> ## Documentation Index
> Fetch the complete documentation index at: https://docs.starknet.io/llms.txt
> Use this file to discover all available pages before exploring further.

# System architecture

> Pool contract, proof verifier path, client-side proving, and compliance

The design has three pillars (paper §3):

1. **Privacy pool state contract**
2. **Proof verification path**
3. **Client-side proving + compliance data model**

## Pool and verifier

The privacy pool contract handles state transitions (note creation, nullifier publishing, deposits, withdrawals). Proof verification happens at the **sequencer level**, not in a separate smart contract—the Starknet sequencer verifies the ZK proof before executing the transaction. The mainnet pool contract is deployed at [`0x0403…812a`](https://voyager.online/contract/0x040337b1af3c663e86e333bab5a4b28da8d4652a15a69beee2b677776ffe812a) and its source is readable on Voyager.

## Client-side proving

A transaction requires a ZK proof. The proof shows that it was generated in a virtual Starknet execution environment (SNOS) anchored to a recent block. In the current phase, **designated operators generate proofs on behalf of users**. Proofs can also be created client-side using Stwo locally; they typically take ±30 seconds on a strong laptop.

## Compliance model

Each user registers a public viewing key and an auditor-encrypted private viewing key, enabling selective traceability under lawful requests.

Next: [Notes and nullifiers](/build/starknet-privacy/notes-and-nullifiers).