diff --git a/proofow.py b/proofow.py
index 5c049a5..e25c5f7 100644
--- a/proofow.py
+++ b/proofow.py
@@ -3,10 +3,11 @@ from itertools import count
 from hashlib import sha256
 
 
-class proofow:
+
+class pow_base:
     def __init__(self, difficulty, base=None):
-        self._base = urandom(32) if not base else base
-        self._target = 2 ** (256 - difficulty)
+        self._base = urandom(self._bits//8) if not base else base
+        self._target = 2 ** (self._bits - difficulty)
 
     def work(self):
         for nonce in count():
@@ -14,5 +15,17 @@ class proofow:
                 return nonce
 
     def verify(self, nonce):
-        hexresult = sha256(self._base + str(nonce).encode()).hexdigest()
+        hexresult = self._hexdigest(self._base + str(nonce).encode())
         return int(hexresult, 16) < self._target
+
+
+
+class pow_hashlib_base(pow_base):
+    def _hexdigest(self, data):
+        return self._hasher(data).hexdigest()
+
+
+
+class pow256(pow_hashlib_base):
+    _bits = 256
+    _hasher = sha256