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
Bits 16:0 – BT_SIZE[16:0] Boot file size, in bytes
The online versions of the documents are provided as a courtesy. Verify all content and data in the device’s PDF documentation found on the device product page.
