Building the blockchain (Slides 8–9). Present the information that is to be stored in the first block (slide 8) and have participants enter this information in the first block (row) of the student handout (Student Handout.pdf). Be sure to point out the other columns in the block: Nouce, a, b, c, and the value of the last two digits of the previous hash. Emphasize that an origin block is used to begin the ledger when a blockchain is created. For our grade blockchain, the origin block has a hash of 212. As such, the last two digits (12) are entered into the appropriate field in block 1. Why? For right now, the students have to take your word; let them know that you will revisit this information later.

Mining and Hashes (Slides 10–12). It is now time to introduce the concept of hashing (slide 10) and give them the formula for the grade hash (slide 11). Walk them through looking up the values of a, b, and c in the look-up table (80, 65, 70 for the first block). It is essential to explain that the nonce is a variable for which they will solve. It will be 1, 2, or 3. The determining factor is which value for a Nonce will create a hash that is equally divisible by three. Doing math in public is hard! And some students will get flustered, So you might want to remind students what “is equally divisible by three” means (nothing after the decimal point).

Let them know that hashes often have to meet specific criteria. In Bitcoin, it might be that the first 16 bits are all 0s. We are making it simple. Also, let them know that blockchains would have a much more complicated hash. And that hashes are considered one-way functions.

Time to mine (still slide 12). The students will need to calculate the hash and respond when they have figured out the nonce (1, 2, or 3) either verbally (face-to-face) or through the chat on zoom. They should just share the nonce.

Once a student has announced what they think the correct nonce is, remind the class that there is no central authority to verify if that answer is correct. Instead, the blockchain will have to reach a consensus, and our criteria for consensus is that 51% of the nodes (students) agree. Ask everyone to stop their current work and see if they can verify the announced answer. Take votes via a show of hands (face to face), or chat.

It is essential not to make fun of someone who has the wrong answer for the nonce (1 for the first two blocks, 3 for the blocks three and four, 2 for blocks five and six). If a wrong answer is announced, I will talk through the calculation again, saying something like, “OK so what Joe is saying is if he takes 3+80+65+70 and then subtracts 12 he gets a number that is equally divisible by three, meaning that there’s nothing after the decimal point.” That usually is enough to get the students on the right track and the student with the wrong answer will change their vote.

I try to keep the conversation light by making some jokes about how math is not an exact science and that doing math in public is hard!

Reward the Winning Miner! Once the blockchain has reached a consensus, you want to reward the student who came up with the correct answer first. For face-to-face classes, I often give out little trinkets, notepads, etc. If you are in a zoom class, you may have to “give” them a funny image in the chat or bow down to them or some other student mention. This moment is an excellent time to talk about mining Bitcoin!

This is how Mag. Marie Nitzlader, Academic Lecturer at the University of Applied Sciences — Austria has modified the reward system! Very cool!

What I included in the game was an award in the form of virtual “FHWN coins” (FHWN is the German acronym for our university), which I decided represent our university-specific digital coins. The reward was halved after every second block was mined. I started with awarding 50 FHWN coins to the first two winners, then 25 to the next two successful miners, then only 12.5 coins.

At the end of the game, I asked them, whether they think that these coins were worth anything? Well, I had received some goodies from Corporate Marketing, like USB sticks, pens, post-its, a bag and similar low-value merchandising articles, and the student with the highest amount of coins was allowed to select a gift first. Then came the student with the second-highest amount of coins and so on. In the end, I had small give-aways for ALL students attending the class!

Review (slide 13). Some students will still be lost, so review the solution with the class. Note that we will be taking the last two digits of the block 1 hash (204) and putting it into the block 2 calculation (in the value of the last two digits of the previous hash field).

Build out the blockchain! (slides 14–23). Repeat the process for the remaining blocks (you don’t need to do all 6, but it gets much faster after the first couple of blocks. After a couple of blocks, you can start to have discussions about what is happening.