diff --git a/internal/crypto/crypto.go b/client/internal/oicq/ecdh.go
similarity index 83%
rename from internal/crypto/crypto.go
rename to client/internal/oicq/ecdh.go
index 4ce94ed0..492400a5 100644
--- a/internal/crypto/crypto.go
+++ b/client/internal/oicq/ecdh.go
@@ -1,4 +1,4 @@
-package crypto
+package oicq
 
 import (
 	"crypto/ecdh"
@@ -10,20 +10,17 @@ import (
 	"strconv"
 )
 
-type ECDH struct {
+// session is ecdh session in oicq.
+type session struct {
 	SvrPublicKeyVer uint16
 	PublicKey       []byte
 	ShareKey        []byte
 }
 
-type EncryptSession struct {
-	T133 []byte
-}
-
 const serverPublicKey = "04EBCA94D733E399B2DB96EACDD3F69A8BB0F74224E2B44E3357812211D2E62EFBC91BB553098E25E33A799ADC7F76FEB208DA7C6522CDB0719A305180CC54A82E"
 
-func NewECDH() *ECDH {
-	e := &ECDH{
+func newSession() *session {
+	e := &session{
 		SvrPublicKeyVer: 1,
 	}
 	key, _ := hex.DecodeString(serverPublicKey)
@@ -38,8 +35,8 @@ type pubKeyResp struct {
 	} `json:"PubKeyMeta"`
 }
 
-// FetchPubKey 从服务器获取PubKey
-func (e *ECDH) FetchPubKey(uin int64) {
+// fetchPubKey 从服务器获取PubKey
+func (e *session) fetchPubKey(uin int64) {
 	resp, err := http.Get("https://keyrotate.qq.com/rotate_key?cipher_suite_ver=305&uin=" + strconv.FormatInt(uin, 10))
 	if err != nil {
 		return
@@ -55,7 +52,7 @@ func (e *ECDH) FetchPubKey(uin int64) {
 	e.init(key) // todo check key sign
 }
 
-func (e *ECDH) init(svrPubKey []byte) {
+func (e *session) init(svrPubKey []byte) {
 	p256 := ecdh.P256()
 	local, _ := p256.GenerateKey(rand.Reader)
 	remote, _ := p256.NewPublicKey(svrPubKey)
diff --git a/client/internal/oicq/oicq.go b/client/internal/oicq/oicq.go
index a08dde78..c684108a 100644
--- a/client/internal/oicq/oicq.go
+++ b/client/internal/oicq/oicq.go
@@ -1,17 +1,16 @@
 package oicq
 
 import (
+	"crypto/rand"
 	goBinary "encoding/binary"
-	"math/rand"
 
 	"github.com/pkg/errors"
 
 	"github.com/Mrs4s/MiraiGo/binary"
-	"github.com/Mrs4s/MiraiGo/internal/crypto"
 )
 
 type Codec struct {
-	ecdh      *crypto.ECDH
+	ecdh      *session
 	randomKey []byte
 
 	WtSessionTicketKey []byte
@@ -19,11 +18,11 @@ type Codec struct {
 
 func NewCodec(uin int64) *Codec {
 	c := &Codec{
-		ecdh:      crypto.NewECDH(),
+		ecdh:      newSession(),
 		randomKey: make([]byte, 16),
 	}
 	rand.Read(c.randomKey)
-	c.ecdh.FetchPubKey(uin)
+	c.ecdh.fetchPubKey(uin)
 	return c
 }