From 70ccde012bbfe18d8e851d1781b545128fb04403 Mon Sep 17 00:00:00 2001 From: Justin Hall Date: Fri, 26 Apr 2019 12:01:24 -0700 Subject: [PATCH] Update switch-pcr-banks-on-tpm-2-0-devices.md edits --- .../tpm/switch-pcr-banks-on-tpm-2-0-devices.md | 2 ++ 1 file changed, 2 insertions(+) diff --git a/windows/security/information-protection/tpm/switch-pcr-banks-on-tpm-2-0-devices.md b/windows/security/information-protection/tpm/switch-pcr-banks-on-tpm-2-0-devices.md index 25e1754f08..5493d4428d 100644 --- a/windows/security/information-protection/tpm/switch-pcr-banks-on-tpm-2-0-devices.md +++ b/windows/security/information-protection/tpm/switch-pcr-banks-on-tpm-2-0-devices.md @@ -57,6 +57,7 @@ A TPM can be configured to have multiple PCR banks active. When BIOS is performi - Registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\IntegrityServices
- DWORD: TPMActivePCRBanks
- Defines which PCR banks are currently active. This is a bitmap defined in the TCG Algorithm Registry.
+ Windows checks which PCR banks are active and supported by the BIOS. Windows also checks if the measured boot log supports measurements for all active PCR banks. Windows will prefer the use of the SHA-256 bank for measurements and will fall back to SHA1 PCR bank if one of the pre-conditions is not met. You can identify which PCR bank is currently used by Windows by looking at the registry. @@ -64,6 +65,7 @@ You can identify which PCR bank is currently used by Windows by looking at the r - Registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\IntegrityServices
- DWORD: TPMDigestAlgID
- Algorithm ID of the PCR bank that Windows is currently using. (For the full list of supported algorithms, see the TCG Algorithm Registry.)
+ Windows only uses one PCR bank to continue boot measurements. All other active PCR banks will be extended with a separator to indicate that they are not used by Windows and measurements that appear to be from Windows should not be trusted. ## Related topics