escrow-contract.cash

pragma cashscript ^0.7.5;

 /**
 * @title Escrow Contract
 * An escrow is a financial arrangement where a third party holds and regulates the payment 
 * of funds required for two parties involved in a transaction. The funds are held by the 
 * escrow service until it is confirmed that all of the terms of an agreement between the buyer 
 * and seller have been met, at which point the funds are released.
 * @dev The arbiter is a person or entity that is appointed or selected to act as a neutral and 
 * impartial third party in a dispute or conflict.
 * @dev The arbiter can transfer funds to only either the seller or buyer.
 * @dev The seller has the authority to 'release' the funds directly to the buyer.
 * @dev The seller can only 'release' the funds to the buyer and not to any other address.
 * @dev The buyer cannot interact with the contract.
 * @param arbiter The public key hash of arbiter.
 * @param buyer The public key hash of buyer.
 * @param seller The public key hash of seller.
 */

contract Escrow(bytes20 arbiter, bytes20 buyer, bytes20 seller) {

    /**
     * Releases the funds to the buyer.
     * @dev Limits the number of input and output to 1.
     * @dev Fails if the caller is neither the arbiter nor the seller.
     * @dev Fails if the transaction amount is insufficient or incorrect.
     * @dev Fails if the recipient is not buyer.
     * @param pk The public key of the arbiter.
     * @param s The signature of the arbiter.
     */
    function release(pubkey pk, sig s) {
        // Requires that caller is only either the arbiter or the seller
        require(hash160(pk) == arbiter || hash160(pk) == seller);
        require(checkSig(s, pk));

        // Require input & output count to 1
        require(tx.inputs.length == 1);
        require(tx.outputs.length == 1);

        // Checks that the correct amount is sent
        int minerFee = 1000; // hardcoded fee
        int amount = tx.inputs[this.activeInputIndex].value - minerFee;
        require(tx.outputs[0].value == amount);

        // Requires that recipient is buyer
        bytes25 buyerLock = new LockingBytecodeP2PKH(buyer);
        bool sendsToBuyer = tx.outputs[0].lockingBytecode == buyerLock;
        require(sendsToBuyer);
    }

    /**
     * Refunds the funds back to the seller.
     * @dev Limits the number of input and output to 1.
     * @dev Fails if caller is not arbiter.
     * @dev Fails if amount is insufficient or incorrect.
     * @dev Fails if the recipient is not the seller.
     * @param pk The public key of the arbiter.
     * @param s The signature of the arbiter.
     */
    function refund(pubkey pk, sig s) {
        // Requires that caller is the arbiter 
        require(hash160(pk) == arbiter);
        require(checkSig(s, pk));

        // Require input & output count to 1
        require(tx.inputs.length == 1);
        require(tx.outputs.length == 1);

        // Checks that the correct amount is sent
        int minerFee = 1000; // hardcoded fee
        int amount = tx.inputs[this.activeInputIndex].value - minerFee;
        require(tx.outputs[0].value == amount);

        // Requires that recipient is seller
        bytes25 sellerLock = new LockingBytecodeP2PKH(seller);
        bool sendsToSeller = tx.outputs[0].lockingBytecode == sellerLock;
        require(sendsToSeller);
    }
}