 So if you think back to the 1970s, we got the first public block ciphers like the data encryption standard. In the 1980s, academics began to really develop open public key crypto and do interesting things with it. That was the development of zero knowledge and all sorts of powerful crypto primitives. But it wasn't until the 1990s that public open source software to do useful things with cryptography actually came out. And the most famous of those programs came out in 1991. It was called Pretty Good Privacy, or PGP. It was written by Phil Zimmerman. And there's a story behind that of what inspired Phil Zimmerman to write this software. And I'll come back to that in a moment. But what you should know about PGP, if you don't already know about PGP, is it was the first piece of PC software that lets you take advantage of public key crypto. The 1991 version was pretty awful, but it was crypto analyzed and improved and became something that was very powerful. There are other things that happened in the 1990s. There were DES challenges, so people started caring more about crypto. In 1994, something very important that's not end to an encryption related, something very important to happen, which is that the first version of the SSL protocol was released by Netscape Communications, which suddenly made encryption into something the industry required, as opposed to something that open source advocates cared about. And in 1996, new crypto libraries were put out and 1998 open SSL came out. And that's kind of the history of what was happening in the 1990s.