The consensus mechanism in Ethereum is based on the Greedy Heaviest Observed Subtree (GHOST) protocol proposed initially by Zohar and Sompolinsky in December 2013.
Readers interested in it can explore the detailed original paper at http://eprint.iacr.org/2013/881.pdf.
The Rules That Keep Blockchain Networks Agreed and Secure (Part 2)
Ethereum uses a simpler version of this protocol, where the chain that has most computational effort spent on it to build it is identified as the definite version.
Another way of looking at it is to find the longest chain, as the longest chain must have been built by consuming adequate mining effort.
GHOST protocol was first introduced as a mechanism to alleviate the issues arising out of fast block generation times that led to stale or orphan blocks.
In GHOST, stale blocks are added in calculations to figure out the longest and heaviest chain of blocks.
In case of Bitcoin, shown on the left-hand side in the diagram, the longest chain rule is applied which means that the active chain (true chain) is the one that has the most amount of PoW done.
Why This Matters for Blockchain Technology
In case of Ethereum, the concept is similar from the longest chain point of view but it also includes ommers (also called uncles), the orphan blocks which means that it rewards those blocks too that were competing with other blocks during mining to be selected and performed significant PoW or were mined exactly at the same time as others but did not make it to the main chain.
This makes the chain heaviest instead of longest because it also contains the orphaned blocks.
In Ethereum the algorithm used for this purpose is called Ethash which is described in the next subsection.
Key Points to Remember
- The consensus mechanism The consensus mechanism in Ethereum is based on the Greedy Heaviest Observed Subtree (GHOST) protocol proposed initially by Zohar and Sompolinsky in December 2013.
- Readers interested in it can explore the detailed original paper at http://eprint.iacr.org/2013/881.pdf.
- Ethereum uses a simpler version of this protocol, where the chain that has most computational effort spent on it to build it is identified as the definite version.
- Another way of looking at it is to find the longest chain, as the longest chain must have been built by consuming adequate mining effort.
Conclusion
The consensus mechanism represents one of the many innovative layers that make blockchain technology so powerful and transformative. As distributed systems continue to evolve, a solid understanding of these core concepts becomes increasingly valuable — not just for developers, but for anyone building, investing in, or working alongside blockchain-powered systems.
Whether you are just starting your blockchain journey or deepening existing expertise, mastering these fundamentals gives you the tools to think clearly about decentralized systems and make smarter decisions in this rapidly evolving space.