diff --git a/src/udprelay.c b/src/udprelay.c
index b6c8c8ee..d2f67ea1 100644
--- a/src/udprelay.c
+++ b/src/udprelay.c
@@ -953,16 +953,11 @@ server_recv_cb(EV_P_ ev_io *w, int revents)
      * +----+------+------+----------+----------+----------+
      *
      * shadowsocks UDP Request (before encrypted)
-     * +------+----------+----------+----------+-------------+
-     * | ATYP | DST.ADDR | DST.PORT |   DATA   |  HMAC-SHA1  |
-     * +------+----------+----------+----------+-------------+
-     * |  1   | Variable |    2     | Variable |     10      |
-     * +------+----------+----------+----------+-------------+
-     *
-     * If ATYP & ONETIMEAUTH_FLAG(0x10) != 0, Authentication (HMAC-SHA1) is enabled.
-     *
-     * The key of HMAC-SHA1 is (IV + KEY) and the input is the whole packet.
-     * The output of HMAC-SHA is truncated to 10 bytes (leftmost bits).
+     * +------+----------+----------+----------+
+     * | ATYP | DST.ADDR | DST.PORT |   DATA   |
+     * +------+----------+----------+----------+
+     * |  1   | Variable |    2     | Variable |
+     * +------+----------+----------+----------+
      *
      * shadowsocks UDP Response (before encrypted)
      * +------+----------+----------+----------+