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0xPrivacy Casino - Custom Nostr Event Kinds

Kind 8867: Casino Game Result

draft optional

A regular event (kind 8867) used by the 0xPrivacy Casino to record provably-fair casino game outcomes on the Nostr network. Each event represents a single game round and contains all the data needed to independently verify the outcome.

Event Format

{
  "kind": 8867,
  "content": "<JSON string with game data>",
  "tags": [
    ["t", "casino"],
    ["t", "<game-type>"],
    ["t", "<result>"],
    ["amount", "<bet-in-sats>"],
    ["payout", "<payout-in-sats>"],
    ["alt", "<human-readable summary>"]
  ]
}

Tags (required)

Tag Description
t "casino" - Identifies the event as a casino game result
t Game type: "slots", "dice", "roulette", "blackjack", "coinflip"
t Result: "win" or "loss"
amount Bet amount in satoshis
payout Payout amount in satoshis (0 for losses)
alt Human-readable summary of the game outcome (NIP-31 style)

Content

The .content field is a JSON string containing game-specific data and provably-fair verification information:

{
  "game": "slots",
  "bet": 1000,
  "payout": 5000,
  "multiplier": 5,
  "serverSeed": "<hex-encoded server seed>",
  "clientSeed": "<hex-encoded client seed>",
  "nonce": 42
}

Content Fields

Field Type Description
game string Game type identifier
bet number Bet amount in satoshis
payout number Amount won in satoshis (0 for losses)
multiplier number Win multiplier applied (0 for losses)
serverSeed string Server seed used for provably-fair RNG
clientSeed string Client seed used for provably-fair RNG
nonce number Nonce value for the specific game round

Additional game-specific fields may be present depending on the game type.

Game-Specific Extra Fields

Slots:

  • reels: Array of emoji symbols shown on each reel

Dice:

  • roll: The dice roll result (1-100)
  • target: The target number
  • mode: "under" or "over"

Roulette:

  • result: The winning number (0-36)
  • color: "red", "black", or "green"
  • bets: Array of placed bets

Blackjack:

  • playerValue: Final hand value of the player
  • dealerValue: Final hand value of the dealer

Coin Flip:

  • result: "heads" or "tails"
  • choice: The player's chosen side

Provably Fair Verification

Game outcomes are determined using SHA-256:

outcome = SHA-256(serverSeed + ":" + clientSeed + ":" + nonce)

The first 4 bytes of the hash are converted to a 32-bit unsigned integer and normalized to [0, 1) to determine the game result. This allows anyone to independently verify that the outcome was fair by re-computing the hash.

Querying

To fetch casino game results:

{
  "kinds": [8867],
  "#t": ["casino"],
  "limit": 50
}

To fetch a specific game type:

{
  "kinds": [8867],
  "#t": ["casino", "slots"],
  "limit": 20
}

To fetch a specific user's history:

{
  "kinds": [8867],
  "authors": ["<pubkey>"],
  "#t": ["casino"],
  "limit": 20
}

Revenue Model

All wagers carry a 2.5% total rake:

  • 2.0% goes to the house prize pool (funds player winnings)
  • 0.5% goes to the developer fund

The effective payout multiplier is calculated as:

effectivePayout = (betAmount - rake) * multiplier

Relationship to Other NIPs

  • NIP-60 (Cashu Wallet): The casino uses Cashu ecash (Chaumian Ecash) for deposits and withdrawals. Player balances are stored client-side as Cashu proofs.
  • NIP-87 (Cashu Discoverability): Mints used by the casino can be discovered via NIP-87 events.
  • NIP-61 (Nutzaps): Future integration could allow nutzaps as a deposit mechanism.

Example Events

Slots Win

{
  "kind": 8867,
  "content": "{\"game\":\"slots\",\"bet\":1000,\"payout\":4875,\"multiplier\":5,\"serverSeed\":\"a1b2c3...\",\"clientSeed\":\"d4e5f6...\",\"nonce\":7,\"reels\":[\"cherry\",\"cherry\",\"cherry\"]}",
  "tags": [
    ["t", "casino"],
    ["t", "slots"],
    ["t", "win"],
    ["amount", "1000"],
    ["payout", "4875"],
    ["alt", "0xPrivacy Casino - slots: cherry cherry cherry (won 4875 sats)"]
  ]
}

Dice Loss

{
  "kind": 8867,
  "content": "{\"game\":\"dice\",\"bet\":500,\"payout\":0,\"multiplier\":0,\"serverSeed\":\"f1e2d3...\",\"clientSeed\":\"c4b5a6...\",\"nonce\":12,\"roll\":67,\"target\":50,\"mode\":\"under\"}",
  "tags": [
    ["t", "casino"],
    ["t", "dice"],
    ["t", "loss"],
    ["amount", "500"],
    ["payout", "0"],
    ["alt", "0xPrivacy Casino - dice: rolled 67 (under 50) (lost)"]
  ]
}