Related is the Gitcoin mining challenge from Stripe's Capture The Flag 3. Here's a writeup: https://github.com/ctfs/write-ups-2014/tree/master/stripe-ctf3/leve

Related is the Gitcoin mining challenge from Stripe's Capture The Flag 3. Here's a writeup: https://github.com/ctfs/write-ups-2014/tree/master/stripe-ctf3/level1 https://github.com/ctfs/write-ups-2014/tree/master/stripe-ct... A Gitcoin miner updates the ledger (a text file in the repo), and "mines" the next-smaller hash. It doesn't have consensus, but it does give a neat programming challenge.