[woah]

The private blockchains are generally using proof of stake protocols like Tendermint, or just classical byzantine fault tolerant protocols instead of proof of work. These protocols can be trusted if at least 2/3 of the participants can be trusted and there is no hashing involved at all.

They are generally replacing trusted third parties like clearinghouses. Instead of needing to trust (and pay for) a third party clearinghouse running a centralized db, these enterprises just need to trust that 1/3 of the participants in the consortium running the blockchain won't collude to attack the protocol. And even if there is an attack, there will be a big paper trail.

You may ask "why not just use a BFT database system with signed logs?" Well, this is what a blockchain basically is, wrapped in a package with a bunch of other stuff.