What does Windows error code 808 (ERROR_ENCRYPTED_IO_NOT_POSSIBLE) mean?

ERROR_ENCRYPTED_IO_NOT_POSSIBLE

The read or write operation to an encrypted file could not be completed because the file has not been opened for data access.

ERROR_ENCRYPTED_IO_NOT_POSSIBLE is Win32 error 808 (0x328) and belongs to Encrypted File System data access.

Where the result appears

• A direct read or write against an EFS-protected file.
• Backup software opening encrypted data without normal data access.
• A filter driver or restore utility working with raw encrypted streams.
• An application that opened only metadata or attribute access.

Likely causes

• the file handle lacks read or write data access required for the requested encrypted I/O.
• the caller mixed raw EFS operations with a handle opened for metadata-only work.
• a backup or restore path reused a handle whose desired-access mask is too narrow.
• the file state changed between attribute inspection and the actual data request.

Troubleshooting steps

• Record desired-access flags used when the handle was opened.
• Record whether OpenEncryptedFileRaw or ordinary file I/O was intended.
• Record file attributes, encryption state, and volume filesystem.
• Record the caller identity and availability of the EFS certificate or recovery key.
• Record the exact operation, offset, and byte count that failed.

What to verify

Verify whether the file handle lacks read or write data access required for the requested encrypted I/O. Check desired-access flags used when the handle was opened together with whether OpenEncryptedFileRaw or ordinary file I/O was intended.

Handling, retry, and recovery

Close the unsuitable handle and reopen the file with the access required by the chosen EFS API. A retry with the same metadata-only handle is deterministic and should not be looped.

Difference from nearby codes

It is about how the file was opened, not proof that ciphertext is corrupt or that the user lacks every EFS key.

Practical example

A backup agent enumerates attributes with a low-privilege handle and later tries to read encrypted file data through that same handle.

References

• Microsoft: System Error Codes (500–999) — reference for error 808.
• Microsoft: Encrypted File System — reference for error 808.
• Microsoft: Encrypting File System overview — reference for error 808.