diff --git a/sca/ascad/attack.py b/sca/ascad/attack.py
index fd217b7..d539562 100644
--- a/sca/ascad/attack.py
+++ b/sca/ascad/attack.py
@@ -91,8 +91,26 @@ def main(db):
         model[:, i] = AES_SBOX[model[:, i] ^ pt_v] ^ mask_v
     model = numpy_popcount.popcount(model).astype("double")
 
-    input_matrix = numpy.vstack((model, traces.transpose()))
-    coefs = numpy.corrcoef(input_matrix)[0:256, 256:]
+    # O - (n,t) array of n traces with t samples each
+    # P - (n,m) array of n predictions for each of the m candidates
+    # returns an (m,t) correaltion matrix of m traces t samples each
+    def corr_submatrix(O, P):
+        O -= numpy.mean(O, axis=0)
+        P -= numpy.mean(P, axis=0)
+
+        numerator = numpy.einsum("nm,nt->mt", P, O, optimize='optimal')
+        denominator = numpy.sqrt(numpy.outer((P * P).sum(axis=0), (O * O).sum(axis=0)))
+
+        return numerator / denominator
+
+    # boring, slow, uses too much RAM
+    # input_matrix = numpy.vstack((model, traces.transpose()))
+    # coefs = numpy.corrcoef(input_matrix)[0:256, 256:]
+
+    # uwu
+    coefs = corr_submatrix(traces, model.transpose())
+
+    # plot absmax
     coefs = numpy.abs(coefs)
     max_by_key = numpy.max(coefs, axis=1)
     plt.plot(max_by_key)