encoding message to and from string works with verification.

config.go

 package main
 
 import (
+	"encoding/base64"
 	"encoding/json"
 	"io/ioutil"
 	"log"
 	}
 	return json.Unmarshal(body, &APIConfig)
 }
+
+//convert AesEncryptKey into Binary 32bytes
+func getAesEncryptKey() [32]byte {
+	key, _ := base64.StdEncoding.DecodeString(APIConfig.EncodingAESKey + "=")
+	var k [32]byte
+	copy(k[:], key)
+	return k
+}

main.go

 		return
 	}
 
-	Decode("SS")
+	const txt = "P2DoRtilYwJ1aM+VW1sGs6p11Rhcd/TrFYtvsw53SUVw2Knh27hF5IZUBxRXbz+k87zy983ec5aOwgS+WxYoejmGubaqiYy2yfCBNyGRlWfe+iWc2TnvPIEAJebSWuNOJ7FoITeMndr4tW391XxDdMom8I/VsqKnsZZAangUsxmA1ZEnP/d4Lx8/xt3qJKrJMa4Q8s9VsOOvzLIGhL1IN5bHaXN+CwgBTAUCrHD8AneiX5MLSv/74qozg+jKBSUebZrjRYuTymQ3TBh3pQXyRBQTZNrCAe1tlcNli9e5MSUMsHFIzGw/kiu93/5VkxCYRLgRDQKl9oam4+Rpxywir7EiT7I4X343l9ogcMLWX16evkLlQHoqBhLl6ZcfW7Nmq8/Ghy8jbuwqkR/0jLJ/avtjzgJOwaxdBUz4nYZ452rLJekxIvsmV6PZgCXRrKHzmpZX+i6hIRIWiIaDeMOEsw=="
+	const msg = `<xml><ToUserName><![CDATA[gh_f09231355c68]]></ToUserName>
+<FromUserName><![CDATA[oUN420bxqFqlx0ZQHciUOesZO3PE]]></FromUserName>
+<CreateTime>1492972518</CreateTime>
+<MsgType><![CDATA[event]]></MsgType>
+<Event><![CDATA[CLICK]]></Event>
+<EventKey><![CDATA[V1001_TODAY_MUSIC]]></EventKey>
+</xml>`
+	m := Decode(txt)
+	t := Encode(msg)
+	fmt.Println(t)
+	fmt.Println(m)
+	fmt.Println(t == txt)
+	fmt.Println(m == msg)
+
 	return
 	//setup handler
 	http.HandleFunc("/", webrootHandler)

messageEncrypt.go

 import (
 	"crypto/aes"
 	"crypto/cipher"
+	"crypto/rand"
 	"encoding/base64"
 	"fmt"
 )
 
-const txt = "P2DoRtilYwJ1aM+VW1sGs6p11Rhcd/TrFYtvsw53SUVw2Knh27hF5IZUBxRXbz+k87zy983ec5aOwgS+WxYoejmGubaqiYy2yfCBNyGRlWfe+iWc2TnvPIEAJebSWuNOJ7FoITeMndr4tW391XxDdMom8I/VsqKnsZZAangUsxmA1ZEnP/d4Lx8/xt3qJKrJMa4Q8s9VsOOvzLIGhL1IN5bHaXN+CwgBTAUCrHD8AneiX5MLSv/74qozg+jKBSUebZrjRYuTymQ3TBh3pQXyRBQTZNrCAe1tlcNli9e5MSUMsHFIzGw/kiu93/5VkxCYRLgRDQKl9oam4+Rpxywir7EiT7I4X343l9ogcMLWX16evkLlQHoqBhLl6ZcfW7Nmq8/Ghy8jbuwqkR/0jLJ/avtjzgJOwaxdBUz4nYZ452rLJekxIvsmV6PZgCXRrKHzmpZX+i6hIRIWiIaDeMOEsw=="
+var random16 []byte
 
-//Decode  Decode encrypt string to xml context
-func Decode(s string) string {
+//Encode convert a xml sequence into encrypted message
+func Encode(s string) string {
 
-	r, _ := base64.StdEncoding.DecodeString(txt)
+	d := aesEncryptMsg(random16, []byte(s), APIConfig.Appid, getAesEncryptKey())
+	r := base64.StdEncoding.EncodeToString(d)
+	fmt.Println(r)
+	return r
+}
 
-	key, _ := base64.StdEncoding.DecodeString(APIConfig.EncodingAESKey + "=")
-	var k [32]byte
-	copy(k[:], key)
-	random, raw, err := AESDecryptMsg([]byte(r), APIConfig.Appid, k)
+//Decode  Decode encrypt string to xml context
+func Decode(s string) string {
 
-	fmt.Println(len(txt))
-	fmt.Println(random)
-	fmt.Println(string(raw))
+	r, _ := base64.StdEncoding.DecodeString(s)
 
-	bc, err := aes.NewCipher([]byte(key))
+	r16, raw, err := aesDecryptMsg([]byte(r), APIConfig.Appid, getAesEncryptKey())
+	random16 = make([]byte, 16)
+	copy(random16, r16)
 	if err == nil {
-		fmt.Printf("The block size is %d\n", bc.BlockSize())
-		var decoded = make([]byte, 4096)
-		bc.Decrypt(decoded, r)
-		//AES Decode
+		fmt.Println(string(raw))
+		return string(raw)
 	}
-	fmt.Printf("%s", string(r))
-	return string(r)
+	return ""
 }
 
 // 把整数 n 格式化成 4 字节的网络字节序
 	return
 }
 
-//AESEncryptMsg encryptedMsg = AES_Encrypt[random(16B) + msg_len(4B) + rawXMLMsg + AppId]
-func AESEncryptMsg(random, rawXMLMsg []byte, AppId string, AESKey [32]byte) (encryptedMsg []byte) {
+func random16Byte() []byte {
+	token := make([]byte, 16)
+	rand.Read(token)
+	return token
+}
+
+//AESEncryptMsg given an xml message and 16 bytes random string
+//encryptedMsg = AES_Encrypt[random(16B) + msg_len(4B) + rawXMLMsg + AppId]
+func aesEncryptMsg(random, rawXMLMsg []byte, AppId string, AESKey [32]byte) (encryptedMsg []byte) {
 	const BLOCK_SIZE = 32 // PKCS#7
 
 	buf := make([]byte, 20+len(rawXMLMsg)+len(AppId)+BLOCK_SIZE)
 	return
 }
 
+//AESDecryptMsg  given a string decode it into three parts
 // encryptedMsg = AES_Encrypt[random(16B) + msg_len(4B) + rawXMLMsg + AppId]
-func AESDecryptMsg(encryptedMsg []byte, AppId string, AESKey [32]byte) (random, rawXMLMsg []byte, err error) {
+func aesDecryptMsg(encryptedMsg []byte, AppId string, AESKey [32]byte) (random, rawXMLMsg []byte, err error) {
 	const BLOCK_SIZE = 32 // PKCS#7
 
 	if len(encryptedMsg) < BLOCK_SIZE {