I empathize with you. I also was a math teacher. But I didn't have the luxury of having a group of students that could comprehend lofty ideas such as compound interest let alone addition and multiplication. I am not joking. I did get the class to all pass with a little (actually a lot) of after school tutoring. This is what I did, but it was very unstructured. By this I mean I had to read each student's hot points and create a math lesson based on these hot points.

For example, if a person was interested in sports I would put a math problem into a sports question. The other thing I had to take a few steps back. For example, to explain multiplication I explained adding things multiple times.

I your example you could explain blockchain by having them play a revised form of telegraph. Instead of having them whisper something to each other on down the line. Have them give each other a piece of paper with the same thing written on each piece. Then after everyone has a piece of paper, you can explain that this is how the blockchain works. Now multiple people (or computers / servers) have the exact same information.

As a teacher I'm sure you have the ability to come up with an example to get your point across. If some don't get it, I use to get the ones whom did try to get the point across. Sometimes students learn better from their peers and it makes the ones whom succeed in explaining it learn it better. Killing two birds with one stone.

Enough of my blabbing. I hope this might help. Have a nice day.