One of the most powerful security tools available to web developers is cryptography, essentially a process by which meaningful information is turned into random noise, unreadable except where specifically intended. A web developer working on an underpowered netbook in his basement now has access to cryptosystems that major governments could only have dreamed of a few decades ago. And ignorance of cryptography is not bliss. You may think your web app’s profile is too low to worry about hackers, but attacks are frequently automated, not targeted, and a compromise of the weakest system can often give access to better-protected systems when people re-use passwords across multiple sites. Learn the three broad categories of cryptosystems that commonly relate to web applications and begin strategizing how to make your site secure.