How to Decrypt Encrypted Windows Files

I’ve previously written several articles on how to encrypt data on your PC for security reasons, but I’ve really never written about decrypting that data. The reason I have not written any article is because even when you encrypt files on your computer, they are normally transparently decrypted for you when you view them on the same PC.

So when do you really need to decrypt files in Windows? Really only when you move the files to another computer or reformat your current computer and then copy the encrypted data back onto the new computer.

In either case, one thing you have to remember about encrypting and decrypting files in Windows is that you always need your encryption certificates/keys. When you turn on Encrypting File System in Windows, encryption keys are automatically created and associated with your user account.

If you reformat a computer or move the files to another computer, you first have to export the encryption keys in order to regain access to the encrypted data.

If you do not have these encryption keys, you will not be able to decrypt the data. Sadly, there is no way around it, the encryption is very strong and cannot be broken.

If you can still open the files on a computer, you want to make sure to you create a backup of the encryption keys in case the operating system ever fails and you have to copy the data to an external drive.

You can do this by following these steps:

1. Click on Start, then Run and type in mmc.exe.

2. Click on File and then Add/Remove Snap-in

3. Click on the Add button and choose Certificates from the list

4. Choose My user account and then click Finish, then Close and then OK to get back to the Console Root. Now in the tree view, expand Certificates – Current User, then Personal, then Certificates.

I do not have EFS enabled and that’s why I don’t have a Certificates folder under Personal.

5. Now on the right-hand side, you will see certificates listed with an Intended Purpose of Encrypting File System. 

6. Now right-click on the certificate and choose All Tasks and then Export. Make sure to choose “Yes, export the private key” and then click Next.

7. Now type in a password and choose a file name for the export. You will get a warning message at the end, but simply allow access.

To import this same certificate on another computer so that you can view encrypted files, follow all the steps up to 4, then right-click in the right-hand panel and choose All Tasks – Import. Select the exported certificate and follow the wizard.

You will now be able to decrypt the encrypted files on the PC. Again, it is essential that you backup your keys before you reformat your computer or before something bad happens to it! If you are encrypting files and don’t have your encryption keys backed, you are asking to lose that data! Enjoy!