Patent ID: 11921858
Assignee: DELL PRODUCTS L.P.
Field: Computer technology (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 6:
7. A method for protecting against alterations in chain sequencing in an information handling system, the information handling system comprising a BIOS memory medium storing a set of BIOS instructions executable to transition control between entities in a sequence, the method comprising:
storing, in a memory medium in a root of trust for the information handling system, a chain of trust database comprising a set of chains of trust, wherein each chain of trust specifies a plurality of entities in a sequence originating from the root of trust;
in response to an instruction to start a boot process of a plurality of boot processes:
1) selecting, by the root of trust, a chain of trust from the chain of trust database corresponding to the boot process;
2) verifying, by the root of trust, a first entity in the selected chain of trust;
3) storing, in the root of trust memory medium, a root of trust identifier as a previous entity identifier;
4) setting, by the root of trust, a sequence count to zero;
5) sending, by the BIOS, a next entity identifier to the root of trust,
6) receiving, by the root of trust, the next entity identifier;
7) incrementing, by the root of trust, the sequence count;
8) retrieving, from the root of trust memory medium, by the root of trust, based on the sequence count and the selected chain of trust, a correct transition link between the previous entity identifier and the next entity identifier;
9) comparing, by the root of trust, the received next entity identifier with the stored next entity identifier based on the sequence count;
10) notifying, by the root of trust, the BIOS if the received next entity identifier matches the stored next entity identifier;
11) Determining, by the BIOS, if the sequence count received from the root of trust is valid;
12) Transitioning control to an entity corresponding to the received next entity identifier; and

repeating steps 5-12 until the BIOS transitions control to a last entity in the sequence.