From 91120a9a4a8594f9272e5c6378d7ef6ce9765f7b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ege=20Okan=20=C3=9Cnald=C4=B1?=
 <35339130+exeokan@users.noreply.github.com>
Date: Fri, 7 Feb 2025 17:21:15 +0300
Subject: [PATCH] Use sha2 for block hash calculation (#1823)

---
 crates/bitcoin-da/src/spec/header.rs | 38 ++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/crates/bitcoin-da/src/spec/header.rs b/crates/bitcoin-da/src/spec/header.rs
index ec2ab2359e..8170aa0c52 100644
--- a/crates/bitcoin-da/src/spec/header.rs
+++ b/crates/bitcoin-da/src/spec/header.rs
@@ -1,6 +1,7 @@
 use core::ops::Deref;
 
 use bitcoin::block::{Header as BitcoinHeader, Version};
+use bitcoin::consensus::Encodable;
 use bitcoin::hashes::Hash;
 use bitcoin::{BlockHash, CompactTarget, TxMerkleNode};
 use borsh::{BorshDeserialize, BorshSerialize};
@@ -8,6 +9,7 @@ use serde::{Deserialize, Serialize};
 use sov_rollup_interface::da::BlockHeaderTrait;
 
 use super::block_hash::BlockHashWrapper;
+use crate::helpers::calculate_double_sha256;
 
 // HeaderWrapper is a wrapper around BlockHash to implement BlockHeaderTrait
 #[derive(
@@ -33,7 +35,7 @@ impl BlockHeaderTrait for HeaderWrapper {
     }
 
     fn verify_hash(&self) -> bool {
-        self.hash() == BlockHashWrapper::from(self.header.block_hash().to_byte_array())
+        self.hash() == BlockHashWrapper(self.block_hash())
     }
 
     fn txs_commitment(&self) -> Self::Hash {
@@ -70,7 +72,11 @@ impl HeaderWrapper {
     }
 
     pub fn block_hash(&self) -> BlockHash {
-        self.header.block_hash()
+        let mut enc = vec![];
+        self.header
+            .consensus_encode(&mut enc)
+            .expect("engines don't error");
+        BlockHash::from_raw_hash(Hash::from_byte_array(calculate_double_sha256(&enc)))
     }
 
     pub fn merkle_root(&self) -> [u8; 32] {
@@ -135,3 +141,31 @@ impl From<BitcoinHeader> for BitcoinHeaderWrapper {
         Self(header)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::fs::File;
+    use std::io::{BufRead, BufReader};
+    use std::ops::Deref;
+
+    use borsh::BorshDeserialize;
+
+    use super::BitcoinHeaderWrapper;
+    use crate::spec::header::HeaderWrapper;
+
+    #[test]
+    fn calculate_block_hash() {
+        let file = File::open("test_data/testnet4/headers-40310-42346.txt").unwrap();
+        let reader = BufReader::new(file);
+        for (line, height) in reader.lines().zip(40310..=42346) {
+            let header_hex = line.unwrap();
+            let header_bytes = hex::decode(&header_hex).unwrap();
+
+            let inner_header =
+                BitcoinHeaderWrapper::deserialize(&mut header_bytes.as_ref()).unwrap();
+            let header = HeaderWrapper::new(*inner_header.deref(), 0, height, [0; 32]);
+
+            assert_eq!(inner_header.block_hash(), header.block_hash())
+        }
+    }
+}