From blockchain to BlockDAG

Once each block also hashes the previous block’s hash, the blocks form a chain, and the chain is tamper-evident. Editing an old block breaks every block after it at once.

Change the data in block 2, then re-mine it. Blocks 3, 4 and 5 stay broken until you re-mine each of them in turn. That is the cost of rewriting history: not the one block you wanted to change, but all the work built on top of it.

The room for exactly one

This structure has a position for one block at each height. Two miners who find a block at the same moment produce a fork, and the rule that resolves the fork necessarily throws one side away.

Bitcoin manages this by making collisions rare — ten minutes per block. That is a real solution, and it costs you the block rate. Every attempt to speed up a single-chain protocol runs into the same wall: faster blocks mean more forks, more forks mean more discarded work, and discarded honest work is both wasted capacity and a security problem, because it is work not defending the chain.

Referencing more than one parent

Kaspa lets a block name several parents. Two blocks mined at the same instant are both kept, and a later block merges them by referencing both.

Add block on tips Add block on selection Undo Reset example

Click blocks to select parents, then add a block on that selection. Blocks with no children yet are tips.

Nothing is discarded, so the block rate is no longer constrained by fork rate. What it costs is the thing a chain got for free — a single agreed order — which is what GHOSTDAG exists to restore.