Unreadable encrypeted file

[churin]

I found an encrypted file which is not readable now. I know I encrypted
it long times ago but I can not open nor decrypt it. I did not use any
third party encryption software. Could anyone help?

 

[Carey Frisch [MVP]]

Unless you previously made an encryption certificate backup key,
that encrypted file is going to stay encrypted forever.

How to remove file or folder encryption in Windows XP
http://support.microsoft.com/default.aspx?scid=kb;EN-US;308993

--
Carey Frisch
Microsoft MVP
Windows Desktop Experience -
Windows System & Performance

---------------------------------------------------------------

:

I found an encrypted file which is not readable now. I know I encrypted
it long times ago but I can not open nor decrypt it. I did not use any
third party encryption software. Could anyone help?

 

[Patrick Keenan]

I found an encrypted file which is not readable now. I know I encrypted it
long times ago but I can not open nor decrypt it. I did not use any third
party encryption software. Could anyone help?

You need to take it to the account you encrypted it with, or import the
certificates exported from that account, or use the designated recovery
agent.

If you can't do any of those things, then bascically nobody can help. The
data can be regarded as lost.

It's very important if you're going to use EFS, to finish the job of and
back up the certificates and store them safely.

This step is optional, and shouldn't be.

Sorry there isn't better news.

HTH
-pk

 

[churin]

Thanks to Carey and Patrick for your responses.
The post by Carey indicates that if an encryption certificate backup key
is not created encrypted file stays encrypted forever. But when I was
experimenting encryption I never created the certificate but I believe I
could decrypt it.

So, question is why I can no longer decrypt it. Since the encryption was
done, the OS became unbootable and I replaced it by restoring its
backup. I do not remember whether the backup was made before or after
the encyption was done. Could this restoring the OS from its backup be
the cause of the problem?

 

[John Wunderlich]

Thanks to Carey and Patrick for your responses.
The post by Carey indicates that if an encryption certificate
backup key is not created encrypted file stays encrypted forever.
But when I was experimenting encryption I never created the
certificate but I believe I could decrypt it.

So, question is why I can no longer decrypt it. Since the
encryption was done, the OS became unbootable and I replaced it by
restoring its backup. I do not remember whether the backup was
made before or after the encyption was done. Could this restoring
the OS from its backup be the cause of the problem?

Most definately.

When you created your encrypted file system, Windows chose a random
encryption key (Certificate) and encrypted your files to that key. It
then encrypted this key with a combination of your Secure ID (SID),
your password, and who knows what else from your system and stored it
in the system. As long as these things are available to the system, it
can subsequently decrypt your key and then use it to decrypt your
files. When your system crashed, you lost some part of that
information that Windows used to encrypt your certificate so now
Windows itself can not decrypt your key and use it in turn to decrypt
your files.

Had you have made a backup of that certificate/key, you could have re-
installed it into Windows and things would work again. As it is,
nothing can decode that key. Never trust an OS to store encryption
keys. Always make a backup.

HTH,
John

 

[churin]

Most definately.

When you created your encrypted file system, Windows chose a random
encryption key (Certificate) and encrypted your files to that key. It
then encrypted this key with a combination of your Secure ID (SID),
your password, and who knows what else from your system and stored it
in the system. As long as these things are available to the system, it
can subsequently decrypt your key and then use it to decrypt your
files. When your system crashed, you lost some part of that
information that Windows used to encrypt your certificate so now
Windows itself can not decrypt your key and use it in turn to decrypt
your files.

Had you have made a backup of that certificate/key, you could have re-
installed it into Windows and things would work again. As it is,
nothing can decode that key. Never trust an OS to store encryption
keys. Always make a backup.

HTH,
John

Thank you very much for your detailed and enlightening explanation about
file encryption. I will create certificate/key when I encrypt files next
time. Thanks again.

churin