diff --git a/common/crypto/io.go b/common/crypto/io.go
index 887532556..f5a79b288 100644
--- a/common/crypto/io.go
+++ b/common/crypto/io.go
@@ -3,21 +3,26 @@ package crypto
 import (
 	"crypto/cipher"
 	"io"
+
+	"github.com/v2ray/v2ray-core/common"
 )
 
-type cryptionReader struct {
+type CryptionReader struct {
 	stream cipher.Stream
 	reader io.Reader
 }
 
-func NewCryptionReader(stream cipher.Stream, reader io.Reader) io.Reader {
-	return &cryptionReader{
+func NewCryptionReader(stream cipher.Stream, reader io.Reader) *CryptionReader {
+	return &CryptionReader{
 		stream: stream,
 		reader: reader,
 	}
 }
 
-func (this *cryptionReader) Read(data []byte) (int, error) {
+func (this *CryptionReader) Read(data []byte) (int, error) {
+	if this.reader == nil {
+		return 0, common.ErrorAlreadyReleased
+	}
 	nBytes, err := this.reader.Read(data)
 	if nBytes > 0 {
 		this.stream.XORKeyStream(data[:nBytes], data[:nBytes])
@@ -25,19 +30,32 @@ func (this *cryptionReader) Read(data []byte) (int, error) {
 	return nBytes, err
 }
 
-type cryptionWriter struct {
+func (this *CryptionReader) Release() {
+	this.reader = nil
+	this.stream = nil
+}
+
+type CryptionWriter struct {
 	stream cipher.Stream
 	writer io.Writer
 }
 
-func NewCryptionWriter(stream cipher.Stream, writer io.Writer) io.Writer {
-	return &cryptionWriter{
+func NewCryptionWriter(stream cipher.Stream, writer io.Writer) *CryptionWriter {
+	return &CryptionWriter{
 		stream: stream,
 		writer: writer,
 	}
 }
 
-func (this *cryptionWriter) Write(data []byte) (int, error) {
+func (this *CryptionWriter) Write(data []byte) (int, error) {
+	if this.writer == nil {
+		return 0, common.ErrorAlreadyReleased
+	}
 	this.stream.XORKeyStream(data, data)
 	return this.writer.Write(data)
 }
+
+func (this *CryptionWriter) Release() {
+	this.writer = nil
+	this.stream = nil
+}