In proof-of-work blockchains, ommer blocks were created concurrently with another block but were not added to the main ledger. These elusive blocks, known as ommer blocks in Ethereum, are often discarded in favor of another accepted block. In the Ethereum blockchain, an ommer block could also be referenced as an uncle or orphan block, which describes familial relationships to explain block positions within the blockchain.
With Ethereum’s shift to the proof-of-stake mechanism in 2022, ommer blocks ceased to exist. However, blockchains utilizing proof-of-work still generate these ancillary blocks.
Key Takeaways
- Ommer blocks in Ethereum were produced when two blocks were validated at nearly the same time, but only one could be added to the blockchain ledger.
- Similar to Bitcoin’s orphan blocks, ommers had unique integrations in the Ethereum system.
- Ethereum rewarded the creation of ommer blocks via transaction fees for the validator’s work.
- After the DAO hack in 2016, Ethereum Classic forked off and continues to generate uncle blocks.
Understanding Ommer Blocks
In a public blockchain such as Ethereum or Bitcoin, it’s crucial to have a consensus method to ensure data integrity and verification. Therefore, the data structure known as a Merkle tree is utilized to establish ancestral relationships among blocks, fostering an unchangeable and verified blockchain ledger.
A Merkle tree embeds ancestral data within new blocks. It’s like the passing of DNA; information from a former block is carried over into the subsequent one, forming a family-tree-esque graphical representation with parent, child, and sibling blocks.
A Family Tree Example
Visualize an inaugural block, Block A. The ensuing block derived from Block A is its child and includes data from Block A along with additional new data, termed Block B a. This child inherits its parent’s information, creating a sequence of linkages forming the blockchain.
Envision two blocks validated simultaneously from B a; these are the sibling blocks, C ab and C ab2, derived from the same parent, Block B. The network selects Block C ab to be added officially to the blockchain. Conversely, Block C ab2 emerges as an ommer block—recognized but not added or validated.
Special Considerations
Such orphaned blocks were unintended mining process outcomes. However, Ethereum rewarded miners of ommer blocks for several strategic reasons:
- Encouraging the emergence of more ommer blocks to expedite short block times and enhance network speed.
- Reducing reward centralization toward massive mining pools and advancing decentralization, which allowed individual miners better chances at rewards.
- Strengthening network security by engaging miners further with ommer blocks.
Under Ethereum’s previous consensus mechanism, Casper the Friendly GHOST (Greedy Heaviest Observed SubTree), ommer blocks were deliberately integrated. Validators chose validated block inclusions during blockchain forks.
Following Ethereum’s shift from proof-of-work to proof-of-stake in 2022, ommer blocks became obsolete due to the altered block production protocol. Nonetheless, Ethereum Classic, a product of the 2016 DAO hack fork, persists in producing ommer (or uncle) blocks.
Other Insights
What Was an Ommer (Uncle) Block?
Known initially as uncle blocks, developers opted for the gender-neutral term ‘ommer.’ Despite the Ethereum community adopting ommer, these blocks are redundant under proof-of-stake.
What Is Ethereum’s Ommer (Uncle) Rate?
Previously called the uncle rate, the ommer rate was the frequency at which such blocks emerged, reflecting fluctuating transactional volume dynamics. This rate is irrelevant on the primary Ethereum blockchain post-transition.
What Was Ethereum’s Ommer (Uncle) Reward?
Earlier, the proof-of-work method granted rewards comprising a minor fraction of the block reward, supplemented by transaction fees, to the creators of ommer blocks. Following the transition to proof-of-stake in 2022, ommer blocks are no longer produced.
The Bottom Line
Ommer blocks represented extraneous yet indispensable elements created during Ethereum’s proof-of-work mining era. While not integral to the main ledger, these blocks were critical in Ethereum’s network infrastructure by providing additional layers of processing. “The Merge” in 2022 stood as a landmark transition, obviating the need for mining and, subsequently, the creation of ommer blocks.
Related Terms: blockchain, proof-of-work, proof-of-stake, mining, uncle blocks, Ethereum, cryptocurrency
References
- EthereumClassic.org. “Ethereum Classic Course: 8. Ethereum Classic’s Monetary Policy”.
- Ethereum.org. “Block Proposal”.
- Ethereum.org. “Proof-of-Work”.
