privacy-pools-core/docs/docs/protocol/deposit.md

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Deposit

The deposit operation is the entry point into the Privacy Pools protocol. It allows users to publicly deposit assets (ETH or ERC20 tokens) into a pool, creating a private commitment that can later be used for private withdrawals or public ragequit operations.

Protocol Flow

sequenceDiagram
    participant User
    participant SDK
    participant Entrypoint
    participant Pool


    Note over User: Generate random:<br/>nullifier, secret
    User->>SDK: Prepare deposit

    activate SDK
    SDK->>SDK: Compute precommitment<br/>hash(nullifier, secret)
    SDK-->>User: precommitment
    deactivate SDK

    alt ERC20 Deposit
        User->>Entrypoint: approve(amount)
        User->>Entrypoint: deposit(token, amount, precommitment)
    else ETH Deposit
        User->>Entrypoint: deposit{value: amount}(precommitment)
    end

    activate Entrypoint
    Entrypoint->>Entrypoint: Deduct fees
    Entrypoint->>Pool: deposit(msg.sender, value, precommitment)
    deactivate Entrypoint

    activate Pool
    Pool->>Pool: Generate label<br/>Insert commitment
    Pool-->>User: Emit Deposited(commitment, label)
    deactivate Pool

    Note over User: Store: nullifier, secret,<br/>label, value

Commitment Structure

The deposit process creates a commitment with the following structure:

graph TD
    A[Commitment Hash] --> B[Value]
    A --> C[Label]
    A --> D[Precommitment Hash]
    D --> E[Nullifier]
    D --> F[Secret]

Parameters

Parameter	Description
value	The deposit amount after fees
label	keccak256(scope, nonce) where scope is pool-specific and nonce is incremental
nullifier	Random value used to create unique commitments
secret	Random value that helps secure the commitment
precommitment	Hash(nullifier, secret)

Deposit Steps

1. Input Preparation

• User generates random nullifier and secret values
• User computes precommitment = hash(nullifier, secret)

1. Deposit Transaction

• User calls Entrypoint's deposit function with asset, amount, and precommitment
• For ETH: deposit(precommitment) with ETH value
• For ERC20: deposit(token, amount, precommitment) after approval

1. Fee Processing

• Entrypoint calculates and retains vetting fee (configurable per pool)
• Remaining amount is forwarded to pool

1. Commitment Generation

• Pool generates unique label using scope and incremental nonce
• Computes commitment hash using value, label, and precommitment
• Inserts commitment into state Merkle tree

Fee Structure

• Vetting fee: Configurable percentage (in basis points) taken by Entrypoint
• Example: 100 basis points = 1% fee