diff --git a/exam/ex.tex b/exam/ex.tex
index 3c543f5..1d3df4d 100644
--- a/exam/ex.tex
+++ b/exam/ex.tex
@@ -72,7 +72,9 @@
       generate multiples of the block size as outputs. The outputs are
       variable-length.
 
-    \item \TODO
+    \item EWCDM is based on a pseudorandom permutation (i.e. block cipher) and
+      an almost xor-universal (AXU) hash function (one-way function).
+
     \item \TODO
     \item \TODO
     \item \TODO