE_SIZE[4:0] | SIG_CODE[1:0] | BT_SIZE[16] | |||||||
| Access | |||||||||
| Reset | |||||||||
| Bit | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | |
| BT_SIZE[15:8] | |||||||||
| Access | |||||||||
| Reset | |||||||||
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| BT_SIZE[7:0] | |||||||||
| Access | |||||||||
| Reset | |||||||||
Bits 31:19 – CERTIFICATE_SIZE[12:0] Size of the of X.509 certificate chain, in bytes
Bits 18:17 – SIG_CODE[1:0] Code for the RSA signature length
| Value | Description |
|---|---|
| 00 | 2048 bits |
| 01 | 3072 bits |
| 10 | 4096 bits |
| 11 | RFU |