import (
 "fmt"
 "crypto/md5"
 "encoding/base64"
 "time"
)

var cipher = "密鑰"
var h = md5.New()

func cipherEncode(sourceText string) string { 
 h.Write([]byte(cipher))
 cipherHash := fmt.Sprintf("%x", h.Sum(nil))
 h.Reset()
 inputData := []byte(sourceText)
 loopCount := len(inputData)
 outData := make([]byte,loopCount)
 for i:= 0; i < loopCount ; i++ {
  outData[i] = inputData[i] ^ cipherHash[i%32]
 } 
 return fmt.Sprintf("%s", outData)
}

func encode(sourceText string) string { 
 h.Write([]byte(time.Now().Format("2006-01-02 15:04:05")))
 noise := fmt.Sprintf("%x", h.Sum(nil))
 h.Reset()
 inputData := []byte(sourceText)
 loopCount := len(inputData)
 outData := make([]byte,loopCount*2)
 
 for i, j := 0,0; i < loopCount ; i,j = i+1,j+1 {  
  outData[j] = noise[i%32]
  j++
  outData[j] = inputData[i] ^ noise[i%32]
 }
 
 return base64.StdEncoding.EncodeToString([]byte(cipherEncode(fmt.Sprintf("%s", outData))))
}

func decode(sourceText string) string {
 buf, err := base64.StdEncoding.DecodeString(sourceText)
 if err != nil {
  fmt.Println("Decode(%q) failed: %v", sourceText, err)
  return ""
 }
 inputData := []byte(cipherEncode(fmt.Sprintf("%s", buf)))
 loopCount := len(inputData)
 outData := make([]byte,loopCount)
 for i, j := 0,0; i < loopCount ; i,j = i+2,j+1 {  
  outData[j] = inputData[i] ^ inputData[i+1]
 }
 return fmt.Sprintf("%s", outData)
}

func main() {
        s := encode("張學友")
 fmt.Println(s)
 fmt.Println(decode(s))
}