diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 718b596..4fea814 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
       - name: Get dependencies
         run: go mod tidy
       
-      - name: Enable Debug Log
+      - name: Enable debug log
         run: sed -i 's/false/true/g' config/global.go
 
       - name: Build
diff --git a/gold/head/flags.go b/gold/head/flags.go
new file mode 100644
index 0000000..de3cc56
--- /dev/null
+++ b/gold/head/flags.go
@@ -0,0 +1,34 @@
+package head
+
+import "encoding/binary"
+
+type PacketFlags uint16
+
+func (pf PacketFlags) IsValid() bool {
+	return pf&0x8000 == 0
+}
+
+func (pf PacketFlags) DontFrag() bool {
+	return pf&0x4000 == 0x4000
+}
+
+func (pf PacketFlags) NoFrag() bool {
+	return pf == 0x4000
+}
+
+func (pf PacketFlags) IsSingle() bool {
+	return pf == 0
+}
+
+func (pf PacketFlags) ZeroOffset() bool {
+	return pf&0x1fff == 0
+}
+
+func (pf PacketFlags) Offset() uint16 {
+	return uint16(pf << 3)
+}
+
+// Flags extract flags from raw data
+func Flags(data []byte) PacketFlags {
+	return PacketFlags(binary.LittleEndian.Uint16(data[10:12]))
+}
diff --git a/gold/head/packet.go b/gold/head/packet.go
index e5509f0..ca4975d 100644
--- a/gold/head/packet.go
+++ b/gold/head/packet.go
@@ -4,7 +4,6 @@ import (
 	"encoding/binary"
 	"encoding/hex"
 	"errors"
-	"hash/crc64"
 	"net"
 
 	blake2b "github.com/fumiama/blake2b-simd"
@@ -21,37 +20,6 @@ var (
 	ErrDataLenLT60    = errors.New("data len < 60")
 )
 
-type PacketFlags uint16
-
-func (pf PacketFlags) IsValid() bool {
-	return pf&0x8000 == 0
-}
-
-func (pf PacketFlags) DontFrag() bool {
-	return pf&0x4000 == 0x4000
-}
-
-func (pf PacketFlags) NoFrag() bool {
-	return pf == 0x4000
-}
-
-func (pf PacketFlags) IsSingle() bool {
-	return pf == 0
-}
-
-func (pf PacketFlags) ZeroOffset() bool {
-	return pf&0x1fff == 0
-}
-
-func (pf PacketFlags) Offset() uint16 {
-	return uint16(pf << 3)
-}
-
-// Flags extract flags from raw data
-func Flags(data []byte) PacketFlags {
-	return PacketFlags(binary.LittleEndian.Uint16(data[10:12]))
-}
-
 // Packet 是发送和接收的最小单位
 type Packet struct {
 	// idxdatsz len(Data)
@@ -77,7 +45,7 @@ type Packet struct {
 	// 生成时 Hash 全 0
 	// https://github.com/fumiama/blake2b-simd
 	Hash [32]byte
-	// crc64 包头字段的 checksum 值，可以认为在一定时间内唯一
+	// crc64 包头字段的 checksum 值，可以认为在一定时间内唯一 (现已更改算法为 md5 但名字未变)
 	crc64 uint64
 	// data 承载的数据
 	data []byte
@@ -108,8 +76,8 @@ func (p *Packet) Unmarshal(data []byte) (complete bool, err error) {
 		err = ErrDataLenLT60
 		return
 	}
-	p.crc64 = binary.LittleEndian.Uint64(data[52:PacketHeadLen])
-	if crc64.Checksum(data[:52], crc64.MakeTable(crc64.ISO)) != p.crc64 {
+	p.crc64 = CRC64(data)
+	if CalcCRC64(data) != p.crc64 {
 		err = ErrBadCRCChecksum
 		return
 	}
@@ -189,7 +157,7 @@ func (p *Packet) Marshal(src net.IP, teatype uint8, additional uint16, datasz ui
 		w.Write(p.Src.To4())
 		w.Write(p.Dst.To4())
 		w.Write(p.Hash[:])
-		w.WriteUInt64(crc64.Checksum(w.Bytes(), crc64.MakeTable(crc64.ISO)))
+		w.WriteUInt64(CalcCRC64(w.Bytes()))
 		w.Write(p.Body())
 	})
 }
diff --git a/gold/head/raw.go b/gold/head/raw.go
new file mode 100644
index 0000000..646873b
--- /dev/null
+++ b/gold/head/raw.go
@@ -0,0 +1,22 @@
+package head
+
+import (
+	"crypto/md5"
+	"encoding/binary"
+)
+
+// CRC64 extract packet header checksum
+func CRC64(data []byte) uint64 {
+	return binary.LittleEndian.Uint64(data[52:PacketHeadLen])
+}
+
+// CalcCRC64 calculate packet header checksum
+func CalcCRC64(data []byte) uint64 {
+	m := md5.Sum(data[:52])
+	return binary.LittleEndian.Uint64(m[:8])
+}
+
+// Hash extract 32 bytes blake2b hash from raw bytes
+func Hash(data []byte) []byte {
+	return data[20:52]
+}
diff --git a/gold/link/recv.go b/gold/link/recv.go
index 2d71fbd..8f46196 100644
--- a/gold/link/recv.go
+++ b/gold/link/recv.go
@@ -40,7 +40,7 @@ func (m *Me) wait(data []byte) *head.Packet {
 		}
 		return nil
 	}
-	crc := binary.LittleEndian.Uint64(data[52:head.PacketHeadLen])
+	crc := head.CRC64(data)
 	crclog := crc
 	crc ^= (uint64(seq) << 16)
 	if config.ShowDebugLog {
@@ -67,7 +67,7 @@ func (m *Me) wait(data []byte) *head.Packet {
 	}
 
 	crchash := crc64.New(crc64.MakeTable(crc64.ISO))
-	_, _ = crchash.Write(data[20:52])
+	_, _ = crchash.Write(head.Hash(data))
 	var buf [4]byte
 	binary.LittleEndian.PutUint32(buf[:], seq)
 	_, _ = crchash.Write(buf[:])