Are you trying to open encrypted files on your computer? Windows typically marks encrypted file or folder names in green instead of plain black text.
Note. If you are reading this post looking for information on decrypting files encrypted with CryptoLocker, it won’t help. You will have to pay the ransom and hope that they actually send you encryption keys.
When encrypting files and folders, Windows will use a self-generated certificate that contains the keys used to encrypt and decrypt data. When you open encrypted data while logging into the user account that generated the certificate, the decryption process is transparent and the files open normally.
However, if another user or system tries to access the same data files, or if the files are moved to a different location, they cannot be opened until the original certificate is installed.
Anyway, about encrypting and decrypting files on Windows, remember that you always need certificates / encryption keys. When you encrypt a file or folder in Windows, encryption keys are automatically generated and associated with your account.
On Windows 7 and later, you will indeed be prompted to back up the encryption key (EFS certificate).
You should definitely do this immediately. If you do not have these encryption keys, you will not be able to decrypt the data. Unfortunately, there is no way around this since the encryption is very secure and cannot be easily broken.
If you can still access the computer on which the data was originally encrypted, you can try exporting the certificate and then importing it to another computer.
EFS certificates backup
There are several ways to back up your file encryption certificates, which I’ll discuss below. The first way is to click “Start” and enter the certificate.
Click Manage User Certificates and this will open the certificates for the current user. On Windows 7, you can also type certmgr.msc and press Enter to open the Certificate Manager.
Now expand “Personal” and click “Certificates”. You should see all certificates listed in the right pane. There can be only one, but if not, then the only certificates you are interested in are those for which the encrypted file system is listed in the Purpose section.
Right-click the certificate, select All Tasks, and click Export.
This will open the Certificate Export Wizard, which is in the same location as you will be if you click the Back Up (Recommended) button when prompted by Windows.
On the next screen, you will want to select Yes, export the private key along with the certificate. If you don’t have the private key, you won’t be able to decrypt any of the encrypted files.
On the next screen, you need to select the format you want to use to export the certificate. Personal information sharing should already be selected and you can leave it by checking only the first checkbox.
Since this certificate contains a private key, you need to password protect it. Check the Password box and enter a strong password.
Finally, click Browse and choose the location where you want to save the file. It is highly recommended not to save the file to the computer itself. If something happens to the PC, then you will lose the key along with it.
Also, give the file a name that is useful to you but not too obvious to others what it is. For example, don’t call it an EFS key like I did below!
Click Next and then Finish. Your personal encryption key is now saved as a file. Now you can take this file and import it to any other Windows computer. The import is really simple. All you have to do is double-click the file and the Certificate Import Wizard will open.
After importing the certificate, you will be able to decrypt any files encrypted with that certificate. As mentioned earlier, if you’re trying to open encrypted files and you don’t have or can’t find the certificate anymore, then those files will mostly disappear.
Some programs claim to be able to decrypt your files for a hefty price, but they never worked for me and therefore I have not listed any of them here. If you have any questions, do not hesitate to leave comments. Enjoy!