diff --git a/lib/protocol/deviceid.go b/lib/protocol/deviceid.go
index 2e412461..df1cbdec 100644
--- a/lib/protocol/deviceid.go
+++ b/lib/protocol/deviceid.go
@@ -8,7 +8,6 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
-	"regexp"
 	"strings"
 
 	"github.com/calmh/luhn"
@@ -155,16 +154,17 @@ func luhnify(s string) (string, error) {
 		panic("unsupported string length")
 	}
 
-	res := make([]string, 0, 4)
+	res := make([]byte, 4*(13+1))
 	for i := 0; i < 4; i++ {
 		p := s[i*13 : (i+1)*13]
+		copy(res[i*(13+1):], p)
 		l, err := luhn.Base32.Generate(p)
 		if err != nil {
 			return "", err
 		}
-		res = append(res, fmt.Sprintf("%s%c", p, l))
+		res[(i+1)*(13)+i] = byte(l)
 	}
-	return res[0] + res[1] + res[2] + res[3], nil
+	return string(res), nil
 }
 
 func unluhnify(s string) (string, error) {
@@ -172,25 +172,31 @@ func unluhnify(s string) (string, error) {
 		return "", fmt.Errorf("%q: unsupported string length %d", s, len(s))
 	}
 
-	res := make([]string, 0, 4)
+	res := make([]byte, 52)
 	for i := 0; i < 4; i++ {
-		p := s[i*14 : (i+1)*14-1]
+		p := s[i*(13+1) : (i+1)*(13+1)-1]
+		copy(res[i*13:], p)
 		l, err := luhn.Base32.Generate(p)
 		if err != nil {
 			return "", err
 		}
-		if g := fmt.Sprintf("%s%c", p, l); g != s[i*14:(i+1)*14] {
+		if s[(i+1)*14-1] != byte(l) {
 			return "", fmt.Errorf("%q: check digit incorrect", s)
 		}
-		res = append(res, p)
 	}
-	return res[0] + res[1] + res[2] + res[3], nil
+	return string(res), nil
 }
 
 func chunkify(s string) string {
-	s = regexp.MustCompile("(.{7})").ReplaceAllString(s, "$1-")
-	s = strings.Trim(s, "-")
-	return s
+	chunks := len(s) / 7
+	res := make([]byte, chunks*(7+1)-1)
+	for i := 0; i < chunks; i++ {
+		if i > 0 {
+			res[i*(7+1)-1] = '-'
+		}
+		copy(res[i*(7+1):], s[i*7:(i+1)*7])
+	}
+	return string(res)
 }
 
 func unchunkify(s string) string {
diff --git a/lib/protocol/deviceid_test.go b/lib/protocol/deviceid_test.go
index 02893b2a..0f9e3527 100644
--- a/lib/protocol/deviceid_test.go
+++ b/lib/protocol/deviceid_test.go
@@ -150,3 +150,41 @@ func TestNewDeviceIDMarshalling(t *testing.T) {
 		t.Error("Mismatch in old -> new direction")
 	}
 }
+
+var resStr string
+
+func BenchmarkLuhnify(b *testing.B) {
+	str := "ABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJAB"
+	var err error
+	for i := 0; i < b.N; i++ {
+		resStr, err = luhnify(str)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkUnluhnify(b *testing.B) {
+	str, _ := luhnify("ABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJAB")
+	var err error
+	for i := 0; i < b.N; i++ {
+		resStr, err = unluhnify(str)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkChunkify(b *testing.B) {
+	str := "ABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJAB"
+	for i := 0; i < b.N; i++ {
+		resStr = chunkify(str)
+	}
+}
+
+func BenchmarkUnchunkify(b *testing.B) {
+	str := chunkify("ABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJAB")
+	for i := 0; i < b.N; i++ {
+		resStr = unchunkify(str)
+	}
+}
diff --git a/vendor/github.com/calmh/luhn/luhn.go b/vendor/github.com/calmh/luhn/luhn.go
index 8bcb0cd1..f09f3f29 100644
--- a/vendor/github.com/calmh/luhn/luhn.go
+++ b/vendor/github.com/calmh/luhn/luhn.go
@@ -19,10 +19,6 @@ var (
 // Generate returns a check digit for the string s, which should be composed
 // of characters from the Alphabet a.
 func (a Alphabet) Generate(s string) (rune, error) {
-	if err := a.check(); err != nil {
-		return 0, err
-	}
-
 	factor := 1
 	sum := 0
 	n := len(a)
@@ -57,14 +53,15 @@ func (a Alphabet) Validate(s string) bool {
 	return rune(s[len(s)-1]) == c
 }
 
-// check returns an error if the given alphabet does not consist of unique characters
-func (a Alphabet) check() error {
-	cm := make(map[byte]bool, len(a))
-	for i := range a {
-		if cm[a[i]] {
-			return fmt.Errorf("Digit %q non-unique in alphabet %q", a[i], a)
+// NewAlphabet converts the given string an an Alphabet, verifying that it
+// is correct.
+func NewAlphabet(s string) (Alphabet, error) {
+	cm := make(map[byte]bool, len(s))
+	for i := range s {
+		if cm[s[i]] {
+			return "", fmt.Errorf("Digit %q non-unique in alphabet %q", s[i], s)
 		}
-		cm[a[i]] = true
+		cm[s[i]] = true
 	}
-	return nil
+	return Alphabet(s), nil
 }
diff --git a/vendor/manifest b/vendor/manifest
index a6080cd2..72d9c1c0 100644
--- a/vendor/manifest
+++ b/vendor/manifest
@@ -53,7 +53,7 @@
 			"importpath": "github.com/calmh/luhn",
 			"repository": "https://github.com/calmh/luhn",
 			"vcs": "git",
-			"revision": "0c8388ff95fa92d4094011e5a04fc99dea3d1632",
+			"revision": "c0f1d77264fb3d1bfc65b70eea6ee264058c57c0",
 			"branch": "master",
 			"notests": true
 		},