Public vs. Private State: Aleo’s Innovative Solution to Blockchain Data Storage

Blockchain technology promises transparency and security, but it’s also essential to give users control over their privacy. Since the concept of zero-knowledge proofs (ZKPs) emerged in 1985, cryptography has evolved to help realize this vision. Early adopters like Zcash and recent zkEVM Layer-2 chains have demonstrated that zero-knowledge cryptography can add privacy and improve scalability. However, the majority of these applications focus on one or the other — privacy or scalability.

Aleo, a layer-1 blockchain, goes beyond this limitation. Aleo not only integrates privacy and scalability by default but also gives developers the power to choose which data should be public or private. In this article, we’ll explore how Aleo’s state storage model works and why this dual approach is so promising for blockchain development.

Aleo State Storage: Privacy as the Default with Flexibility for Transparency

Aleo’s record model allows for secure, private data storage on-chain, providing a structure similar to the UTXO model used in Bitcoin, but enhanced with encryption for added privacy. Aleo takes this a step further by enabling developers to designate specific application states as public, leveraging a traditional account model (like Ethereum) for publicly viewable states. This flexibility opens up possibilities for creating applications that can balance privacy and transparency based on unique use cases.

Storing Private States with Records

In Aleo, records are core data structures that store user assets or application states, serialized in a secure format. Each record represents a specific state within a program — whether it’s a user’s balance or an encrypted document — ensuring that only the designated owner can modify it. By default, these records are stored as ciphertext on-chain, preserving user privacy.

Records are specifically tied to individual programs deployed on Aleo, giving users fine-grained control over which states they want to keep private, while ensuring secure storage.

Storing Public State with Mappings

For use cases that benefit from transparency, Aleo provides the option to use mappings — key-value pairs accessible to anyone querying the Aleo Network. This makes publicly stored data easily accessible, enabling applications that require open data structures without compromising user security on private data.

Switching Between Privacy States: Flexible for Real-World Scenarios

Aleo’s unique structure supports switching between private and public states as needed, allowing for dynamic changes within an application’s life cycle. Imagine a poker game where certain data points, like the shuffled deck, remain private initially. However, as the game progresses, the top three cards (the “flop”) are revealed to all players, transitioning from private to public.

This ability to convert between public and private states is a key feature that expands what developers can create on-chain, accommodating use cases like gaming, finance, and more that require selective data transparency.

Enhanced Control with View Keys

Aleo introduces a novel feature: the view key. Unlike the private key, which controls spending, the view key lets users decrypt their transaction history without having the ability to alter it. This ensures that while a user’s transaction details remain private to others, they can still audit and view their own activity whenever needed. This feature supports self-sovereignty in data access without compromising security.

Public vs. Private State: A Two-Pronged Approach for Developers

Choosing whether to make an application state public or private depends on the specific needs of the application. Rather than enforcing complete privacy or total transparency, Aleo offers a two-pronged approach that allows developers to configure the ideal privacy level for each part of their program.

Real-world applications often depend on a mix of private and public information. Take voting as an example: a voter may want their individual choice to remain confidential, but the overall tally should be accessible to all for verification purposes. Aleo’s dual model supports these diverse needs, making it easier to design applications that require trust without sacrificing user privacy.

Why Aleo’s Programmable Privacy Model Stands Out

As one of the few layer-1 blockchains prioritizing programmable privacy, Aleo provides developers with the unique ability to design applications with selective transparency. This capability enables a range of applications that are difficult to achieve on other blockchains, including secure voting systems, privacy-preserving gaming applications, and compliant financial systems.

Get started with building on Aleo by exploring the resources available on GitHub and the Aleo developer documentation. Aleo is bridging the gap between privacy and transparency, redefining what’s possible in blockchain development.