Blackjack

Provably fair

Verify fairness

The session's seed decides every card. Its hash was committed before the first hand; the seed is revealed when the session ends. Each round's cards come from HMAC-SHA256 keyed by the seed over the round's number and the bettor's own seed.

Seed hash

d89cdc72de378b6030d20c688ceab0aaa867fcf70f2a6bd085f8d93f2e7b4cce

Seed

25d84902cd10640e90b31438108d79445bc0e86e0e82684b6e01db003ea13454 SHA-256 of "degen.match.seed.v1", a zero byte and the 32 seed bytes is the seed hash.

Bettor's seed

e4df32370fa04a8225a5698ac61cbb29

Commitment

Batch 55,880, Merkle root 0c49e1eee208a31813596a32a383236618065b3b1d99653bc01380e8a902f9c8. Recorded by Degen Protocol, not on a chain. See this batch and its Merkle tree

Merkle path

1. f84bb8128ac44ce7489c70b8016274d91fb40c67c9aedfb95171df7c804b1591
2. 90c7ad4b1c29a66560aecc04c22ecccc3b9b48118017e00e677c8f6c1b854f41
3. 18ef2638d4e42427481de5087ce57c4e585f4ebfa24d2f2d4105d66101c4d9b9

Checked: the seed hash proves into the root.

To check it yourself, take the session's proof:

1. Hash the seed as above and compare it with the seed hash; prove the seed hash into the root with the Merkle path (keccak256, as for every match).
2. For each round: round seed = HMAC-SHA256(key = seed, "degen.house.round.v1" ‖ 0x00 ‖ u64be(length of the bettor's seed) ‖ bettor's seed ‖ u64be(round)).
3. Key ChaCha20 (RFC 8439, zero nonce) with the round seed and read little-endian 64-bit words; a card is the next word below 2⁶⁴ − 1 − ((2⁶⁴ − 1) mod 52), modulo 52.
4. Replay the round's actions with the game's rules: the cards and the payout must match.

The replay plays every hand rebuilt this way on the server from the same data, and marks any that does not rebuild as recorded.