Video Poker PF

• client seed: a string chosen by the player (or automatically generated if you don't choose one)

• server seed: 64-hex string generated using crypto.randomBytes(32) and hashed with SHA-256, used as 'key' for HMAC

• nonce: the number of round you're on, increases by 1 for every round across all house games

• cursor: internal number representing a nonce within the round, in video poker – it increments with every shuffle. given 52 cards, the shuffle needs 51 steps, so cursor starts at 0 and goes up to 50

• HMAC: cryptographic function that mixes unhashed server seed, client seed, nonce and cursor to produce a result

here's a 3rd party HMAC tool to verify each step for yourself: https://cryptii.com/pipes/hmac - (or any other one you prefer)

Video poker uses the "Fisher-Yates" shuffling method to shuffle cards from 0- 51, each corresponding to a playing card in a standard deck.

these are shuffled one by one for every round, with the "cursor" increasing for each shuffle

the final outcome is a result of your server & client seed combination – meaning there's no possible way for us to influence your odds

unhashed server seed:

095d6816179b10fb2edaa28f5ca48260a09045ed00d6529621fe037e5ba9d0b7

client seed: u6bEgvYMZivkzbAv

nonce: 3693

cursor: 0 (starts at 0 for each round, ends at 50)

for each shuffle, the code generates this 'message' for the HMAC input:

<clientSeed:nonce:cursor> = u6bEgvYMZivkzbAv:3693:0 (second shuffle would be u6bEgvYMZivkzbAv:3693:1)

the "key" part is your unhashed server seed

if you're using the 3rd party site above to follow along it would look like this:

these values result in the following hexadecimal string: 283703451a2dd0ab4232417789ff2a4bf7def1f06eb149be60fb0ab0ea02bc9b

each string is sampled 4 bytes (8 hex) at a time, in this case the first 4 bytes would be "28370345"

this is then converted from hexadecimal → decimal (28370345 → 674693957) this is the number we're left with for calculating the 1st shuffle: 674693957

the decimal number is ran through a modulo calculation to determine which card to use for shuffling, this looks like:

674693957 % 52 = 41 (meaning 'if you divide x by 52, what number is left over')

here's how the cards are laid out before shuffling:

deck order after first shuffle:

next shuffle uses u6bEgvYMZivkzbAv:3693:1 as the "message" part, which gives 2280786805 as the decimal number

since the 52nd slot is already decided, the calculation is 2280786805 % 51 = 46 (next one would be x % 50 etc.)

deck order after second shuffle:

the deck is then shuffled 49 more times, after which the final sequence looks like this:

after all shuffles are done, the first 10 cards of the final sequence are used as the results, so your first hand would be: AH, 5D, 2H, 3H, 7H.

no matter what cards you choose to keep, the following cards will always be the next 5 in the sequence, which in this case are: JH, 8C, 4H, 2S, 3C.
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if you were to discard the 5 of diamonds from the first hand, you'd be left with a flush, this can be verified on the fairness page - https://duel.com/fairness/verify

• pf in video poker works by combining your client seed, server seed, nonce and cursor in HMAC to shuffle numbers corresponding to playing cards in a random and unpredictable way
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• final cards are already determined before you press play
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• "Fisher-Yates" shuffling method is used for the final positions - meaning that for each round, the deck is shuffled one card at a time, 51 times, and the resulting sequence of numbers dictates if you get royal flush or not
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• as long as you're able to set a client seed (after the hashed server seed is revealed), there's nothing the casino can do to fuck with the odds without players immediately noticing
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• every individual shuffle can be verified through 3rd party tools online, no need to blindly trust Duel