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State Model


We are building Aztec as transparently as we can. The documents published here are living documents. The protocol, sandbox, language, and tools are all subject to change over time.

Please see here for details of known Aztec protocol and Aztec Sandbox limitations.

If you would like to help us build Aztec:

  • Contribute code on GitHub; or
  • Join in forum discussions.

Private State

Private state must be treated differently from public state and this must be expressed in the semantics of

Private state is encrypted and therefore is "owned" by a user or a set of users (via shared secrets) that are able to decrypt the state.

Private state is represented in an append-only database since updating a record would leak information about the transaction graph.

The act of "deleting" a private state variable can be represented by adding an associated nullifier to a nullifier set. The nullifier is generated such that, without knowing the decryption key of the owner, an observer cannot link a state record with a nullifier.

Modification of state variables can be emulated by nullifying the a state record and creating a new record to represent the variable. Private state has an intrinsic UTXO structure and this must be represented in the language semantics of manipulating private state.

Abstracting UTXO's from App's / Users

The goal of the smart contract library is to abstract the UTXO model away from an app user / developer, contract developers are the only actor who should have to think about UTXO's.

This is achieved with two main features:

  1. Users sign over transactions, not over specific UTXO's
  2. contracts support developer defined unconstrained getter functions to help dApp's make sense of UTXO's. e.g getBalance(). These functions can be called outside of a transaction context to read private state.

Coming soon

  • Public State
  • The lifecycle of a note
  • Custom notes
  • Injection of data by the kernel
  • Nonce & contract address
  • Custom nullifiers
  • Emission of custom note data to L1
  • Decrypting and storing encrypted note data

Further reading

Read more about how to leverage the Aztec state model in Aztec contracts here.