Why do I need to have BitLocker or a non-Microsoft drive encryption solution enabled before indexing encrypted files?
If you choose to add encrypted files to the index and you are not using a full volume encryption solution for the location of the index, encrypted data from your files—for example, text from a Microsoft Word document—will be added to the index. The index is obscured so that it is not easily readable if someone tries to open the index files, but it does not have strong data encryption. If someone were to gain access to your computer, they could extract your data from the index. Therefore, the location of the index should also be encrypted to help protect your indexed data.
