diff --git a/src/hashtree.py b/src/hashtree.py
--- a/src/hashtree.py
+++ b/src/hashtree.py
@@ -5,6 +5,10 @@ from datetime import datetime
 from util import Progress
 
 
+def hashBlock(data):
+	return hashlib.sha256(data).digest()[-HashTree.HASH_LEN:]
+
+
 class HashTree:
 	HASH_LEN=16 # bytes
 	BLOCK_SIZE=4096 # bytes
@@ -28,7 +32,7 @@ class HashTree:
 			progress=Progress(leafCount)
 			for i in range(leafCount):
 				data=f.read(HashTree.BLOCK_SIZE)
-				res.insertLeaf(hashlib.sha256(data).digest()[-HashTree.HASH_LEN:])
+				res.insertLeaf(hashBlock(data))
 
 				progress.p(i)
 			progress.done()
@@ -70,7 +74,7 @@ class HashTree:
 	## Updates the node at index and all its ancestors.
 	def updateNode(self,index):
 		while index>=0:
-			self.store[index]=hashlib.sha256(self.store[index*2+1]+self.store[index*2+2]).digest()[-HashTree.HASH_LEN:]
+			self.store[index]=hashBlock(self.store[index*2+1]+self.store[index*2+2])
 			index=(index-1)//2
 			
 	## Fast construction of the tree over the leaves. O(n).
@@ -78,14 +82,6 @@ class HashTree:
 		print(datetime.now(), "building tree:")
 		progress=Progress(-1, self.leafStart-1)
 		for i in range(self.leafStart-1,-1,-1):
-			self.store[i]=hashlib.sha256(self.store[i*2+1]+self.store[i*2+2]).digest()[-HashTree.HASH_LEN:]
+			self.store[i]=hashBlock(self.store[i*2+1]+self.store[i*2+2])
 			progress.p(i)
 		progress.done()
-
-
-if __name__=="__main__":
-	f1=HashTree.fromFile(open("serverFile.txt",mode='rb'))
-	f2=HashTree.fromFile(open("clientFile.txt",mode='rb'))
-
-	for i,(h1,h2) in enumerate(zip(f1.store,f2.store)):
-		print("{0:2}".format(i),h1.hex(),h2.hex(),h1==h2)