unencrypting files that somehow got encrypted

[mm]

A staff member has some files (he created in the past) which he can no
longer access. The files somehow became encrypted. He is the owner and
creator of the files. The files are located in his private users folder so
I dont think anyone else could have encrypted it.

As the domain administrator and recovery agent I have tried unencrypting
the file without success. I have exported his certificate and then
imported into my certificate store, but still no success in unencrypting.

Can someone help?

 

[Ndi]

As the domain administrator and recovery agent I have tried unencrypting

the file without success. I have exported his certificate and then
imported into my certificate store, but still no success in unencrypting.

If his key does not work, it's most likely because of a reinstall (or
fiddling with the certificates). If so, you need the backup from before
that.

If you do have it and it still doesn't work, it's because he most likely
encrypted the files with the 128bit update installed and the update is no
longer installed. This will cause the key not to work because of algorithm
differences. Install the 128bit upgrade on his system.

If you don't have the key with which the files were encrypted, the files
are lost.