From 01ba23c35764595be8a79f419233856b5c33f04c Mon Sep 17 00:00:00 2001
From: Daniel Wang <99078276+dantaik@users.noreply.github.com>
Date: Wed, 15 Feb 2023 11:21:24 +0800
Subject: [PATCH] fix(protocol): make mixHash have random number from
 beaconchain (#13156)

---
 packages/protocol/contracts/L1/libs/LibProposing.sol | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/packages/protocol/contracts/L1/libs/LibProposing.sol b/packages/protocol/contracts/L1/libs/LibProposing.sol
index 3ce587aff3c..0377f88669e 100644
--- a/packages/protocol/contracts/L1/libs/LibProposing.sol
+++ b/packages/protocol/contracts/L1/libs/LibProposing.sol
@@ -109,9 +109,13 @@ library LibProposing {
             meta.l1Hash = blockhash(block.number - 1);
             meta.timestamp = uint64(block.timestamp);
 
-            // if multiple L2 blocks included in the same L1 block,
-            // their block.mixHash fields for randomness will be the same.
-            meta.mixHash = bytes32(block.difficulty);
+            // After The Merge, mixHash contains the prevrandao
+            // from the beacon chain. Since multiple Taiko blocks
+            // can be proposed in one Ethereum block, we need to
+            // add salt to this random number.
+            meta.mixHash = keccak256(
+                abi.encodePacked(block.prevrandao, state.nextBlockId)
+            );
         }
 
         uint256 deposit;