# US 7,613,872 B2 · Providing core root of trust measurement (CRTM) for systems using a backup copy of basic input/output system (BIOS) > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,613,872 B2 - Document ID: US7613872B2 - Status: Granted - Kind: B2 - Application number: 11/564,096 - Filed: 2006-11-28 - Published: 2008-05-29 - Granted: 2009-11-03 - Earliest claimed: 2006-11-28 - Assignees: International Business Machines Corporation - Inventors: Richard A. Dayan; Scott N. Dunham - Web page: https://patentgrep.com/patent/US7613872B2 ## CPC - G06F 21/575: {Secure boot} - G06F 21/572: {Secure firmware programming, e.g. of basic input output system [BIOS]} - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A flash memory is provided that includes a primary flash bank and a secondary flash bank. The primary flash bank includes CRTM logic and BIOS logic and the secondary flash bank comprises a backup copy of the CRTM logic and the BIOS logic. A switching mechanism is configured to selectively activate the primary flash bank or the secondary flash bank. ## Claims ### Claim 1 A computer system, comprising: a flash memory including a primary flash bank and a secondary flash bank, wherein the primary flash bank comprises Core Root of Trust Measurement (CRTM) logic and Basic Input/Output System (BIOS) logic and the secondary flash bank comprises a backup copy of the CRTM logic and the BIOS logic; and a switching mechanism configured to selectively activate the primary flash bank or the secondary flash bank. ### Claim 2 (depends on 1) The system according to claim 1, wherein the CRTM logic in the primary flash bank and the backup copy of the CRTM logic in the secondary flash bank have lock until reset capability. ### Claim 3 (depends on 2) The system according to claim 2, wherein the CRTM logic in the primary flash bank is configured to lock itself and the backup copy of the CRTM logic in the secondary flash bank before turning control over to another software component and wherein the backup copy of the CRTM logic in the secondary flash back is configured to lock itself and the CRTM logic in the primary flash bank before turning control over to another software component. ### Claim 4 (depends on 1) The system according to claim 1, wherein the BIOS logic in the primary flash bank and the backup copy of the BIOS logic in the secondary flash bank have temporary lock capability. ### Claim 5 (depends on 1) The system according to claim 1, wherein the primary flash bank comprises a CRTM staging area configured to stage a CRTM update with replacement CRTM logic. ### Claim 6 (depends on 5) The system according to claim 5, wherein the CRTM staging area has temporary lock capability. ### Claim 7 (depends on 1) An integrated circuit on a semiconductor on insulator chip comprising the system of claim 1. ### Claim 8 A method for providing Core Root of Trust Measurement (CRTM) within a computer system having a backup copy of Basic Input/Output System (BIOS) logic, comprising: receiving an indication that the computer system is being powered on; selectively activating either a primary flash bank having CRTM logic and BIOS logic stored therein or a secondary flash bank having a backup copy of the CRTM logic and BIOS logic stored therein; passing control of the computer system to the CRTM logic and then the BIOS logic of the selectively activated flash bank; activating the non-selected flash bank in response to the BIOS logic within the selected flash bank failing to execute to completion; and passing control of the computer system to the CRTM logic and then the BIOS logic in the newly activated flash bank. ### Claim 9 (depends on 8) The method according to claim 8, further comprising locking the CRTM logic stored within the primary flash bank and the backup copy of the CRTM logic stored within the secondary flash bank upon completion of executing the CRTM logic. ### Claim 10 (depends on 8) The method according to claim 8, further comprising staging a CRTM update of the CRTM logic within the primary flash bank. ### Claim 11 (depends on 10) The method according to claim 10, wherein the staging of a CRTM update comprises: determining whether a staging area within the primary flash bank contains a valid replacement of CRTM logic; and loading the replacement CRTM logic into memory and passing control of the computer system to the replacement CRTM logic in response to a determination of valid replacement CRTM logic. ### Claim 12 (depends on 11) The method according to claim 11, wherein the determining of a valid replacement of CRTM logic comprises using a public key that is contained within the CRTM logic and validating that the replacement CRTM logic was signed with a private key that associates with the public key. ### Claim 13 (depends on 11) The method according to claim 11, further comprising updating a segment of the primary flash bank that stores the CRTM logic with the valid replacement CRTM logic. ### Claim 14 A computer-readable medium storing computer instructions for providing Core Root of Trust Measurement (CRTM) within a computer system having a backup copy of Basic Input/Output System (BIOS) logic, the computer instructions when executed by the computer system carry out the following steps: receiving an indication that the computer system is being powered on; selectively activating either a primary flash bank having CRTM logic and BIOS logic stored therein or a secondary flash bank having a backup copy of the CRTM logic and BIOS logic stored therein; passing control of the computer system to the CRTM logic and then the BIOS logic of the selectively activated flash bank; activating the non-selected flash bank in response to the BIOS logic within the selected flash bank failing to execute to completion; and passing control of the computer system to the CRTM logic and then the BIOS logic in the newly activated flash bank. ### Claim 15 (depends on 14) The computer-readable medium according to claim 14, further storing instructions for locking the CRTM logic stored within the primary flash bank and the backup copy of the CRTM logic stored within the secondary flash bank upon completion of executing the CRTM logic. ### Claim 16 (depends on 14) The computer-readable medium according to claim 14, further storing instructions for staging a CRTM update of the CRTM logic within the primary flash bank. ### Claim 17 (depends on 16) The computer-readable medium according to claim 16, wherein the staging of a CRTM update comprises: determining whether a staging area within the primary flash bank contains a valid replacement of CRTM logic; and loading the replacement CRTM logic into memory and passing control of the computer system to the replacement CRTM logic in response to a determination that the replacement CRTM logic is valid. ### Claim 18 (depends on 17) The computer-readable medium according to claim 17, wherein the determining of a valid replacement of CRTM logic comprises using a public key that is contained within the CRTM logic and validating that the replacement CRTM logic was signed with a private key that associates with the public key. ### Claim 19 (depends on 17) The computer-readable medium according to claim 17, further storing instructions for locking the CRTM logic in the primary flash bank and the backup copy of the CRTM logic within the secondary flash bank if the replacement CRTM logic is invalid. ### Claim 20 (depends on 17) The computer-readable medium according to claim 17, further storing instructions for updating a segment of the primary flash bank that stores the CRTM logic with the valid replacement CRTM logic.