VRF Oracle

ZKasino requires randomness for its games which it receives from an integrated Verifiable Random Function (VRF). A VRF is a Random Number Generator (RNG) that provides random outcomes which are verifiable on-chain. With a VRF, ZKasino is able to provide users provably fair outcomes that are impossible to have been tampered with. Chainlink VRF is the biggest VRF provider in crypto. More information on how a VRF like Chainlink VRF works, can be found here. For information on how ZKasino uses VRFs with its contracts, please see the Architecture page.

Integrated VRFs

Network	VRF integration	Subscription	Smart Contract address
Polygon	Chainlink VRF	576	0xAE975071Be8F8eE67addBC1A82488F1C24858067
Arbitrum	Chainlink VRF	53	0x41034678d6c633d8a95c75e1138a360a28ba15d1
Depreciated
Fantom	Chainlink VRF (Subscription)		VRFCoordinatorV2
BNB Chain	Chainlink VRF (Subscription)		VRFCoordinatorV2
Arbitrum	Randomizer		Randomizer: VRF

VRF fee

For VRFs to resolve RNG requests a lot of computation power is needed. Therefor, VRFs ask a fee to be paid for their efforts. The VRF fee is paid upfront by the user. Note that gas fees may seem high initially. This is because the VRF fee can only be calculated when the VRF request is made. A big portion of the VRF fee is refunded in the same transaction.

The VRF is also described in the Architecture.

Pending VRF requests

On their profile page a player can find "Pending VRF Requests". On very rare occasions the VRF request does not get resolved and the player's wager will be stuck in the game contract. After 100 blocks the player can click "Refund" to remove their wager from the game contract.

Chainlink VRF

On September 5th 2022 Chainlink announced that the Chainlink VRF had received a GLI-19 compliance certification through BMM Testlabs. This meant the first compliance certification for a VRF in the blockchain gaming industry. BMM Testlabs is an independent, gaming certification lab.