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Sub Blocks#

As of August 2023, lighter clients have seen considerable advancements with versions 5.0.12 and 5.0.13 of the reference client offering support for bootstrapping with UTXO set snapshots and NiPoPoWs. While Layer 0 (L0) optimizations continue to be a hot topic, there is an increasing demand for faster transaction confirmations.

subblocks are block candidates in the Ergo blockchain that have a lower difficulty threshold compared to standard blocks. For end-users, the introduction of subblocks aims to significantly speed up transaction confirmations to around 20 seconds and better utilize network bandwidth, ultimately providing a more efficient and responsive user experience. This document delves into the technical details, advantages, and the strategic plan for implementing subblocks using sidechains in Ergo.

The Scalability Dilemma#

While there are many proposals claiming to improve scalability, such as switching to Proof-of-Stake or DAG structures, the real issue often boils down to two key areas:

  1. Propagation Efficiency: How well transactions and blocks propagate through the peer-to-peer network.
  2. Network Load: Optimizing the network so that it remains decentralized and efficient.

Proof-of-Work, while not requiring additional messages for block creation, still needs improvement in how blocks and transactions propagate through the network.

Why Not Microblocks or Bitcoin-NG?#

Bitcoin-NG was initially considered in Ergo's 2017 roadmap but later abandoned due to competing proposals. The principle behind Bitcoin-NG was to use microblocks to follow an empty PoW block, which serves merely as a leader election signal. Although microblocks can improve network utilization, alternative solutions like compact blocks offer similar results. Therefore, Ergo is considering the use of "subblocks" as an alternative.

What are Sub blocks?#

subblocks are essentially block candidates with lower difficulty than a regular block. For instance, if a subblock has 1/128th of a regular block's difficulty, we could expect one subblock to be generated per second on average.


  1. Optimal Network Utilization: subblocks are sent around the network along with new transaction IDs, utilizing the network bandwidth optimally.
  2. Faster Confirmation: A transaction could be considered Subly confirmed with fewer confirmations from the majority hashrate, in practical terms, under about 20 seconds.
  3. Incentivization: subblocks can commit to sidechains, making fast sidechains possible and providing miners with additional rewards.


Sidechains allow for segregated, dedicated chains where specific tasks or applications can be run. This offloads the main Ergo chain, providing another avenue for scalability. subblocks can commit to these sidechains, adding another layer of efficiency and speed to the Ergo ecosystem.

Implementation Plan#

  • Use subblocks instead of microblocks for optimal network utilization and faster confirmations.
  • Distribute subblocks in a cut-through way similar to other efficient block propagation techniques.
  • Incentivize the reporting of subblocks by linking them to sidechain commitments.


subblocks and sidechains present an efficient approach to address some of the fundamental scalability issues in proof-of-work blockchains like Ergo. By focusing on these, Ergo aims to improve both the network efficiency and transaction confirmation speed without compromising decentralisation.