Keyboard shortcuts

Press ← or → to navigate between chapters

Press S or / to search in the book

Press ? to show this help

Press Esc to hide this help

Oddities and FAQs

Common questions and head scratchers.

Chain MMR

The chain MMR always lags behind the blockchain by one block because otherwise there would be a cyclic dependency between the chain MMR and the block hash:

  • chain MMR contains each block's hash as a leaf
  • block hash calculation includes the chain MMR's root

To work-around this the inclusion of a block hash in the chain MMR is delayed by one block. Or put differently, block N is responsible for inserting block N-1 into the chain MMR. This does not break blockchain linkage because the block header (and therefore hash) still includes the previous block's hash.