Provably Fair Minesweeper - Verify Game Fairness Using Cryptographic Commitments
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Verification
How It Works
Game Configuration
🔒 Cryptographic Commitment (SHA-256)
The server has committed to the mine positions BEFORE you play. This hash proves the game is fair!
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Play a game first, then click "Verify Game Outcome" to see the cryptographic proof!
🤔 What is a Commitment Scheme?
A commitment scheme is like putting a secret message in a sealed envelope. Once sealed,
you can't change the message inside, but you can prove later what was in the envelope all along.
In this game, the server "seals" the mine positions in a cryptographic envelope (SHA-256 hash)
BEFORE you start playing. This proves the server can't cheat by moving mines after seeing your clicks!
🎮 How This Game Uses Commitments
Step-by-step flow:
Server generates: Random seed (32 bytes) + mine positions
Server commits:commitment = SHA-256(seed + positions)
You receive: Commitment hash BEFORE playing
You play: Click tiles to reveal safe spots or mines
Game ends: Win (all safe tiles) or loss (hit mine)
Server reveals: Original seed + mine positions
You verify: Recalculate SHA-256(seed + positions)
Check match: Does it equal the original commitment? ✓ Verified!
🔐 Why SHA-256?
SHA-256 is a cryptographic hash function with special properties:
One-way: Cannot reverse the hash to find the original data
Deterministic: Same input always produces same output
Collision-resistant: Nearly impossible to find two different inputs with same hash
Avalanche effect: Tiny input change completely changes the hash
These properties make SHA-256 perfect for commitments - the server can't predict what hash
will be produced without knowing the exact data, and can't find different mine positions
that produce the same hash.
🛡️ Why Can't the Server Cheat?
The commitment scheme has a binding property:
Once the server shares the commitment hash, it's locked in
The server cannot find different mine positions that produce the same hash
If the server tries to cheat, the verification step will fail
You have the original hash saved - the server can't change it retroactively
This is mathematically guaranteed by SHA-256's collision resistance. Even with massive
computing power, finding a "fake" set of mine positions with the same hash is impossible.
🌍 Real-World Applications
Commitment schemes are used in many critical systems:
Online Gambling: Provably fair casinos use commitments to prove dice rolls, card shuffles, and slot machines aren't rigged
Voting Systems: Voters can verify their vote was counted without revealing who they voted for
Blockchain: Bitcoin and Ethereum use hash commitments to link blocks and prevent tampering
Auctions: Sealed-bid auctions where bids are committed before revealing
Timestamping: Proving a document existed at a specific time
🧪 Try It Yourself!
Play a game, then verify the outcome! The verification tab will show you:
The original commitment hash you saw before playing
The server's revealed seed and mine positions
Step-by-step hash calculation
Visual confirmation that the hashes match ✓
You can even copy the seed and positions, then use an external SHA-256 calculator
to independently verify the math. That's the beauty of cryptographic proofs - you
don't have to trust anyone!