Probably due to the incessant scandal with the NSA and the notorious PRISM program at Google decided to save themselves from the encroachments of the state, distancing itself from the potential possibility of spying on users' files.
As they say in such cases, "from unnamed sources" CNET journalists learned that the Google Drive team is testing a new feature of their service - file encryption. It says that some of the files are already encrypted, so we can assume that encryption and decryption operations will be transparent to the file owner and will not require any effort from him - he will simply know that his content is “seemingly” unavailable the encroachments of special services like the NSA or the CIA. Last April, Teresa W., public relations manager of the Docs & Drive project, answered the direct question of the user whether the files were stored in Google Drive in an encrypted form in the sense that, although the company takes all measures to ensure User security - HTTPS and two-factor authentication - the downloaded files themselves can potentially be read in the usual way.
Although the technical perfection of the new Google initiative and, accordingly, the privacy of users, of course, raises questions, it is worth noting that there are already cloud services offering client-based file encryption - such as SpiderOak or Wuala. ')
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