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SHA-1 Collision Challenge

The SHA-1 Collision Challenge is a core component of Mineable UTXOs on OP_NET. It provides a unique mechanism for miners to claim rewards by solving cryptographic puzzles, contributing to both the security and utility of the network.

Understanding the Collision Challenge​

The challenge requires miners to find a solution that collides with a given preimage (preimage1) to produce the same SHA-1 hash. This solution, once found, allows the spender to unlock the associated UTXO funds.

Conditions for success

SHA1(solution) == SHA1(preimage1)

This mechanism transforms OP_NET into a dual-purpose platform, merging traditional transaction validation with cryptographic mining.

Bitcoin Script Example​

Below is a simplified Bitcoin script enforcing a SHA-1 collision challenge.

OP_2DUP          # Duplicate top two items (preimage1, preimage2)
OP_EQUAL         # Compare them. Push 1 if equal, else 0
OP_NOT           # Ensure they are distinct
OP_VERIFY        # Fail if not distinct
OP_SHA1          # Replace top stack item with SHA-1(preimage1)
OP_SWAP          # Swap top two stack items
OP_SHA1          # Replace new top stack item with SHA-1(preimage2)
OP_EQUAL         # Ensure both hashes are identical

P2SH Redeem Script Example:

OP_HASH160 <redeemScriptHash> OP_EQUAL
Redeem Script Details

The spender must reveal:

  1. The solution that collides with preimage1
  2. The redeem script itself

Solving the Collision Challenge​

Here’s a step-by-step guide to solving the challenge and claiming rewards:

// Step 1: Prepare the solution (hash collision)
const solution = Buffer.from(
  "abe4bbf04b207bffce16000fd1c3a21c019cdfbea51f86cef4789b848c0a7d5cedd3151f262c964e323c73ef2d31bee518252acec5b895543eeabc8c4059b393a582d7be38dac8b70bb437e6c01d1b4e8c61d2ba2a5b8ed3e3c0a9cf2683b78b3a479de9866e44adf5425976579483b3b4f325847ceabe4f5e18d2ad8e568c58",
  "hex"
);

// Step 2: Initialize the transaction factory
const txFactory = new TransactionFactory();

// Step 3: Generate the redeem script for the mineable reward
const redeemScript = ChallengeGenerator.generateMineableReward(
  preimage1,
  network
);

// Step 4: Fetch UTXOs (unspent transaction outputs) for the specified amount
const utxos = await provider.utxoManager.getUTXOsForAmount({
  address: redeemScript.address, // Address derived from the redeem script
  amount: 100000000n, // Required amount in satoshis
  optimize: false, // Disable optimization to fetch raw UTXOs
});

// Step 5: Prepare the last UTXO for the transaction
const lastUTXO = utxos[utxos.length - 1] as UTXO; // Select the last UTXO
lastUTXO.redeemScript = redeemScript.p2shOutputScript; // Attach the redeem script

// Step 6: Define transaction parameters for solving the challenge
const challengeSolutionParams: IChallengeSolutionTransactionParameters = {
  challengeSolution: solution, // Provide the collision solution
  from: redeemScript.address, // Address funding the transaction
  utxos: [lastUTXO], // UTXOs to be used
  amount: BigInt(minDust), // Minimum dust amount to send
  to: address.p2tr(network), // Destination address (Pay-to-Taproot in this case)
  feeRate: feeRate, // Fee rate for the transaction
  priorityFee: 0n, // Additional priority fee (none in this example)
  network: network, // Current network configuration
  signer: wallet.keypair, // Signer for the transaction
};

// Step 7: Create the transaction to solve the challenge
const fundingTransaction = await txFactory.createChallengeSolution(
  challengeSolutionParams
);

// Step 8: Broadcast the transaction to the network
const result = await Configs.RPC.sendRawTransaction({
  hexstring: fundingTransaction.tx, // Serialized transaction in hex format
});

What’s Next?​

Learn more about how to implement and optimize cross-chain mining for your network:

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