I have some files on an NTFS USB drive. The files were encrypted on a Windows 10 pc and copied to the USB.

I had to completely reinstall Windows on the PC. I do not have a backup of the USB files

I know the name of the PC, and the username and password.

Is it possible to regain access to the files on the USB?

I can take ownership and list the contents of the drive and folders but i can't open the files.

  • 1
    Do you have any other files? Apparently you need to export the certificate from the original computer in order to decrypt them. Source.
    – user
    Commented Jul 23, 2020 at 16:26
  • 1
    @user That should probably be an answer, not a comment :)
    – vidarlo
    Commented Jul 23, 2020 at 17:31
  • How were they encrypted? Natively Windows uses EFS however there are third party programs that use their own technique for file encryption.
    – phbits
    Commented Jul 23, 2020 at 17:38

1 Answer 1


Provided you are using the native in-line encryption provided by Windows, the only way to recover them is to obtain a copy of the original encryption keys. These are notably not based on your password/PIN (though they are encrypted by a master password secured by your login credentials). Windows provides an option to export these security keys in PKCS#12 format for backup purposes (and will usually nag you about backing them up until you either do so or explicitly turn off the nag notifications).

Without these encryption keys, there is no realistic way you can recover the file contents, as the encryption methods used are sufficiently secure to protect against most attacks.

Unfortunately, as you reinstalled Windows 10, you no longer have access to these keys unless you had previously backed them up somewhere else.

  • It sounds like im screwed. I was a bit dumb. I hadn’t realised when I copied the files that they were encrypted. The files I was copying included the pks file. I kept a record of the password in lastpass but not the post file itself.
    – Adam
    Commented Jul 24, 2020 at 20:52

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