lib/xor.go: FixedXOR: add doc string.

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/xor.go b/lib/xor.go
index 270999c..ae2bd12 100644
--- a/lib/xor.go
+++ b/lib/xor.go
@@ -3,6 +3,7 @@
 
 package lib
 
+// Both 'a' and 'b' must be hex encoded string.
 func FixedXOR(a, b string) string {
 	cs := ""
 	if len(a) != len(b) {