Add a new transaction to the end of the chain saying that counterparty X has paid you $1B.  Publish this transaction.  Counterparty X, of course, publishes a version of the blockchain where you have paid them $1B dollars.  How do participants in a private blockchain determine which published version represents reality?<p>Or alternatively: Pay counterparty X $1B.  Then immediately turn around and pay counterparty Y <i>the same $1B</i>, before they&#x27;ve gotten an updated ledger from counterparty X.  When counterparty X and Y share their ledgers, who owns your $1B?<p>The point of mining in Bitcoin is to resolve conflicts like this.  By forcing whichever node digitally signs the latest block to perform a computationally-intensive problem, it represents that the latest block is the consensus of a majority of the network, as measured by computing power.  Any node is free to publish a fraudulent block, but then any other node can inspect the block, see that the SHA256 hash doesn&#x27;t match, and then reject it.  Or if they get lucky and happen to find the right SHA256 hash, they will get outpaced on the <i>next</i> block (the Bitcoin protocol specifies that clients should assume the longest chain is correct), and the rest of the network will ignore their fraudulent transaction.<p>What&#x27;s the alternative in private blockchains?  I&#x27;m genuinely curious; I have little invested in Bitcoin, but I did spend some time understanding how the protocol works and why it includes the features it does.