Added folder for german translation

de/code/src/apps/ch.4.5/nonce/main.go

@@ -0,0 +1,70 @@
+// A nonce is a number or string used only once.
+// This is useful for generating a unique token for login pages to prevent duplicate submissions.
+package nonce
+
+import (
+	"crypto/md5"
+	"errors"
+	"fmt"
+	"io"
+	"math/rand"
+	"strconv"
+	"time"
+)
+
+// Contains a unique token
+type Nonce struct {
+	Token string
+}
+
+// Keeps track of marked/used tokens
+type Nonces struct {
+	hashs map[string]bool
+}
+
+func New() Nonces {
+	return Nonces{make(map[string]bool)}
+}
+func (n *Nonces) NewNonce() Nonce {
+	return Nonce{n.NewToken()}
+}
+
+// Returns a new unique token
+func (n *Nonces) NewToken() string {
+	t := createToken()
+	for n.HasToken(t) {
+		t = createToken()
+	}
+	return t
+}
+
+// Checks if token has been marked.
+func (n *Nonces) HasToken(token string) bool {
+	return n.hashs[token] == true
+}
+func (n *Nonces) MarkToken(token string) {
+	n.hashs[token] = true
+}
+func (n *Nonces) CheckToken(token string) error {
+	if token == "" {
+		return errors.New("No token supplied")
+	}
+	if n.HasToken(token) {
+		return errors.New("Duplicate submission.")
+	}
+	return nil
+}
+func (n *Nonces) CheckThenMarkToken(token string) error {
+	defer n.MarkToken(token)
+	if err := n.CheckToken(token); err != nil {
+		return err
+	}
+	return nil
+}
+func createToken() string {
+	h := md5.New()
+	now := time.Now().Unix()
+	io.WriteString(h, strconv.FormatInt(now, 10))
+	io.WriteString(h, strconv.FormatInt(rand.Int63(), 10))
+	return fmt.Sprintf("%x", h.Sum(nil))
+}