Recover Encrypted file...

Recover Encrypted file...

How can I recover an encrypted file in Windows XP after formatting?

Please Help me!!!
Chandru KAsked:
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Lee W, MVPTechnology and Business Process AdvisorCommented:
What good is encryption if it's easy to recover without the keys?  If you encrypted the file using the Encrypting File System (EFS) on an XP system and then formatted the drive, you have lost the key and the only way you'll recover that file is by waiting until the technology to break the encryption allows you to do so in a timely manner.  Right now, using today's tech, you're probably looking at months to years of computer time trying to crack it.

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Jose Gabriel Ortega CastroCEO Faru Bonon IT - EE Solution ExpertCommented:
You do need the key of your computer, it's usually a certificate that comes with the system.

So if you encrypt the file using the Windows XP system it has a certificate, then, usually that certificate is your key.
if you didn't get it before formatting, for me it's just lost. That's the whole reason to encrypt it, doesn't it? if anyone could un-encrypt the file what would be the purpose to do so.
Dr. KlahnPrincipal Software EngineerCommented:
Lee is correct.  When the drive was formatted, the encryption key for the file was irretrievably lost -- unless there is a full backup of the previous system.

The Encrypting File System uses information in the system and user profiles, information unique to that computer and that installation of Windows, to generate the encryption key.  Without that information, any encrypted files must be considered irretrievably lost unless quantum decryption becomes a reality ... if it ever does ... that's at least ten years away.

In Windows XP and beyond, the user's RSA private key is backed up using an offline public key whose matching private key is stored in one of two places: the password reset disk (if Windows XP is not a member of a domain) or in the Active Directory (if Windows XP is a member of a domain). This means that an attacker who can authenticate to Windows XP as LocalSystem still does not have access to a decryption key stored on the PC's hard drive.

In Windows 2000, XP or later, the user's RSA private key is encrypted using a hash of the user's NTLM password hash plus the user name – use of a salted hash makes it extremely difficult to reverse the process and recover the private key without knowing the user's passphrase.
Seth SimmonsSr. Systems AdministratorCommented:
No comment has been added to this question in more than 21 days, so it is now classified as abandoned.

I have recommended this question be closed as follows:

-- Lee W MVP (https:#a42519078)
-- Jose Gabriel Ortega C (https:#a42519082)
-- Dr. Klahn (https:#a42519299)

If you feel this question should be closed differently, post an objection and the moderators will review all objections and close it as they feel fit. If no one objects, this question will be closed automatically the way described above.

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