Intel IA-32 Manuale Utente

9-40 Vol. 3A

The extended signature table is a structure that may be appended to the end of the encrypted data
when the encrypted data only supports a single processor signature (optional case). The
extended signature table will always be present when the encrypted data supports multiple
processor steppings and/or models (required case). 

The extended signature table consists of a 20-byte extended signature header structure, which
contains the extended signature count, the extended processor signature table checksum, and 12
reserved bytes (Table 9-8). Following the extended signature header structure, the extended
signature table contains 0-to-n extended processor signature structures.

Each processor signature structure consist of the processor signature, processor flags, and a
checksum (Table 9-9). 

The extended signature count in the extended signature header structure indicates the number of
processor signature structures that exist in the extended signature table.  

The extended processor signature table checksum is a checksum of all DWORDs that comprise
the extended signature table. That includes the extended signature count, extended processor
signature table checksum, 12 reserved bytes and the n processor signature structures. A valid
extended signature table exists when the result of a DWORD checksum is 00000000H.

Processor Signature[n] 

Data Size 
+ 68 + 
(n * 12)

Processor Flags[n]

Data Size 
+ 72 + 
(n * 12)

Checksum[n] 

Data Size 
+ 76 + 
(n * 12)

Extended Signature Count ‘n’

Data Size + 48

Extended Processor Signature Table Checksum

Data Size + 52

Reserved (12 Bytes)

Data Size + 56

Processor Signature[n] 

Data Size + 68 + (n * 12)

Processor Flags[n]

Data Size + 72 + (n * 12)

Checksum[n] 

Data Size + 76 + (n * 12)