Expalin hash functions.
Now, this is hard. But here are some thoughts:
- Ignore non-cryptographic hash functions. While superficially similar, they have different use cases and would only cause confusion.
- Hash as a fingerprint, see Cinderella story by Dominic Tarr: http://dominictarr.com/post/154769946347/fairly-tale-cryptography-2-hashes
- One option would be to start with promises. It's an easy to understand use case. Naturally branches off the time traveller tale.
- Also, look at tallies.