CryptoHack is a set a cryptography-based CTF challenges that are very well-constructed for learning. This is the story of the platform, and the ethos of the environment.
The creators (two of three are on the podcast episode) were novices are cryptography. In order to learn, they made challenges for the website, iteratively learning the material. They found that because they were in the middle of learning, they cared about the learning process more than the difficultly of the challenges.
On the website, there are courses to go alongside the challenges in order to make it easier. The challenges have hints in the title, links to papers/resources, and many other helpful aspects, depending on what's necessary for the challenge. Sometimes, the exploit is the goal, while other times the discovery of some property is.
Creation of challenges is really an art, while many CTF challenge creators want to make it as difficult as possible. It's easy to make something difficult; it's hard to make it intuitive. I found that the podcast has the same ethos as me for the Spokane Cyber Cup. They also used the development of the platform to learn, which was also the same as me.
Overall, a great podcast on community building, and how to make an environment as learnful as possible.