What does HRESULT 0x803100AA (FVE_E_PASSPHRASE_TOO_LONG) mean?

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Description:

The password cannot exceed 256 characters.

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FVE_E_PROTECTOR_CHANGE_PASSPHRASE_MISMATCH	FVE_E_NO_PASSPHRASE_WITH_TPM

FVE_E_PASSPHRASE_TOO_LONG

Where the operation stops

The value 0x803100AA, named FVE_E_PASSPHRASE_TOO_LONG, is returned when the proposed BitLocker password exceeds the maximum supported length of the protector interface. It belongs to the key-protector lifecycle part of BitLocker rather than to generic file I/O.

Note: Never capture PINs, passwords or recovery passwords in logs. When diagnosing this result, remember: IDs, types, policy, call result and attempt counters are sufficient for most diagnosis. Note: A BitLocker key protector wraps access to the volume master key. When diagnosing it, remember: TPM, TPM+PIN, startup key, recovery password, password, certificate and Network Unlock protectors have different volume and policy rules; changing one is not the same as decrypting the volume.

Question	What to verify
Which object failed?	The exact volume GUID, protector GUID, certificate or API target supplied by the caller.
Which state matters?	character count, encoding path, UI versus API call, drive type and effective password policy without collecting the secret.
What is the nearest false lead?	a password rejected for simplicity, FIPS policy or unsupported OS-volume use.

Build a minimal diagnostic record

record character count, encoding path, UI versus API call, drive type and effective password policy without collecting the secret. Keep the full HRESULT and the first method that returned it because later cleanup calls can report a different state.
capture manage-bde -status and the protector inventory for the exact volume GUID, not only the drive letter, because letters can change in WinRE, clusters and deployment environments.
Export BitLocker operational events for the result failure and note the boot session, caller identity and management source; that evidence separates this BitLocker condition from a generic access or storage error.

Change only the failed prerequisite

choose a compliant password at or below the documented limit and verify the calling application is not adding hidden characters. Collect a fresh state snapshot and issue a single retry from the same management layer.

manage-bde -protectors -get C:\npowershell -NoProfile -Command "Get-BitLockerVolume C: | Format-List KeyProtector,ProtectionStatus,VolumeStatus"

Do not delete all key protectors, clear a TPM, reformat a partition or decrypt the volume as a generic response to this result; those actions affect different trust layers and can destroy the easiest recovery route.

Count the value delivered to the API

Applications can add hidden carriage returns, nulls or normalization changes when a password is copied from a vault or text control. Measure the character sequence passed to the BitLocker provider without logging its content. The visible number of characters in a UI can differ from the actual BSTR or PowerShell string length.

Shorten the secret within policy and interface limits, then test one controlled add or change operation. Repeated submissions do not improve a length violation and can trigger separate throttling.

State checks specific to the result

Checkpoint	How to interpret it for it
Before the call	Record the target identity and the pre-call key-protector lifecycle state. The decisive boundary is that the proposed BitLocker password exceeds the maximum supported length of the protector interface.
At failure	Preserve character count, encoding path, UI versus API call, drive type and effective password policy without collecting the secret. This proves whether this result came from BitLocker itself or from a wrapper translating another result.
After correction	Choose a compliant password at or below the documented limit and verify the calling application is not adding hidden characters. The request should then advance without removing an unrelated recovery route.
After reboot or remount	Recheck protection, conversion and lock state for it; a successful management call is incomplete if the next boot cannot unlock the volume.

Verification after the change

Success means more than the absence of a dialog. Confirm that the condition represented by this result now matches the intended design, that the protector inventory has not lost an independent recovery route, and that the next reboot or remount can unlock the volume. If the request advances to another HRESULT, record both values in order because that transition reveals the next unmet prerequisite.

Official documentation

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