Coding on the blockchain

At the time of writing, the two most popular cryptocurrencies are Bitcoin and Ethereum.

Note

If you ask someone who knows a lot about cryptocurrencies a simple question, you may get the following answer: Bitcoin is just for sending money, but you can create a program on Ethereum. The program can be tokens, auctions, or escrow, among many other things. But that is a half-truth.

You can also create a program via Bitcoin. Usually, people call this program a script. It is necessary to provide a script in a Bitcoin transaction. A transaction in Bitcoin can be mundane, so if I want to send you 1 BTC (a unit of currency in Bitcoin) and your Bitcoin address is Z, I need to upload a script like this into the Bitcoin blockchain:

What's your public key? If the public key is hashed, does it equal Z? If
yes, could you provide your private key to prove that you own this public
key?

But it could be a little bit fancier. Let’s say you require at least...