Current consensus protocol of Ethereum LMD-GHOST is not secure even in a context of full participation - It's subject to **long-range attack** - when someone who used to control a lot of validators, but no longer does, can use their keys to create an alternate history that appears valid to new or offline nodes joining the network - The reason for this vulnerability is because there's no mechanism for finality. - This is why Casper FFG is used to finalize blocks and prevent changes in blockchain history before the finalized block GHOST Function explained: 1. Start at the genesis block 2. From the current block, look at its children blocks 3. Choose the child block with the heaviest subtree. Weight of subtree determined by votes (previously most computation done upon it) 4. Repeat steps 2-3 with the chosen child block as the current block until you reach a block that has no children. This block is the head of the chain. [[RLMD-GHOST]] represents middle ground between LMD-GHOST, an asynchrony resilient but not dynamically available protocol, and [[Goldfish]], a dynamically available but not asynchrony resilient protocol. It's resilient to bounded asynchrony *up to a vote expiry period*, and satisfies an appropriate notion of dynamic availability.