finish OTP code

crypto.go

@@ -5,21 +5,36 @@ import (
 	"crypto/sha1"
 	"crypto/sha256"
 	"encoding/base32"
+	"encoding/base64"
 	"encoding/binary"
 	"errors"
 	"fmt"
 	"hash"
 	"math"
+	"math/rand"
 	"strings"
 	"time"
 )
 
+func NewSalt() string {
+	var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+	b := make([]rune, 4)
+	for i := range b {
+		b[i] = letterRunes[rand.Intn(len(letterRunes))]
+	}
+	return string(b)
+}
+
 func ComputeHmac256(message string, secret string) []byte {
 	h := hmac.New(sha256.New, []byte(secret))
 	h.Write([]byte(message))
 	return h.Sum(nil)
 }
 
+func encode64(secret []byte) string {
+	return strings.TrimRight(base64.StdEncoding.EncodeToString(secret), "=")
+}
+
 func encodeSecret(secret []byte) string {
 	return strings.TrimRight(base32.StdEncoding.EncodeToString(secret), "=")
 }