From b008cd03889e0cd88e00935efc43d07876162e25 Mon Sep 17 00:00:00 2001
From: Mike Hearn <hearn@google.com>
Date: Fri, 6 Apr 2012 18:41:40 +0200
Subject: [PATCH] Don't validate difficulty transitions on the testnet as there
 was a recent rule change, and nobody cares about security on testnet anyway.

---
 .../java/com/google/bitcoin/core/BlockChain.java   |  3 ++-
 .../com/google/bitcoin/core/NetworkParameters.java | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/com/google/bitcoin/core/BlockChain.java b/core/src/main/java/com/google/bitcoin/core/BlockChain.java
index 14af14f5..36a77899 100644
--- a/core/src/main/java/com/google/bitcoin/core/BlockChain.java
+++ b/core/src/main/java/com/google/bitcoin/core/BlockChain.java
@@ -207,7 +207,8 @@ public class BlockChain {
             // Create a new StoredBlock from this block. It will throw away the transaction data so when block goes
             // out of scope we will reclaim the used memory.
             StoredBlock newStoredBlock = storedPrev.build(block);
-            checkDifficultyTransitions(storedPrev, newStoredBlock);
+            if (params.checkBlockDifficulty)
+                checkDifficultyTransitions(storedPrev, newStoredBlock);
             blockStore.put(newStoredBlock);
             connectBlock(newStoredBlock, storedPrev, block.transactions);
         }
diff --git a/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java b/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java
index c0119672..00c3a01c 100644
--- a/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java
+++ b/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java
@@ -94,6 +94,11 @@ public class NetworkParameters implements Serializable {
      * signatures using it.
      */
     public byte[] alertSigningKey;
+    /**
+     * Whether to check block difficulty on this network. The rules for testnet have changed and become
+     * quite complicated, so don't bother verifying them. It's only a useful security check on the main network.
+     */
+    public boolean checkBlockDifficulty;
 
     /**
      * See getId(). This may be null for old deserialized wallets. In that case we derive it heuristically
@@ -153,6 +158,7 @@ public class NetworkParameters implements Serializable {
         n.genesisBlock.setDifficultyTarget(0x1d07fff8L);
         n.genesisBlock.setNonce(384568319);
         n.id = ID_TESTNET;
+        n.checkBlockDifficulty = false;
         String genesisHash = n.genesisBlock.getHashAsString();
         checkState(genesisHash.equals("00000007199508e34a9ff81e6ec0c477a4cccff2a4767a8eee39c11db367b008"),
                 genesisHash);
@@ -182,6 +188,7 @@ public class NetworkParameters implements Serializable {
         n.genesisBlock.setTime(1231006505L);
         n.genesisBlock.setNonce(2083236893);
         n.id = ID_PRODNET;
+        n.checkBlockDifficulty = true;
         String genesisHash = n.genesisBlock.getHashAsString();
         checkState(genesisHash.equals("000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"),
                 genesisHash);
@@ -197,6 +204,7 @@ public class NetworkParameters implements Serializable {
         n.genesisBlock.setDifficultyTarget(Block.EASIEST_DIFFICULTY_TARGET);
         n.interval = 10;
         n.targetTimespan = 200000000;  // 6 years. Just a very big number.
+        n.checkBlockDifficulty = true;
         n.id = "com.google.bitcoin.unittest";
         return n;
     }
@@ -216,6 +224,12 @@ public class NetworkParameters implements Serializable {
         return id;
     }
 
+    public boolean equals(Object other) {
+        if (!(other instanceof NetworkParameters)) return false;
+        NetworkParameters o = (NetworkParameters) other;
+        return o.getId().equals(getId());
+    }
+
     /** Returns the network parameters for the given string ID or NULL if not recognized. */
     public static NetworkParameters fromID(String id) {
         if (id.equals(ID_PRODNET)) {