# Signature Distributor

## Introduction

The EDDSA Distributor program provides signature-based token distribution using EDDSA signatures for claim verification. This approach offers an alternative to Merkle tree-based distributors, allowing for more flexible and dynamic claim authorizations.

## 🚀 Quick Start

### What is an EDDSA Distributor?

An EDDSA Distributor is a smart contract system that enables efficient token distribution using signature verification. Instead of storing a Merkle tree root, it uses cryptographic signatures from an authorized signer to validate claims, offering greater flexibility for dynamic distributions.

### Key Benefits

* ✅ **Dynamic Claims** - No need to generate Merkle trees in advance
* ✅ **Signature-Based** - Claims authorized via EDDSA signatures
* ✅ **Batch Processing** - Process multiple claims in one transaction

### Key Differences from Merkle Distributors

| Feature      | Merkle Distributor  | EDDSA Distributor |
| ------------ | ------------------- | ----------------- |
| Verification | Merkle proofs       | EDDSA signatures  |
| Data Storage | Merkle root         | Authorized signer |
| Claim Data   | Fixed at deployment | Dynamic per claim |
| Gas Cost     | Higher for setup    | Higher per claim  |
| Flexibility  | Limited             | High              |

## 📋 System Overview

### Account Structure

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### Storage Pattern

A contract has one config storage account, which stores the contract admin's account address and the default fee collector's deployment address. This account will also store a new admin's account address for secure two-step ownership transfers.

```rust
pub struct Config {
  pub admin: Pubkey,
  pub new_admin: Pubkey,
  pub default_fee_collector: Pubkey,
}
```

An EDDSA Distributor deployment can manage multiple airdrops. Airdrops use the following storage pattern:

```rust
pub struct Airdrop {
  pub owner: Pubkey,
  pub authorized_signer: Pubkey,
  pub token: Pubkey,
  pub start_time: u64,
  pub end_time: u64,
  pub fee_collector: Pubkey,
  pub fee_token: Pubkey,
  pub paused: bool,
}
```

### Claim Mechanism

Claim support with signature verification:

```rust
pub fn claim(
  ctx: Context<Claim>,
  project_id: String,
  recipient: Pubkey,
  user_claim_id: [u8; 32],
  group: [u8; 32],
  user_claim_data: EDDSADistributorData,
  signature: Vec<u8>
) -> Result<()>
```

**Security Features**

* ECDSA signature verification
* Pausable functionality
* Reentrancy protection
* Claim ID account initialization to prevent double claims

#### Key Functions

| Function          | Description                                     |
| ----------------- | ----------------------------------------------- |
| `initialize()`    | Initialize an airdrop, create required accounts |
| `setBaseParams()` | Sets token, time window, and authorized signer  |
| `claim()`         | Processes batch claims with signatures          |
| `togglePause()`   | Emergency pause functionality                   |
| `deposit()`       | Deposit tokens to be airdropped                 |

## 🔌 Distributor Variants

### EDDSADistributor

Standard implementation for token distribution.

**Data Structure:**

```rust
pub struct EDDSADistributorData {
  pub claimable_timestamp: u64,
  pub claimable_amount: u64,
}
```

**Key Features:**

* Supports both SPL and SPL2022 tokens
* Time-locked claims based on `claimable_timestamp`
* Standard withdrawal function for unclaimed tokens

### FungibleTokenWithFeesEDDSADistributor

Extension that includes fee data in the claim structure.

**Data Structure:**

```rust
pub struct EDDSADistributorData {
  pub claimable_timestamp: u64,
  pub claimable_amount: u64,
  pub fees: u64,
}
```

**Key Features:**

* Fees encoded in claim data
* Batch fee collection
* Mandatory fee collector configuration
* Custom fee amounts per claim

## 💰 Fee System

### Overview

The fee system provides flexible fee collection for claims.

### Components

1. **Fee Collector** - External `FeeCollector` program that calculates and manages vault accounts
2. **Fee Token** - Native or SPL token for fees
3. **Vault Accounts** - Program Derived Accounts (PDAs) for holding fee tokens

### Fee Implementations

1. **Fixed Fee** - Base implementation charges per claim or batch
2. **Custom Fee** - Extension allows per-claim fee amounts

## 🔒 Security

### Access Control

| Role              | Permissions                                    |
| ----------------- | ---------------------------------------------- |
| Program Admin     | Set fee collector, transfer program admin      |
| Airdrop Owner     | Set parameters, toggle pause, configure signer |
| Authorized Signer | Sign claim authorizations                      |
| Users             | Submit claims with valid signatures            |

### Security Features

* **Signature Verification** - ECDSA signature validation
* **Pausable** - Emergency stop functionality
* **Reentrancy Guards** - Protection against reentrancy attacks
* **Claim Tracking** - Prevents double claiming
* **Time Windows** - Enforced distribution periods

## 📡 Events & Errors

### Events

| Event              | Description                      |
| ------------------ | -------------------------------- |
| `Initialized`      | Successful aidrop initialization |
| `ClaimDelegateSet` | Successful claim delegate set    |
| `Claimed`          | Successful token claim           |

### Errors

| Error                       | Condition                                                                   |
| --------------------------- | --------------------------------------------------------------------------- |
| `UnsupportedOperation`      | Operation not allowed                                                       |
| `TimeInactive`              | Outside distribution window                                                 |
| `InvalidSignature`          | Signature verification failed                                               |
| `OutsideClaimableTimeRange` | Outside claim window                                                        |
| `NotOwner`                  | Unpermissioned account trying to call an owner-permissioned function        |
| `NotProgramAdmin`           | Unpermissioned account trying to call a program admin-permissioned function |
| `NotPermissioned`           | Unpermissioned account trying to receive program admin status               |
| `InvalidFeeCollector`       | Provided fee collector account is incorrect                                 |
| `Paused`                    | Airdrop has been paused                                                     |