What does HRESULT 0x803100A7 (FVE_E_KEY_LENGTH_NOT_SUPPORTED_BY_EDRIVE) mean?

 
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FVE_E_KEY_LENGTH_NOT_SUPPORTED_BY_EDRIVE

Why this is not a generic disk error

The practical meaning of FVE_E_KEY_LENGTH_NOT_SUPPORTED_BY_EDRIVE is that the self-encrypting drive cannot use the authentication key length required by BitLocker for hardware encryption. The HRESULT is 0x803100A7.

Three decisions before remediation

Is the result target correct?
Use the volume or protector GUID and confirm its role; do not rely only on a drive letter or friendly name.
Is the result request allowed?
Resolve effective policy, Windows edition, caller token and management source for the hardware-encrypted drive negotiation operation.
Is the result state stable?
Record conversion, protection, lock and reboot status before modifying anything.

Hardware-encrypted drives add firmware, storage-driver and drive-security state below the normal BitLocker volume provider. BitLocker can reject the hardware path before conversion starts, and policy may or may not permit a fallback to software encryption. If policy permits software fallback, verify the final method explicitly. A failed hardware dry run can otherwise leave an administrator assuming protection that never started.

Why a common workaround is wrong

This should not be diagnosed as a missing eDrive capability or policy disallowing hardware encryption; the drive was considered but key parameters are incompatible. That nearby condition needs a different corrective action and may produce a similar user-facing message.

Confirm the returning layer

  • Record drive model/firmware, hardware-encryption status, supported key sizes, storage driver, policy algorithm and dry-run result.
manage-bde -status
powershell -NoProfile -Command "Get-CimInstance -Namespace root/cimv2/security/MicrosoftVolumeEncryption -Class Win32_EncryptableVolume"

State checks specific to FVE_E_KEY_LENGTH_NOT_SUPPORTED_BY_EDRIVE

StageHow to interpret it
Before the callRecord the target identity and the pre-call hardware-encrypted drive negotiation state. The self-encrypting drive cannot use the authentication key length required by BitLocker for hardware encryption.
At failurePreserve drive model/firmware, hardware-encryption status, supported key sizes, storage driver, policy algorithm and dry-run result.
After correctionUpdate supported firmware or use BitLocker software encryption; do not weaken key requirements to fit the device.

References


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