Celo Tech Talks Plumo Towards Scalable Interoperable Blockchains Using Ultra Light Validation System


The transcript is from part four of the Celo Tech Talks series, presented by Judy Piper, an engineer at Celo. The series aims to share Celo technology knowledge with the community, covering topics such as mobile applications, distributed systems, blockchain, cryptography, and infrastructure. The previous sessions are available on the Celo Foundation’s Crowdcast and YouTube channel.

Introduction to Plumo

Mike Straka, a crypto engineer partner, introduces Plumo, a new ultra-light class validation protocol developed by the SC Labs team. Plumo is a proof-based light client, designed to address the challenge of resource-constrained mobile devices accessing large blockchain data. Traditional blockchains like Bitcoin require downloading large amounts of data, making it difficult for normal users or smartphones with limited storage space. Plumo aims to provide an efficient solution for light clients by utilizing proof-of-stake mechanisms.

Light Clients and Proof-of-Stake

A light client is a way to interact with a blockchain without downloading the entire chain. In the context of proof-of-stake, Celo’s consensus mechanism, a light client allows users to get a sense of the blockchain’s state and participate in transactions without the need for extensive data storage. By implementing a simplified payment verification assumption, light clients can efficiently verify specific transactions without the overhead of downloading and processing the entire chain.

SNARKs and Efficiency

Plumo leverages SNARKs (Succinct Non-interactive Arguments of Knowledge) to achieve greater efficiency in light client validation. SNARKs enable the verification of a large amount of data using a small proof size. By running a setup algorithm that generates a common reference string, Plumo establishes shared randomness between the proving and verifying parties, resulting in more efficient validation.

Verifying Validators and Epoch Blocks

Plumo introduces the concept of verifying validators and epoch blocks. Validators are identified by their public keys, which are included in the epoch block headers. By verifying the BLS signatures of these public keys, light clients can confirm the legitimacy of the validators. Additionally, multi-signatures and bitmaps are used to ensure the required number of validators have signed a block. SNARK proofs can also be verified within Plumo, allowing for efficient verification of multiple epochs or selective checkpoints.

Efficiency and Future Considerations

Plumo offers significant efficiency improvements in verifying signatures and conducting arithmetic operations within finite fields. The use of specialized curves and algebraic operations optimizes the performance of cryptographic computations. Verification times are reduced, even on slower devices, making Plumo an attractive solution for resource-constrained environments. Furthermore, Plumo supports interoperability by enabling efficient verification through smart contracts.

Conclusion and Future Developments

In conclusion, Plumo represents a significant step towards scalable and interoperable blockchains using ultra-light validation systems. It leverages SNARKs and optimized cryptographic operations to provide efficient validation for light clients. The development team continues to explore further enhancements, such as variable proof lengths for different epoch durations, to improve efficiency and adapt to evolving blockchain requirements.