You have reached the first checkpoint in the 'Journey to cryptography'-series. And now I want to talk about what's next, because I'm working on a new series. However, this one won't end here. If anything, we are kind of at the beginning still. So I'm going to do 3 different checkpoint videos. This one is on 'Advanced Lessons'. However, I also want to eventually talk about Tests and Challenges, and what we can do with more interactive explorations and computer science lessons as it applies to cryptography. But for now, let's talk about Advanced Lessons. When I say 'Advanced', I don't necessarily mean 'harder lessons', I mean 'more detailed'. Let me give you a conceptual idea for what I think this series could be and future series. I like to think of each series as the trunk of a tree, where I took you from prehistoric times to around the 20th century, which is here, with a few different threads. And these ideas kind of branch apart. Once you get to the 20th and 21st centuries, they start getting highly specific. And way down here on the leaves are current research questions, which over here might be problems related to prime number distribution and over here some very specific work being done on randomized algorithms or hash functions, and way up here we might have new public key protocols - because RSA was just the first - or we also have encryption standards such as DES and AES. We would have a whole new branch on quantum cryptography. So as you can see, there are so many different things that branch out of this series and I couldn't possibly do justice to them all. So I think of this video as living right here. At kind of a junction point. Now I can branch off with help of the community and possibly other video creators to fill out this tree gradually over time. Specifically with the help of the community. I am really excited about the Q&A community and the work being done to improve how people can help people on Khan Academy. So, for example, in terms of where one of these branches can go, I've noticed clusters of questions kind of leading into a common branch. For example, under 'the pseudo-random number generator', I have two questions here: one by Sonny and one by Drakain. Drakain's question is: "Why has he suggested that time in milliseconds... ...is a suitable random seed?... This is a huge no-no in security. ... The time it is on your machine... ...is the time it is on my machine,... ...give or take 100 milliseconds... (which can be brute-force attacked)" And again, this is a great question too because it speaks to the need that I didn't present a cryptographically secure pseudo-random generator. So the middle square's method is back here in early 20th century, but up until today, we are not using the middle square's method and that's a whole interesting branch. It is these sorts of questions which cluster together and really drive new content. I want to show you a really interesting example of how this has happened already. This is a question Samuel asked on the 'One time pad'-video he said: "wouldn't a computer be able to test all the possibilities very fast?" and Chuck Patrol basically asked the same question. I see this happening a lot. Similar questions all speak to the need of a new video. So I went and created a video on 'perfect secrecy' which really nails down how you can't beat randomness in the world of encryption. Out of this video, Dawn made a really great comment. What they did, was basically summarise my video in two sentences. So, this is what I want to try to do more of in filling out these branches: take questions, make new content, and have this feed-back loop and see what we can do. Now what I would really love, is for you to ask questions below this video which arise after watching the entire series. Not specific details about certain video's, - those can go with the videos - but new questions, which are opening new can of worms. And what I think will be fun to do, is: Your question will lead to answers, by both me and the rest of the community, so we'll have multiple answers. And what I can do is take this body of answers, and out of this draft up a rough script for more advanced videos on specific topics that sub-sets of the community care about So hopefully, out of the discussion below, over time we can grow a bunch of new videos! I want to be clear: this is an ongoing process. This will not happen tomorrow or next week. I hope it can happen months, even years from now. We can still be building out new videos after the series and these videos can be a collaborative effort between myself and the community and perhaps other video creators down the road. So, let me know what you think below, and let's get started!