[Ethereum] What are the costs of using Chainlink to generate a random number using VRF

chainlinkrandomness

I'm doing some research about generating true randomness on the Ethereum blockchain.
Of course I came across Chainlink and its VRF solution.

Although there are many tutorials around, some from chainlink themselves, there is no easily available information about number generation prices (only LINK price itself) or amounts to be spent at each roll.

Does anyone who's had more experience in this know approximately how much it costs for each number roll generation?

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I've had a similar question. As far as I can tell, at the time of writing, the cost of a request to the Chainlink VRF (Verifiable Random Function) v2 on the Ethereum Mainnet is 0.25 LINK, which is around $4.

Quite expensive to pay $4 for one random number. Thoughts anyone?

Edit:

It's true that one request csts 0.25 LINK, however, it seems up to 500 random values can be requested at once, see MAX_NUM_WORDS parameter in the contract.

References

Chainlink Docs: https://docs.chain.link/docs/vrf-contracts/#config

Etherscan, see getFeeConfig: https://etherscan.io/token/0x271682DEB8C4E0901D1a1550aD2e64D568E69909#readContract

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[Ethereum] best approach for generating random NFTs

We're trying to find what you're trying to develop...

Considering NFTs have finite editions, meaning you would mint 10000 editions of 5 cards in each, you would have to pre-program amount of highest value cards (out of total 50000), the mount of second most valuable (out of total 50000) and so on. Kinda like lottery scratch cards, there would be ideally only 1 1st prize, printed on one card at the start.

If you let blockchain do it upon purchase, you might never generate the card with highest value.

Not helpful, but if you make it work or find some APP or DAPP that does that, give me a shout.

solidity – How to Request Multiple Random Numbers at Once Using Chainlink VRF

If you want to get multiple random numbers from a single VRF response, you should create an array where the randomValue is your original returned VRF number and n is the desired number of random numbers.

function expand(uint256 randomValue, uint256 n) public pure returns (uint256[] memory expandedValues) {
    expandedValues = new uint256[](n);
    for (uint256 i = 0; i < n; i++) {
        expandedValues[i] = uint256(keccak256(abi.encode(randomValue, i)));
    }
    return expandedValues;
}

This code snippet takes the initial random value, puts it inside a for loop, combines it with an incrementing number by ABI encoding the random number and incremented number, hashes that encoding using Keccak256, and finally type casts the hash to a type uint to be used as that now expanded random number. The loop then continues for as many random numbers needed, which were set with the n parameter of the function.

Reference: VRF Best Practices

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solidity – How to Request Multiple Random Numbers at Once Using Chainlink VRF

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