People often make the mistake of believing that they can control the privacy for content they post online. It’s easy to see why they fall into this trap. Facebook and YouTube both offer privacy controls. Facebook along with Twitter also provide private messaging. However, online privacy settings are only as good as the provider makes them:
Facebook disclosed a new privacy blunder on Thursday in a statement that said the site accidentally made the posts of 14 million users public even when they designated the posts to be shared with only a limited number of contacts.
The mixup was the result of a bug that automatically suggested posts be set to public, meaning the posts could be viewed by anyone, including people not logged on to Facebook. As a result, from May 18 to May 27, as many as 14 million users who intended posts to be available only to select individuals were, in fact, accessible to anyone on the Internet.
Oops.
Slip ups like this are more common than most people probably realize. Writing software is hard. Writing complex software used by billions of people is really hard. Then after the software is written, it must be administered. Administering complex software used by billions of people is also extremely difficult. Programmers and administrators are bound to make mistakes. When they do, the “confidential” content you posted online can quickly become publicly accessible.
Privacy is like anything else, if you want the job done well, you need to do it yourself. The reason services like Facebook can accidentally make your “private” content public is because they have complete access to your content. If you want to have some semblance of control over your privacy, your content must only be accessible to you. If you want that content to be available to others, you must post it in such a way where only you and them can access it.
This is the problem that public key cryptography attempts to solve. With public key cryptography each person has a private and public key. Anything encrypted with the public key can only be decrypted with the private key. Needless to say, as the names implies, you can post your public key to the Internet but must guard the security of your private key. When you want to make material available to somebody else, you encrypt it with their public key so hey can decrypted it with their private key. Likewise, when they want to make content available to you they must encrypt it with your public key so you can decrypt it with your private key. This setup gives you the best ability to enforce privacy controls because, assuming no party’s private key has been compromised, only specifically authorized parties have access to content. Granted, there are still a lot of ways for this setup to fall apart but a simple bad configuration isn’t going to suddenly make millions of people’s content publicly accessible.