Ouroboros Peras: accelerating transaction settlement on Cardano

Currently in development, Ouroboros Peras (henceforth Peras) is an advanced upgrade to the Ouroboros Praos consensus protocol that aims to accelerate transaction settlement while maintaining security and resilience on the Cardano blockchain. By introducing a new voting mechanism, Peras will ensure that transaction settling happens significantly faster, reducing the waiting period for users and limiting the risk of rollbacks.

Why do we need faster settlement?

In many blockchain systems, users must wait for multiple blocks to be added before their transactions are considered final. This process can take a long time, which is not ideal for everyday transactions or decentralized applications (DApps) that rely on quick confirmations. Peras addresses this by:

• Improving user experience. Shorter settlement times make Cardano more responsive and efficient for time-sensitive DApps.
• Enhancing security. Once a block is boosted (certified), the likelihood of chain rollbacks involving that block significantly decreases.
• Supporting bridges and partner chains. Quicker settlement streamlines transfers between Cardano’s main chain and partner chains, improving interoperability.
• Reducing confirmation requirements on exchanges. Quicker block settlement may allow centralized exchange (CEX) users to access their funds sooner.
• Enabling new use cases. Faster settlement creates opportunities for both decentralized and centralized services that benefit from rapid transaction settlement.

How does Peras work?

Peras introduces a new voting process that enables stake pool operators (SPOs) to certify blocks at designated intervals. Certified blocks carry additional weight, increasing their likelihood of being included in the heaviest chain. This method significantly accelerates transaction settlement while maintaining the security and decentralization of the blockchain. Here’s a simplified explanation of how it works:

1. Voting committee. A randomly selected group of SPOs participates in scheduled voting rounds.
2. Voting process. Each committee member votes on blocks at a certain depth from the tip of the chain. These votes are weighted by the stake each SPO controls.
3. Certified blocks. Blocks that collect enough votes reach certified status.
4. Weight boost. Certified blocks receive an added weight, influencing which blocks the network prefers.
5. Heaviest chain rule. Instead of using the longest chain rule, Peras relies on chain weight. Certified blocks have a larger impact on chain selection.
6. Faster settlement. By applying extra weight to blocks, the network reaches block settlement quicker, reducing the waiting time for irreversible transactions.

Please note that a more extended Peras design (still under consideration) can incorporate a BFT-like pre-vote step, ensuring committees converge on a single block to boost. If no block reaches certification, a ‘cooldown’ is triggered before reattempting. However, the core block production process (lottery-based) remains the same as in Praos.

Benefits of Peras

Peras focuses on rapid settlement while preserving the security and decentralization that the Ouroboros protocol series is known for.

Note that in practice, Peras is seen as the next evolutionary step for Praos rather than a direct alternative to the older protocols. Its use cases are most aligned with rapid settlement, while other protocols solve orthogonal problems (eg, privacy, time synchronization, or throughput).

For regular users

• Faster transaction confirmation. Peras reduces settlement times, delivering a more responsive experience for DApps.
• Reduced rollback risk. Faster settlement lowers the chance of chain reorganizations that can invalidate recent blocks.
• Improved user experience. Speedier settlement elevates Cardano’s appeal for day-to-day DApps and services.
• Enabling new smart contract use cases. While Peras does not influence smart contract execution, quicker settlement can open doors to time-sensitive smart contract applications.

For stake pool operators

• Increased influence and participation. SPOs actively vote in each round, reinforcing the network’s security while potentially improving reward distribution accuracy.
• Minimal operational costs. Only modest bandwidth increases are required for the new voting mechanism.
• Enhanced network stability. Peras’ self-healing features help the network recover from disruptions quickly.

By introducing a stakeholder-driven voting mechanism, Peras streamlines transaction settlements on Cardano while maintaining decentralization. This evolution in Cardano’s consensus design provides users with faster, more secure transactions, and empowers SPOs to help sustain the blockchain’s resilience and integrity.

Peras is currently in development. For more information and the latest progress, here are some useful links:

• Ouroboros Peras – faster settlement CIP
• Formal specification
• Peras research and development website
• Interactive simulator
• Probability calculator
• GitHub repository

• Ouroboros Peras: the next step in the journey of Cardano’s protocol video.