Uncovering StarkNet: Understanding Cairo

Introduction to StarkNet and Cairo

With StarkNet's mainnet launch in late 2021 and ongoing plans to further decentralize its infrastructure, StarkNet has positioned itself as a prominent leader within the blockchain development ecosystem and ZK (zero-knowledge) Rollup technology landscape. The platform aims to deliver significantly increased transaction speeds and exponentially reduced costs within a secure Ethereum-compatible environment, making StarkNet one of the most notable Layer 2 (L2) scaling solutions in the current market.

However, there is an important consideration for developers interested in building on this chain. StarkNet primarily utilizes Cairo as its main programming language, which differs from other ZK-Rollup solutions like zkSync 2.0. Unlike zkSync, which allows developers to recompile their smart contracts or Layer 1 applications written in programming languages such as Vyper and Solidity into the Layer 2 execution environment without modifying the base code, StarkNet requires developers to work directly with Cairo.

Despite this learning curve, Cairo has demonstrated impressive adoption and utility. StarkNet reports that Cairo ranks fourth in terms of TVL (total value locked) among smart contract languages. Applications built on Cairo have reportedly facilitated more than 300 million transactions, created 90 million non-fungible tokens (NFTs), and enabled trades valued at $790 million on the Ethereum network. These metrics clearly demonstrate that building on Cairo brings unique benefits and opportunities, which we will explore throughout this article.

What is Cairo?

Cairo is a high-level programming language specifically designed to be accessible and user-friendly for developers who are already familiar with mainstream programming languages such as Python and JavaScript. The language was purpose-built for use with the StarkNet platform, incorporating specialized features that enable developers to leverage StarkNet's unique capabilities.

These capabilities include exceptional scalability that far exceeds traditional Layer 1 solutions, as well as the ability to perform complex off-chain computations while maintaining cryptographic security guarantees. Cairo's design philosophy centers on making zero-knowledge proof generation accessible to a broader developer community, without requiring deep expertise in cryptographic mathematics. This approach allows developers to focus on application logic while the underlying STARK proof system handles the complex cryptographic operations that ensure computational integrity and security.

Von Neumann Architecture

As the first universal Von Neumann STARK architecture implemented for any blockchain on the Ethereum mainnet, Cairo represents a significant technical achievement and is often described as an MVL (minimum viable language) for producing STARK systems. The Von Neumann architectural approach provides Cairo with a high level of flexibility, as memory is shared between instructions and data. This shared memory model means that the allocation assigned to each component can dynamically fluctuate depending on the specific computational task being performed.

This architectural choice stands in contrast to the Harvard architecture, which is Cairo's structural counterpart. Harvard architecture is characterized by having separate memory spaces for data and instructions, which can result in comparatively limited flexibility. In Harvard architecture, there is only a fixed amount of memory that can be used for data and a predetermined amount for instructions, which cannot be reallocated based on computational needs.

The Von Neumann approach in Cairo allows for more efficient memory utilization, particularly important when generating STARK proofs where computational requirements can vary significantly depending on the complexity of the operations being verified. This flexibility enables Cairo to optimize resource allocation dynamically, leading to more efficient proof generation and verification processes.

Goldilocks Principle

Cairo maintains what is known as the "Goldilocks principle" in achieving an optimal balance between code expressibility and STARK prover efficiency. This principle is named after the fairy tale character who sought things that were "just right" – neither too much nor too little.

On one hand, Cairo is "not-too-hot" in that it contains a minimal register list consisting only of the Program Counter (PC), allocation pointer, and frame pointer. It employs a carefully curated minimal instruction set that is capable of performing low-level operations with high efficiency. With this small instruction set, the computational cost of saving, executing, and reading program instructions is significantly reduced, as less memory space is required to store the instruction code. This minimalism directly translates to faster proof generation times and lower computational overhead.

On the other hand, Cairo is also "not-too-cold" as it provides sufficient high-level features to enable practical application development. The language supports essential programming constructs such as functions, recursions, random memory access, and more sophisticated control flow patterns. This balance ensures that while Cairo remains efficient at the proof generation level, it doesn't sacrifice the expressiveness needed for developers to build complex decentralized applications.

Furthermore, Cairo is considered production-ready, meaning that beyond being merely a language specification, there exists a comprehensive and mature tool chain supporting Cairo development. This ecosystem includes a compiler for translating Cairo code into executable bytecode, a virtual machine for execution, a tracer for debugging, IDE extensions for popular development environments, and extensive application code examples. As the primary programming language for StarkNet, any decentralized applications (DApps) that wish to scale using StarkNet's infrastructure must be written in Cairo, making this robust tooling ecosystem essential for developer adoption and productivity.

Computational Integrity

One of the primary distinguishing features and selling points of Cairo as a programming language is its approach to Computational Integrity (CI). Computational integrity refers to the guarantee that a computation was performed correctly, which can be achieved through various mechanisms.

Traditional systems often achieve computational integrity through reputation and delegated accountability, as seen in the case of large financial institutions and banks where trust is placed in established entities. Another approach involves fraud proofs, such as those used in Optimistic Rollups, where "challenge periods" are made available for the public to dispute suspicious or potentially malicious transactions. During these challenge periods, validators can submit proof that a transaction was executed incorrectly, triggering a dispute resolution process.

Cairo, however, takes a fundamentally different approach by aiming to generate computational integrity statements through cryptographic proofs, specifically STARK (Scalable Transparent ARgument of Knowledge) proofs. In this system, a cryptographic proof is generated by a prover, which creates a mathematical attestation that consolidates and verifies the correctness of multiple transactions or computations. This proof is then transmitted to a verifier, which can efficiently check the proof's validity to achieve computational integrity.

The advantage of this cryptographic approach is that it provides mathematical certainty rather than relying on economic incentives or trust assumptions. The verifier can be confident that the computation was performed correctly without needing to re-execute the entire computation themselves. This property is fundamental to how StarkNet achieves scalability while maintaining security guarantees equivalent to Ethereum's base layer.

Cairo 1.0

In an important announcement made in early 2023, StarkWare Co-Founder Eli Ben-Sasson explained the upcoming re-genesis of Cairo on StarkNet, designated as Cairo 1.0. This significant upgrade represents a fundamental reimagining of the Cairo language and is designed to make Cairo emulate the popular systems programming language Rust. The primary motivation behind this redesign is to enable developers with general coding experience and familiarity with modern programming paradigms to begin building decentralized applications on StarkNet's Ethereum Layer 2 network more easily.

The Cairo 1.0 upgrade introduces numerous enhancements to the language's design and functionality. These improvements include refined syntax and language constructs that align more closely with contemporary programming language design, a comprehensive and robust type system that helps catch errors at compile time, user-friendly libraries that provide common functionality out of the box, optimized code generation for better performance, and the requirement to explicitly specify data types for strong typing, which improves code safety and maintainability.

A particularly noteworthy aspect of Cairo's revamp is the introduction of Sierra, which stands for Safe Intermediate Representation. Sierra functions as an intermediate representation layer that sits between Cairo 1.0 source code and Cairo bytecode. This additional layer serves several important purposes, including enabling safer upgrades, preventing certain classes of vulnerabilities, and providing better optimization opportunities during the compilation process.

With this comprehensive upgrade, the StarkNet team expects that Cairo will be more readily adopted by the mainstream developer community, thereby incentivizing more builders to bring their innovative projects onto the StarkNet platform. The reduced learning curve and improved developer experience are anticipated to accelerate ecosystem growth and application diversity.

Developers can now begin writing, compiling, and testing programs using Cairo 1.0 through the available development tools and documentation. It is important to note that Cairo 1.0 is continuously being improved and updated with new features and optimizations as the language matures. Developers interested in staying current with the latest developments can find the most recent updates, documentation, and community contributions on the official Cairo repository, which serves as the central hub for Cairo language development and community engagement.

FAQ

What is StarkNet? How does it differ from other Ethereum Layer 2 solutions?

StarkNet is an Ethereum Layer 2 scaling solution using ZK-Rollups technology. Unlike other Layer 2 solutions, StarkNet emphasizes zero-knowledge proofs for superior privacy and computational efficiency while maintaining Ethereum compatibility.

What are the characteristics of Cairo programming language? How can beginners start learning Cairo?

Cairo is Starknet's efficient low-level language with concise syntax. Beginners should start with official documentation and video tutorials to understand its core concepts and development workflow effectively.

How to develop and deploy smart contracts on StarkNet?

Write smart contracts using Cairo programming language, compile the code, then deploy using StarkNet's CLI or SDK tools for seamless contract deployment on the network.

What are the advantages of StarkNet using zero-knowledge proof technology?

StarkNet leverages zero-knowledge proofs to enhance scalability and transaction throughput while maintaining security and privacy. It enables efficient off-chain computation with on-chain verification, reducing costs and enabling faster processing without compromising decentralization.

How much improvement does StarkNet's transaction cost and speed have compared to Ethereum mainnet?

StarkNet significantly reduces transaction costs by approximately 95% compared to Ethereum mainnet, while substantially increasing transaction speed and throughput capacity for processing more transactions efficiently.

What are the main differences between Cairo and Solidity?

Cairo is designed for StarkNet with superior scalability through validity proofs, supporting in-memory hash maps unlike Solidity. Cairo offers better performance for complex computations and different syntax paradigms optimized for zero-knowledge proof verification compared to Solidity's Ethereum-focused design.

How to set up a StarkNet development environment locally?

Install Python and Rust, clone the Protostar repository, configure your environment variables, and run the setup scripts to initialize a local StarkNet node for development.

What are StarkNet's ecosystem projects? What applications are currently running?

StarkNet ecosystem has 105 projects in development, including DeFi, tools, GameFi, and NFT. Currently, several DeFi and NFT applications are operational on the network.