As you probably know, Dropbox is the most convenient and the most popular cloud storage system among individual consumers, but it’s far from being too secure. On the other hand, Google Drive and Box.com are a bit more secure, the latter even being trusted by corporate entities, but I don’t trust them either, because where there’s a back door for the big brother, there’s one more possible crack in the system. Not that the big brother doesn’t care about consumer and individual account security, but I think that’s a little bit lower on their list of priorities, and just like in the real life, the thieves will go for the back door.
For that and other reasons to keep your files off the cloud I keep my files on local devices, properly backed up. However, if I ever had to upload anything confidential, the only way I would trust the cloud would be by taking care of the encryption myself. When I think of that, the only secure technology that comes to my mind is TrueCrypt. Being free and open source, TrueCrypt is almost perfect for that purpose, provided that you keep your encrypted depositories small enough so that they can sync and update over the internet. Then you can hold these files in your Dropbox and mount them as drives on your computer using Dropbox combined with TrueCrypt software. This is great for written documents, but encrypting and uploading multimedia files or movies can be pushing it, depending on your internet connection speed. If you have a high speed broadband connection this is not as limiting, but the slower your connection, the smaller the volumes (depository files) should be, to make synchronization faster.
The downside of this encryption is that it is too good (if there is such a thing), meaning that if you forget your password(s), you can kiss your files goodbye forever, or for at least a few decades until there’s much more powerful computing available to break the encryption.
Another downside of an encrypted TrueCrypt file is that it keeps its maximum size you select for it at creation regardless whether you have one small or many big files in it and requires being mounted as a volume (drive letter or an item showing for example under My Computer in Windows), but that’s the nature of the security – it doesn’t mix too well with convenience. For this reason EncFS could be another, more convenient but less secure solution than TrueCrypt. EncFS doesn’t occupy blank space and grows as files get added. However, individual files encrypted with EncFS are visible and so is their number, their modification date, permissions and size, while each TrueCrypt volume appears as one big unreadable chunk of data, regardless how many files it contains. One extra security feature of TrueCrypt is that it can be set up with another hidden volume inside its encrypted space with a different password, what can help users in countries with oppressive regimes protect themselves from being persecuted. Both solutions work well with Windows, Mac OS X and Linux.