diff --git a/src/hashtree.py b/src/hashtree.py
--- a/src/hashtree.py
+++ b/src/hashtree.py
@@ -1,4 +1,5 @@
-import hashlib
+import collections
+import hashlib
 import os
 from datetime import datetime
 
@@ -85,3 +86,19 @@ class HashTree:
 			self.store[i]=hashBlock(self.store[i*2+1]+self.store[i*2+2])
 			progress.p(i)
 		progress.done()
+
+	## Update faster than repeated insertLeaf.
+	def batchUpdate(self,keysHashes):
+		queue=collections.deque()
+		for (k,v) in sorted(keysHashes):
+			self.store[k]=v
+			parentK=(k-1)//2
+			if len(queue)==0 or queue[-1]!=parentK:
+				queue.append(parentK)
+
+		while len(queue)>0:
+			k=queue.pop()
+			self.store[k]=hashBlock(self.store[k*2+1]+self.store[k*2+2])
+			parentK=(k-1)//2
+			if (len(queue)==0 or queue[0]!=parentK) and k!=0:
+				queue.appendleft(parentK)