diff --git a/src/hashtree.py b/src/hashtree.py
--- a/src/hashtree.py
+++ b/src/hashtree.py
@@ -14,15 +14,16 @@ class HashTree:
 		self.leafCount=leafCount
 		
 	@classmethod
-	def fromFile(cls,fd):
-		stat=os.fstat(fd.fileno())
-		size=stat.st_size # !! symlinks
-		leafCount=(size-1)//HashTree.BLOCK_SIZE+1 # number of leaf blocks
-		res=cls(leafCount)
-		
-		for i in range(leafCount):
-			data=fd.read(HashTree.BLOCK_SIZE)
-			res.insertLeaf(hashlib.sha256(data).digest()[HashTree.HASH_LEN:])
+	def fromFile(cls,filename):
+		with open(filename,"rb") as f:
+			stat=os.fstat(f.fileno())
+			size=stat.st_size # !! symlinks
+			leafCount=(size-1)//HashTree.BLOCK_SIZE+1 # number of leaf blocks
+			res=cls(leafCount)
+
+			for i in range(leafCount):
+				data=f.read(HashTree.BLOCK_SIZE)
+				res.insertLeaf(hashlib.sha256(data).digest()[HashTree.HASH_LEN:])
 		res.buildTree()
 		
 		return res