From e30d65c009e4d4a73bac9c8aa9f3b61823c7fab0 Mon Sep 17 00:00:00 2001
From: Warren Togami <wtogami@gmail.com>
Date: Mon, 19 Jan 2015 02:26:52 -1000
Subject: [PATCH] Litecoin: Disable PoW Sanity check while loading block index
 from disk.

We use the sha256 hash for the block index for performance reasons, which is recorded for later use.
CheckProofOfWork() uses the scrypt hash which is discarded after a block is accepted.
While it is technically feasible to verify the PoW, doing so takes several minutes as it
requires recomputing every PoW hash during every Litecoin startup.
We opt instead to simply trust the data that is on your local disk.
---
 src/chain.h  |  5 +++++
 src/txdb.cpp | 10 ++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/chain.h b/src/chain.h
index 6588e8f57..0c90f89be 100644
--- a/src/chain.h
+++ b/src/chain.h
@@ -276,6 +276,11 @@ public:
         return *phashBlock;
     }
 
+    uint256 GetBlockPoWHash() const
+    {
+        return GetBlockHeader().GetPoWHash();
+    }
+
     int64_t GetBlockTime() const
     {
         return (int64_t)nTime;
diff --git a/src/txdb.cpp b/src/txdb.cpp
index 078c29def..10f6465d6 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -199,8 +199,14 @@ bool CBlockTreeDB::LoadBlockIndexGuts(boost::function<CBlockIndex*(const uint256
                 pindexNew->nStatus        = diskindex.nStatus;
                 pindexNew->nTx            = diskindex.nTx;
 
-                if (!CheckProofOfWork(pindexNew->GetBlockHash(), pindexNew->nBits, Params().GetConsensus()))
-                    return error("LoadBlockIndex(): CheckProofOfWork failed: %s", pindexNew->ToString());
+                // Litecoin: Disable PoW Sanity check while loading block index from disk.
+                // We use the sha256 hash for the block index for performance reasons, which is recorded for later use.
+                // CheckProofOfWork() uses the scrypt hash which is discarded after a block is accepted.
+                // While it is technically feasible to verify the PoW, doing so takes several minutes as it
+                // requires recomputing every PoW hash during every Litecoin startup.
+                // We opt instead to simply trust the data that is on your local disk.
+                //if (!CheckProofOfWork(pindexNew->GetBlockHash(), pindexNew->nBits, Params().GetConsensus()))
+                //    return error("LoadBlockIndex(): CheckProofOfWork failed: %s", pindexNew->ToString());
 
                 pcursor->Next();
             } else {