---
name: cartridge-vrf-integration
description: "Integrate Cartridge's Verifiable Random Function (VRF) for provably fair, atomic randomness in Dojo games."
---

# Cartridge VRF Integration

Integrate Cartridge's Verifiable Random Function (VRF) for provably fair, atomic randomness in Dojo games.

## Overview

Cartridge VRF provides cheap, atomic verifiable randomness for fully onchain games. The VRF request and response are processed within the **same transaction**, enabling synchronous and immediate randomness.

## Contract Addresses

| Network | Contract Address |
|---------|-----------------|
| Mainnet | `0x051fea4450da9d6aee758bdeba88b2f665bcbf549d2c61421aa724e9ac0ced8f` |
| Sepolia | `0x051fea4450da9d6aee758bdeba88b2f665bcbf549d2c61421aa724e9ac0ced8f` |

## Installation

Add to your `Scarb.toml`:

```toml
[dependencies]
cartridge_vrf = { git = "https://github.com/cartridge-gg/vrf" }
```

## Cairo Integration

### 1. Import the VRF Provider

```cairo
use cartridge_vrf::IVrfProviderDispatcher;
use cartridge_vrf::IVrfProviderDispatcherTrait;
use cartridge_vrf::Source;
```

### 2. Define VRF Provider Address

```cairo
// Use the deployed VRF provider address
const VRF_PROVIDER_ADDRESS: felt252 = 0x051fea4450da9d6aee758bdeba88b2f665bcbf549d2c61421aa724e9ac0ced8f;
```

### 3. Consume Random Values

```cairo
#[dojo::contract]
mod game_system {
    use starknet::{ContractAddress, get_caller_address};
    use cartridge_vrf::{IVrfProviderDispatcher, IVrfProviderDispatcherTrait, Source};

    const VRF_PROVIDER_ADDRESS: felt252 = 0x051fea4450da9d6aee758bdeba88b2f665bcbf549d2c61421aa724e9ac0ced8f;

    #[abi(embed_v0)]
    impl GameImpl of IGame<ContractState> {
        fn roll_dice(ref self: ContractState) -> u8 {
            let vrf_provider = IVrfProviderDispatcher { 
                contract_address: VRF_PROVIDER_ADDRESS.try_into().unwrap() 
            };
            
            let player = get_caller_address();
            
            // Consume random value using player's nonce
            let random_value: felt252 = vrf_provider.consume_random(Source::Nonce(player));
            
            // Convert to dice roll (1-6)
            let random_u256: u256 = random_value.into();
            let dice_roll: u8 = (random_u256 % 6 + 1).try_into().unwrap();
            
            dice_roll
        }
    }
}
```

## Source Types

Two source types for randomness:

### `Source::Nonce(ContractAddress)`
- Uses the address's internal nonce
- Each request generates a unique seed
- **Recommended for most use cases**

```cairo
let random = vrf_provider.consume_random(Source::Nonce(player_address));
```

### `Source::Salt(felt252)`
- Uses a provided salt value
- Same salt = same random value
- Useful for deterministic scenarios

```cairo
let random = vrf_provider.consume_random(Source::Salt(game_id));
```

## Client-Side Integration (JavaScript/TypeScript)

When executing transactions that use VRF, prefix with `request_random`:

```typescript
import { Account, CallData } from "starknet";

const VRF_PROVIDER = "0x051fea4450da9d6aee758bdeba88b2f665bcbf549d2c61421aa724e9ac0ced8f";

async function rollDice(account: Account, gameContract: string) {
  const call = await account.execute([
    // First: request_random
    {
      contractAddress: VRF_PROVIDER,
      entrypoint: "request_random",
      calldata: CallData.compile({
        caller: gameContract,
        source: [0, account.address], // Source::Nonce(address)
      }),
    },
    // Then: your game action
    {
      contractAddress: gameContract,
      entrypoint: "roll_dice",
      calldata: [],
    },
  ]);
  
  return call;
}
```

### Using Dojo SDK

```typescript
import { buildVrfCalls } from "@cartridge/vrf";

const calls = await buildVrfCalls({
  account,
  call: {
    contractAddress: GAME_CONTRACT,
    entrypoint: "roll_dice",
    calldata: [],
  },
  vrfProviderAddress: VRF_PROVIDER,
});

await account.execute(calls);
```

## How It Works

1. Game calls `request_random(caller, source)` as **first call** in multicall
2. Game contract calls `consume_random(source)` internally
3. VRF server generates random value using VRF algorithm
4. Cartridge Paymaster wraps multicall with `submit_random` and `assert_consumed`
5. Proof verified onchain, random value immediately available
6. `assert_consumed` ensures `consume_random` was called and resets storage

## Testing with Mock Provider

For local development/testing, use the mock provider:

```cairo
#[dojo::contract]
mod vrf_provider_mock {
    use cartridge_vrf::PublicKey;
    use cartridge_vrf::vrf_provider::vrf_provider_component::VrfProviderComponent;
    use openzeppelin::access::ownable::OwnableComponent;

    component!(path: OwnableComponent, storage: ownable, event: OwnableEvent);
    component!(path: VrfProviderComponent, storage: vrf_provider, event: VrfProviderEvent);

    #[abi(embed_v0)]
    impl VrfProviderImpl = VrfProviderComponent::VrfProviderImpl<ContractState>;

    #[storage]
    pub struct Storage {
        #[substorage(v0)]
        ownable: OwnableComponent::Storage,
        #[substorage(v0)]
        vrf_provider: VrfProviderComponent::Storage,
    }

    fn dojo_init(ref self: ContractState, pubkey_x: felt252, pubkey_y: felt252) {
        self.ownable.initializer(starknet::get_caller_address());
        self.vrf_provider.initializer(PublicKey { x: pubkey_x, y: pubkey_y });
    }
}
```

## Common Patterns

### Random Number in Range

```cairo
fn random_in_range(random: felt252, min: u32, max: u32) -> u32 {
    let random_u256: u256 = random.into();
    let range = max - min + 1;
    let result: u32 = (random_u256 % range.into()).try_into().unwrap();
    result + min
}
```

### Weighted Random Selection

```cairo
fn weighted_random(random: felt252, weights: Span<u32>) -> u32 {
    let total_weight: u32 = weights.iter().sum();
    let random_u256: u256 = random.into();
    let threshold: u32 = (random_u256 % total_weight.into()).try_into().unwrap();
    
    let mut cumulative: u32 = 0;
    let mut i: u32 = 0;
    loop {
        cumulative += *weights.at(i);
        if cumulative > threshold {
            break i;
        }
        i += 1;
    }
}
```

### Shuffle Array (Fisher-Yates)

```cairo
fn shuffle<T, impl TCopy: Copy<T>, impl TDrop: Drop<T>>(
    ref arr: Array<T>,
    vrf_provider: IVrfProviderDispatcher,
    player: ContractAddress,
) {
    let mut i = arr.len();
    loop {
        if i <= 1 {
            break;
        }
        i -= 1;
        let random = vrf_provider.consume_random(Source::Nonce(player));
        let j: u32 = (random.into() % (i + 1).into()).try_into().unwrap();
        // Swap arr[i] and arr[j]
        let temp = *arr.at(i);
        arr.set(i, *arr.at(j));
        arr.set(j, temp);
    };
}
```

## Important Notes

- **Always** match `Source` in `request_random` and `consume_random`
- `consume_random` must be called within the same transaction
- The Paymaster handles proof submission automatically
- Works with Cartridge Controller out of the box

## Resources

- GitHub: https://github.com/cartridge-gg/vrf
- Voyager (Mainnet): https://voyager.online/contract/0x051fea4450da9d6aee758bdeba88b2f665bcbf549d2c61421aa724e9ac0ced8f
- Voyager (Sepolia): https://sepolia.voyager.online/contract/0x051fea4450da9d6aee758bdeba88b2f665bcbf549d2c61421aa724e9ac0ced8f


---
Source attribution: dojoengine
Original project: https://github.com/dojoengine/book/blob/093849a7a6fd14955581587a8575634b8db15bbf/skills/dojo-vrf/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Dave AI.

## Upstream license notice

MIT License

Copyright (c) 2023 Dojo

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Dave AI resource metadata

Creator / publisher: dojoengine
Original project: https://github.com/dojoengine/book/blob/093849a7a6fd14955581587a8575634b8db15bbf/skills/dojo-vrf/SKILL.md
Attribution basis: Source repository record

Fields of work: Development & Engineering
Roles: Backend Developer, Game Developer
Specialties: Backend
Tools: Docker, GitHub
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: c26ef3e530122ef806723870dfe41b4f5f8d48bf2cbffee157e273c36dd9ccad