Re: Nobody will be able to do this (Score 1)

Nah. Doable. The easiest solution is probably not available, though. Need to conduct a 51% attack. If it's pow, you'll need to throw hash power at it. If it's clique or that other protocol Parity uses (whose name escapes me), which is likely since most reasonable private networks are, then you're boned because you'll need a quorum to add nodes and if you have control of that you don't need the attack. 51% attack will let you approve the transactions you need to set the balances to the ransom, return the ransom funds to those wallets that paid, and then delete the contract, rendering the funds irretrievable and irrelevant. The keys could unlock and you're saved. This isn't realistic on a real public chain, unless you're the NSA with almost unlimited compute resources available. Now if it's a matter of hacking the contract, that's a different story, but start with tools like Mythril or Quantstamp and see what you find. This will be the only approach if it's a POA network instead of POW because if you had the quorum to add sealer nodes you already have the 51% attack right there.