cmd/balloon/main.go | 18 ++++++++++++++++++

diff --git a/cmd/balloon/main.go b/cmd/balloon/main.go
index ba9c14eb922716971cfe62f5e921ae0c93712e0cc7d90bd8c22a195556b014d4..9e329033a739944e827a895775520111dd236c2ed942a1879a366af36a6da570 100644
--- a/cmd/balloon/main.go
+++ b/cmd/balloon/main.go
@@ -1,3 +1,21 @@
+/*
+balloon -- Balloon password hashing function
+Copyright (C) 2016-2019 Sergey Matveev <stargrave@stargrave.org>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as
+the Free Software Foundation, version 3 of the License.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this program.  If not, see
+<http://www.gnu.org/licenses/>.
+*/
+
 package main
 
 import (