A decryption error usually means your computer lacks the key or permission to read an encrypted file, and the fix depends on where the encryption came from.

When Windows or macOS tells you it cannot decrypt a file, the most common cause is that you are trying to open something encrypted with a password or security certificate your current user account does not have. This is different from a corrupted file — the file itself is intact, but your computer is locked out of reading it. The solution ranges from entering the correct password to recovering a lost encryption key, depending on how the file was encrypted in the first place.

Decryption errors happen most often with files protected by BitLocker (Windows), FileVault (Mac), password-protected archives, or files encrypted with a work security certificate. Each type requires a different recovery path, and some are faster than others.

Key Takeaways

  • Check whether the file is encrypted by BitLocker, FileVault, a password, or a work certificate — the recovery method changes for each one.
  • If you encrypted the file yourself and forgot the password, recovery is difficult or impossible without the original password or recovery key.
  • BitLocker and FileVault both generate recovery keys when first enabled — finding that key is usually the fastest path to decryption.
  • Work files encrypted with a company certificate require your IT department to restore your access or provide a recovery certificate.
  • If the file is corrupted rather than locked, decryption will fail even with the correct key, and you may need to restore from a backup.

Identify which encryption method locked the file

Before you can fix the problem, you need to know what encrypted the file. Right-click the file and select Properties (Windows) or Get Info (Mac). Look for a lock icon, a "Encrypted" label, or a note about the file being protected. If you see nothing obvious, the encryption may be at the folder or drive level rather than on the individual file.

On Windows, if the entire drive or a folder is encrypted, you will see BitLocker in Settings under System > About > Device encryption or Manage BitLocker. On Mac, check System Settings > Privacy & Security > FileVault. If neither of those is on, the file was likely encrypted with a password, a work certificate, or a third-party tool.

Recover a BitLocker recovery key on Windows

If your Windows drive is encrypted with BitLocker and you cannot decrypt a file, the issue is usually that your user account lost access to the drive itself. BitLocker generates a 48-digit recovery key when it is first turned on. If you saved that key, you can use it to regain access.

Look for the recovery key in these places, in order: your Microsoft account (sign in at account.microsoft.com and search for "BitLocker"), a printed copy you may have kept, a USB drive you created during setup, or your work IT department if this is a company device. If you find the key, restart your computer, enter the recovery key when prompted, and the drive will unlock.

If you cannot find the recovery key and you are the only person who set up BitLocker, you may not be able to decrypt the drive without professional data recovery, which is expensive. If this is a work computer, contact your IT department — they often have a copy of the recovery key on file.

Unlock a FileVault-encrypted Mac

On a Mac, FileVault encryption is usually tied to your login password. If you can log in to your Mac, FileVault is already unlocked for you. If you cannot log in, or if you see a message that FileVault is preventing access to a specific file, you need the recovery key that was generated when FileVault was turned on.

To find your FileVault recovery key, log in with your Apple ID at iforgot.apple.com, or check any printed or digital copy you saved when FileVault was first enabled. If you have the key, restart your Mac and enter it at the FileVault unlock screen. If you do not have the key and cannot reset your Apple ID password, contact Apple Support — they can verify your identity and help you regain access.

Decrypt a password-protected file or archive

If the file is a ZIP, RAR, or 7Z archive, or a document encrypted with a password, you need the original password to open it. There is no way around this — if you do not remember the password, the file cannot be decrypted without specialized (and expensive) password-cracking tools, and even those do not always work.

If you think you know the password but keep getting an error, make sure Caps Lock is off and that you are not accidentally including extra spaces. Some password managers (like 1Password or Bitwarden) store passwords for encrypted files — check there before you assume the password is lost. If you have a backup of the file from before it was encrypted, restore that instead.

Restore access to work-encrypted files

Files encrypted with a work security certificate or your company's encryption tool require your IT department to restore your access. This usually happens when you change jobs, lose a device, or your certificate expires. Contact your IT helpdesk and tell them you cannot decrypt a work file. They can either re-issue your certificate, provide a recovery certificate, or decrypt the file on their end and send it back to you.

Do not try to remove the encryption yourself — work files are encrypted for security reasons, and bypassing that can violate company policy. The IT department can usually restore access within a few hours.

Distinguish between a locked file and a corrupted one

Sometimes a file will not decrypt because it is corrupted, not because you lack the key. If you have the correct password or recovery key but still get an error, the file may be damaged. Try opening it on a different computer or in a different program — if it fails everywhere, corruption is likely.

If you have a backup of the file from before it was corrupted, restore that. If not, professional data recovery services can sometimes repair corrupted encrypted files, but the cost is high and success is not may provide. For important files, always keep a backup in a separate location.

Frequently Asked Questions

Can I decrypt a file without the password?

Not without specialized tools, and those are expensive and do not always work. If you encrypted the file yourself, your best option is to restore an unencrypted backup. If it is a work file, contact your IT department — they may have a recovery option.

What if I have the recovery key but it does not work?

Make sure you are entering it exactly as written, with no extra spaces or dashes. If it still fails, the key may be for a different drive or file. Try the key on a different computer, or contact the person or department that issued it to confirm it is the right one.

Is there a way to recover a lost BitLocker recovery key?

If you saved it to your Microsoft account, you can retrieve it online. If you printed it or saved it to a USB drive, look in those places. If it is truly lost and you are not on a work network, professional data recovery is the only option.

Why does my Mac ask for a FileVault recovery key when I know my password?

This usually means your login password changed but your FileVault password did not sync. Use your recovery key to unlock the drive, then go to System Settings and update your FileVault password to match your current login password.

Can my IT department decrypt files I encrypted myself?

No, not without the password or recovery key. If you encrypted a work file with your own password and lost it, your IT department cannot help you recover it. They can only help with files encrypted by company tools or certificates.