diff --git a/crypto/bn/bn_mul.c b/crypto/bn/bn_mul.c
index eb007e19e9a9063700ca358ab9a61e6cd3bd850e..9c4d7c71d5077d3e9421ab879a85215e8b304f38 100644
--- a/crypto/bn/bn_mul.c
+++ b/crypto/bn/bn_mul.c
@@ -61,6 +61,8 @@
 #include "bn_lcl.h"
 
 #ifdef BN_RECURSION
+/* Karatsuba-Ofman recursive multiplication algorithm */
+
 /* r is 2*n2 words in size,
  * a and b are both n2 words in size.
  * n2 must be a power of 2.