diff --git a/script/InteropPoW.sol b/script/InteropPoW.sol
index e59e40b..8af280a 100644
--- a/script/InteropPoW.sol
+++ b/script/InteropPoW.sol
@@ -13,7 +13,6 @@ contract InteropPoWScript is Script {
         vm.startBroadcast();
 
         bytes memory results = w.compute();
-        console.logBytes(results);
 
         vm.stopBroadcast();
     }
diff --git a/src/InteropPow.sol b/src/InteropPow.sol
index 2fb2493..7fccd7f 100644
--- a/src/InteropPow.sol
+++ b/src/InteropPow.sol
@@ -4,30 +4,72 @@ pragma solidity ^0.8.13;
 import {IL2ToL2CrossDomainMessenger} from "./interfaces.sol";
 
 interface IInteropPoW {
-    function run() external;
+    function run(uint256[] memory chainIds) external;
     function reportResults(bytes memory) external;
 
     event AllResults(bytes results);
 }
 
-// contract InteropPoW is IInteropPoW {}
+contract InteropPoW is IInteropPoW {
+    IL2ToL2CrossDomainMessenger xdm = IL2ToL2CrossDomainMessenger(0x4200000000000000000000000000000000000023);
+    address target; // TODO this should be the Worker contract, same address on all chains
+    bytes public allResults;
+
+    function run(uint256[] memory chainIds) public {
+        for (uint8 i = 0; i < chainIds.length; i++) {
+            runOnChain(chainIds[i]);
+        }
+    }
+
+    function runOnChain(uint256 chainId) public {
+        // prepare the x-domain message
+        bytes4 selector = bytes4(keccak256("run(uint256,address)"));
+        bytes memory data = abi.encodeWithSelector(selector, block.chainid, this);
+
+        // send the x-domain message
+        xdm.sendMessage(chainId, target, data);
+    }
+
+    function reportResults(bytes memory results) public {
+        // add results to global storage variable
+        for (uint256 i = 0; i < results.length; i++) {
+            allResults.push(results[i]);
+        }
+
+        // emit everything we have so far, ideally there are no duplicates
+        // (the test or script running this should check)
+        emit AllResults(allResults);
+    }
+}
 
 interface IWorker {
-    function run() external;
+    function run(uint256 returnDestination, address returnAddress) external;
 }
 
 contract Worker is IWorker {
     IL2ToL2CrossDomainMessenger xdm = IL2ToL2CrossDomainMessenger(0x4200000000000000000000000000000000000023);
-    uint256 destination; // TODO this should be the on the instigating chain
-    address target; // TODO this should be the InteropPoW contract
-
     bytes32 constant difficulty = bytes32(uint256(2 ** 250 - 1));
 
+    function run(uint256 returnDestination, address returnAddress) external {
+        // Do the computation
+        bytes memory results = compute();
+
+        // Prepare the X-domain message
+        bytes4 selector = bytes4(keccak256("sendMessage(uint256,address,bytes)"));
+        bytes memory data = abi.encodeWithSelector(selector, results);
+
+        // Send the X-domain message
+        xdm.sendMessage(returnDestination, returnAddress, data);
+    }
+
     function compute() public view returns (bytes memory) {
         bytes memory results;
-        uint8 seed = uint8(block.timestamp + uint256(blockhash(block.number - 1)));
+
+        // compute the seed, this should be unique per chain
+        bytes31 seed =
+            bytes31(bytes32(keccak256(abi.encodePacked(block.chainid, block.timestamp, blockhash(block.number - 1)))));
         for (uint8 i = 0; i < 256 - 1; i++) {
-            bytes memory preimage = bytes.concat(bytes1(seed), bytes1(i));
+            bytes memory preimage = bytes.concat(seed, bytes1(i)); // 32 bytes per solution
             bytes32 hash = keccak256(preimage);
             if (hash < difficulty) {
                 results = bytes.concat(results, preimage);
@@ -35,12 +77,4 @@ contract Worker is IWorker {
         }
         return results;
     }
-
-    function run() external {
-        bytes memory results = compute();
-        bytes4 selector = bytes4(keccak256("sendMessage(uint256,address,bytes)"));
-        bytes memory data = abi.encodeWithSelector(selector, results);
-        xdm.sendMessage(destination, target, data);
-        // TODO send results back to InteropPow contract
-    }
 }
diff --git a/test/InteropPow.t.sol b/test/InteropPow.t.sol
index 0e90f79..4640ed7 100644
--- a/test/InteropPow.t.sol
+++ b/test/InteropPow.t.sol
@@ -12,9 +12,10 @@ contract WorkerTest is Test {
     }
 
     function test_compute() public {
-        vm.warp(1641383230000);
-        bytes memory results = w.compute();
-        console.log("found %s valid preimages", results.length);
-        console.logBytes(results);
+        for (uint8 i = 0; i < 256 - 1; i++) {
+            vm.warp(i);
+            bytes memory results = w.compute();
+            console.log("found %s valid preimages", results.length / 32);
+        }
     }
 }