diff --git a/cmd/vtun.go b/cmd/vtun.go
index e4bd452..740f7c7 100644
--- a/cmd/vtun.go
+++ b/cmd/vtun.go
@@ -8,7 +8,7 @@ import (
 	"os/exec"
 	"runtime"
 
-	"github.com/net-byte/vtun/util"
+	"github.com/net-byte/vtun/common/cipher"
 	"github.com/songgao/water"
 )
 
@@ -24,7 +24,7 @@ func New(local *string, remote *string, port *int, key *string) {
 		log.Fatal("Only support linux!")
 		return
 	}
-	hashKey := util.CreateHash(*key)
+	hashKey := cipher.CreateHash(*key)
 	// create tun
 	config := water.Config{
 		DeviceType: water.TAP,
@@ -64,7 +64,7 @@ func New(local *string, remote *string, port *int, key *string) {
 			}
 			b := buf[:n]
 			// decrypt data
-			util.Decrypt(&b, hashKey)
+			cipher.Decrypt(&b, hashKey)
 			iface.Write(b)
 		}
 	}()
@@ -77,7 +77,7 @@ func New(local *string, remote *string, port *int, key *string) {
 		}
 		b := packet[:n]
 		// encrypt data
-		util.Encrypt(&b, hashKey)
+		cipher.Encrypt(&b, hashKey)
 		conn.WriteToUDP(b, remoteAddr)
 	}
 }
@@ -95,6 +95,6 @@ func execCmd(c string, args ...string) {
 	cmd.Stdin = os.Stdin
 	err := cmd.Run()
 	if nil != err {
-		log.Fatalln("Error running /sbin/ip:", err)
+		log.Fatalln("Exec /sbin/ip error:", err)
 	}
 }
diff --git a/util/cipher.go b/common/cipher/cipher.go
similarity index 97%
rename from util/cipher.go
rename to common/cipher/cipher.go
index 077e276..80f719e 100644
--- a/util/cipher.go
+++ b/common/cipher/cipher.go
@@ -1,4 +1,4 @@
-package util
+package cipher
 
 import (
 	"crypto/sha256"
diff --git a/go.mod b/go.mod
index 65d7371..7b2ea45 100644
--- a/go.mod
+++ b/go.mod
@@ -5,5 +5,4 @@ go 1.16
 require (
 	github.com/songgao/water v0.0.0-20200317203138-2b4b6d7c09d8
 	golang.org/x/crypto v0.0.0-20190829043050-9756ffdc2472
-	golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3
 )