A funny thought came to my mind. Can't stand but share it.
Git came out 3.5 years before bitcoin.
0) Git computes SHA of commit by hashing the whole contents of the commit including SHAs of parents.
1) Harden SHA computation with nonce concept, i.e. enforce that SHA ends with K zero bits (by varying a useless "nonce" parameter inside commit). As a result, you get a blockchain.
2) Store only one file with the list of money transactions in the repo.
3) Make it mandatory for users to sign their payments with their SSH private key. You got a cryptocurrency.
Should we call it GITCOIN?
A minor note: all requirements should be checked in the main commit validation code, so that every client checks every commit the same way and ignores invalid ones.
a. The only file is a list of transactions, and every commit only appends to this file.
b. Every ordinary transaction must be correctly signed by payer.
c. Allow one special transaction without payer per commit, with value computed using hard-coded formula --- this adds emission.
d. SHA format requirement from nonce. The number K is computed from current date: increment it every X days and you get finite supply.
If some people try to establish different rules, they will get incompatible history. It is called a hard fork. The impact of this fork depends on how much people start using it.
It looks like the shortest way to explain how bitcoin works internally to a seasoned programmer