be strict w/ evalpoly to help catch the previous commit bug...

This makes sure that the coefficients and polynomial match such
that either there's enough coefficients, or the polynomial is..

shamirss.py

@@ -56,7 +56,8 @@ def _makered(x, y):
 	return x
 
 def evalpoly(polynomial, powers):
-	return sum(( x * y for x, y in zip(polynomial, powers)), 0)
+	return sum(( x * y for x, y in zip(polynomial, powers,
+	    strict=True)), 0)
 
 def create_shares(data, k, nshares):
 	'''Given data, create nshares, such that given any k shares,
@@ -197,7 +198,7 @@ class TestShamirSS(unittest.TestCase):
 	def test_evalpoly(self):
 		a = GF2p8(random.randint(0, 255))
 
-		powers = a.powerseries(5)
+		powers = a.powerseries(4)
 
 		self.assertTrue(all(isinstance(x, GF2p8) for x in powers))
 
@@ -207,10 +208,12 @@ class TestShamirSS(unittest.TestCase):
 		self.assertEqual(r, vals[0] + vals[1] * powers[1] + vals[2] *
 		    powers[2] + vals[3] * powers[3] + vals[4] * powers[4])
 
-		r = evalpoly(vals[:3], powers)
+		r = evalpoly(vals[:3], powers[:3])
 		self.assertEqual(r, vals[0] + vals[1] * powers[1] + vals[2] *
 		    powers[2])
 
+		self.assertRaises(ValueError, evalpoly, [1], [1, 2])
+
 	def test_create_shares(self):
 		self.assertRaises(TypeError, create_shares, '', 1, 1)