StarkNet's Privacy Features vs Aztec's zkRollup: A Technical Analysis

StarkNet excels at providing selective privacy and confidentiality for specific on-chain actions within its general-purpose zkRollup. Its core strength is the Cairo programming language and tools like starkware-libs/apex, which allow developers to build applications where sensitive logic is hidden while leveraging the public chain's liquidity and composability. For example, a DeFi protocol can use a private voting mechanism on StarkNet while its token remains publicly tradable, avoiding the fragmentation of total value locked (TVL).

Aztec takes a fundamentally different approach by being a dedicated privacy-first zkRollup. Its architecture, based on the Plonk proof system and private state trees, ensures all transactions are encrypted by default. This results in a powerful trade-off: unparalleled privacy for applications like private voting or confidential DAO treasuries, but at the cost of being a separate, application-specific rollup that cannot natively interoperate with public smart contracts on Ethereum mainnet without a bridge.

The key trade-off: If your priority is selective privacy within a broader, composable DeFi ecosystem (e.g., hiding auction bids in a public NFT marketplace), choose StarkNet. If you prioritize absolute, default-on transaction privacy and are building a standalone application (e.g., a confidential payroll system), choose Aztec's specialized rollup.

Aztec's zkRollup excels at default, programmable privacy because it uses a UTXO-like model and private state trees to hide sender, receiver, and amount by default. For example, its Aztec Connect bridge processed over $100M in private DeFi volume, demonstrating a working model for private smart contract interactions. This architecture is ideal for applications like confidential voting, private payroll, or shielded DeFi, where privacy is the non-negotiable core feature.

StarkNet takes a different approach by being a public, high-performance L2 that enables privacy as an optional feature via cryptographic primitives like starkware-crypto and account abstraction. This results in a trade-off of flexibility for raw throughput, leveraging STARK proofs to achieve higher theoretical TPS (potentially thousands) and seamless composability with its public state. Its ecosystem, with protocols like zkLend and Nostra, benefits from this open environment for transparent, high-speed applications.

The key trade-off: If your priority is built-in, mandatory privacy for every transaction and you are building a novel privacy-first dApp, choose Aztec. If you prioritize maximum scalability, public composability, and the ability to optionally integrate privacy into a broader application (e.g., a game with private items or a DEX with hidden orders), choose StarkNet. Consider the state of mainnet maturity; StarkNet's public ecosystem is currently larger, while Aztec offers a more specialized, privacy-guaranteed environment.