diff --git a/README.md b/README.md
new file mode 100644
index 0000000..66fba38
--- /dev/null
+++ b/README.md
@@ -0,0 +1,16 @@
+# Rigol HDO-series license generator
+
+* Obtain the IP address of the scope
+* Connect to the scope using the Android Debug Bridge `adb connect <IP of scope>:55555`
+* Download the unique key from the scope `adb pull /rigol/data/Key.data`
+* Generate the license key using the rgtool program on the Key file `go run ./rgtool.go`
+* Insert generated codes via SCPI interface on the website on the scope (`http://<IP of scope>`)
+
+When not wanting to install adb or go, docker could also be used instead.
+```sh
+docker run --rm -it -v $(pwd):/workdir -w /workdir alpine \
+  /bin/sh -c 'apk add android-tools && adb connect <IP of scope>:55555 && adb pull /rigol/data/Key.data'
+```
+```sh
+docker run --rm -it -v $(pwd):/workdir -w /workdir golang go run ./rgtool.go
+```
diff --git a/rgtool.go b/rgtool.go
new file mode 100644
index 0000000..cb7a530
--- /dev/null
+++ b/rgtool.go
@@ -0,0 +1,227 @@
+package main
+
+import (
+	"bytes"
+	"crypto/aes"
+	"encoding/binary"
+	"errors"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os/user"
+	"path/filepath"
+)
+
+/*
+0 maybe device ID, not needed to work
+1
+2 lic name string
+3 lic Type "0"
+4 lic time "0"
+5
+*/
+
+var keyFile string
+var deviceId string
+
+func initCmdline() {
+	flag.StringVar(&keyFile, "k", "Key.data", "key file")
+	flag.StringVar(&deviceId, "id", "HDO4XXXXXX", "devide Id")
+	flag.Parse()
+}
+
+func Expand(path string) string {
+	if len(path) == 0 || path[0] != '~' {
+		return path
+	}
+	usr, err := user.Current()
+	if err != nil {
+		return path
+	}
+	return filepath.Join(usr.HomeDir, path[1:])
+}
+
+const delta = 0x9E3779B9
+
+func mx(sum uint32, y uint32, z uint32, p uint32, e uint32, k []uint32) uint32 {
+	return ((z>>5 ^ y<<2) + (y>>3 ^ z<<4)) ^ ((sum ^ y) + (k[p&3^e] ^ z))
+}
+
+func fixk(k []uint32) []uint32 {
+	if len(k) < 4 {
+		key := make([]uint32, 4)
+		copy(key, k)
+		return key
+	}
+	return k
+}
+
+func XXTeaEncrypt(v []uint32, k []uint32) []uint32 {
+	length := uint32(len(v))
+	n := length - 1
+	k = fixk(k)
+	var y, z, sum, e, p, q uint32
+	z = v[n]
+	sum = 0
+	for q = 6 + 52/length; q > 0; q-- {
+		sum += delta
+		e = sum >> 2 & 3
+		for p = 0; p < n; p++ {
+			y = v[p+1]
+			v[p] += mx(sum, y, z, p, e, k)
+			z = v[p]
+		}
+		y = v[0]
+		v[n] += mx(sum, y, z, p, e, k)
+		z = v[n]
+	}
+	return v
+}
+
+func XXTeaDecrypt(v []uint32, k []uint32) []uint32 {
+	length := uint32(len(v))
+	n := length - 1
+	k = fixk(k)
+	var y, z, sum, e, p, q uint32
+	y = v[0]
+	q = 6 + 52/length
+	for sum = q * delta; sum != 0; sum -= delta {
+		e = sum >> 2 & 3
+		for p = n; p > 0; p-- {
+			z = v[p-1]
+			v[p] -= mx(sum, y, z, p, e, k)
+			y = v[p]
+		}
+		z = v[n]
+		v[0] -= mx(sum, y, z, p, e, k)
+		y = v[0]
+	}
+	return v
+}
+
+func HexString(data []byte) string {
+	var buf bytes.Buffer
+	for i := 0; i < len(data)-1; i++ {
+		buf.WriteString(fmt.Sprintf("%02X ", data[i]))
+	}
+	buf.WriteString(fmt.Sprintf("%02X", data[len(data)-1]))
+	return buf.String()
+}
+
+func HexStringS(data []byte, sep string) string {
+	var buf bytes.Buffer
+	for i := 0; i < len(data)-1; i++ {
+		buf.WriteString(fmt.Sprintf("%02X%s", data[i], sep))
+	}
+	buf.WriteString(fmt.Sprintf("%02X", data[len(data)-1]))
+	return buf.String()
+}
+
+func HexStringLsb(data []byte, sep string) string {
+	var buf bytes.Buffer
+	for i := 0; i < len(data)-1; i++ {
+		buf.WriteString(fmt.Sprintf("%02x%s", (data[i]<<4)|(data[i]>>4), sep))
+	}
+	t := data[len(data)-1]
+	buf.WriteString(fmt.Sprintf("%02x", (t<<4)|(t>>4)))
+	return buf.String()
+}
+
+func decodeDefaultXXTEA(data []byte) []byte {
+	k := []uint32{0x03920001, 0x08410841, 0x18C32104, 0x318639C7}
+	N := len(data)
+	u32 := make([]uint32, N>>2)
+	for i, _ := range u32 {
+		u32[i] = binary.LittleEndian.Uint32(data[i*4:])
+	}
+	u32d := XXTeaDecrypt(u32, k)
+	res := make([]uint8, N)
+	for i, v := range u32d {
+		binary.LittleEndian.PutUint32(res[i*4:], v)
+	}
+	return res
+}
+
+func EncryptLicenseString(key []uint8, str string) (string, error) {
+	block, err := aes.NewCipher(key)
+	if nil != err {
+		return "", err
+	}
+	x := make([]uint8, 48)
+	copy(x, []uint8(str))
+	block.Encrypt(x, x)
+	block.Encrypt(x[0x10:], x[0x10:])
+	block.Encrypt(x[0x20:], x[0x20:])
+	return HexStringLsb(x, ""), nil
+}
+
+func MakeLicense(key []uint8, deviceId, feature string) string {
+	s := fmt.Sprintf("%s#0#%s#4#0#0", deviceId, feature)
+	res, err := EncryptLicenseString(key, s)
+	if nil != err {
+		return ""
+	}
+	return fmt.Sprintf("HDO4000-%s@%s", feature, res)
+}
+
+func LoadKeys() ([]uint8, error) {
+	data, err := ioutil.ReadFile(Expand(keyFile))
+	if nil != err {
+		return nil, err
+	}
+	dd := decodeDefaultXXTEA(data)
+	i := bytes.Index(dd, []uint8(";"))
+	if -1 == i {
+		return nil, errors.New("key format error")
+	}
+	fmt.Printf("Key: %v\n", string(dd))
+	return dd[i+1:], nil
+
+}
+
+// BND
+// MSO
+// COMP
+// EMBD
+// AUTO
+// FLEX
+// AUDIO
+// AERO
+// ARINC
+// DG
+// JITTER
+// EYE
+// RTSA
+// CM_USB
+// CM_ENET
+// CM_IPI
+// CM_HDMI
+// PWR
+// UPA
+// RLU
+// BODE
+// BW7T10
+// BW7T20
+// BW100T20
+// BW2T4
+// BW2T8
+// BW4T8
+// COUNT
+// UNKNOWN
+
+var options []string = []string{"EMBD", "AUTO", "BW2T8", "COMP", "AERO", "FLEX", "AUDIO", "RLU", "UPA"}
+
+func main() {
+	initCmdline()
+	k, err := LoadKeys()
+	if nil != err {
+		fmt.Printf("error %v\n", err)
+		return
+	}
+	fmt.Printf("Generating options for %s\n", deviceId)
+	for _, o := range options {
+		lic := MakeLicense(k[0:32], deviceId, o)
+		fmt.Printf(":SYST:OPT:INST %v\n", lic)
+	}
+
+}