diff --git a/db/auth.go b/db/auth.go
index 793f8a6..1052969 100644
--- a/db/auth.go
+++ b/db/auth.go
@@ -38,19 +38,19 @@ func NewUser(id uuid.UUID, email string, emailVerified bool, emailVerifiedAt tim
 	}
 }
 
-type Auth interface {
+type DbAuth interface {
 	GetUser(email string) (*User, error)
 }
 
-type AuthSqlite struct {
+type DbAuthSqlite struct {
 	db *sql.DB
 }
 
-func NewAuthSqlite(db *sql.DB) *AuthSqlite {
-	return &AuthSqlite{db: db}
+func NewDbAuthSqlite(db *sql.DB) *DbAuthSqlite {
+	return &DbAuthSqlite{db: db}
 }
 
-func (a AuthSqlite) GetUser(email string) (*User, error) {
+func (db DbAuthSqlite) GetUser(email string) (*User, error) {
 	var (
 		userId          uuid.UUID
 		emailVerified   bool
@@ -61,7 +61,7 @@ func (a AuthSqlite) GetUser(email string) (*User, error) {
 		createdAt       time.Time
 	)
 
-	err := a.db.QueryRow(`
+	err := db.db.QueryRow(`
 		SELECT user_uuid, email_verified, email_verified_at, password, salt, created_at
 		FROM user 
 		WHERE email = ?`, email).Scan(&userId, &emailVerified, &emailVerifiedAt, &password, &salt, &createdAt)
diff --git a/db/auth_test.go b/db/auth_test.go
index 3dcaa45..3084f63 100644
--- a/db/auth_test.go
+++ b/db/auth_test.go
@@ -29,7 +29,7 @@ func TestGetUser(t *testing.T) {
 		db := setupDb(t)
 		defer db.Close()
 
-		underTest := AuthSqlite{db: db}
+		underTest := DbAuthSqlite{db: db}
 
 		_, err := underTest.GetUser("someNonExistentEmail")
 		if err != UserNotFound {
@@ -42,7 +42,7 @@ func TestGetUser(t *testing.T) {
 		db := setupDb(t)
 		defer db.Close()
 
-		underTest := AuthSqlite{db: db}
+		underTest := DbAuthSqlite{db: db}
 
 		verifiedAt := time.Date(2020, 1, 5, 13, 0, 0, 0, time.UTC)
 		createAt := time.Date(2020, 1, 5, 12, 0, 0, 0, time.UTC)
diff --git a/handler/auth.go b/handler/auth.go
index 5bb74f3..e8b3c69 100644
--- a/handler/auth.go
+++ b/handler/auth.go
@@ -1,61 +1,88 @@
 package handler
 
 import (
+	"me-fit/db"
 	"me-fit/service"
 	"me-fit/utils"
+	"time"
 
 	"database/sql"
 	"net/http"
 )
 
-type AuthHandler struct {
+type HandlerAuth interface {
+	handle(router *http.ServeMux)
+}
+
+type HandlerAuthImpl struct {
 	db      *sql.DB
-	service *service.AuthService
+	service service.ServiceAuth
 }
 
-func handleAuth(db *sql.DB, router *http.ServeMux) {
-	a := AuthHandler{
+func NewHandlerAuth(db *sql.DB, service service.ServiceAuth) HandlerAuth {
+	return HandlerAuthImpl{
 		db:      db,
-		service: service.NewAuthService(db),
+		service: service,
 	}
-	// Don't use auth middleware for these routes, as it makes redirecting very difficult, if the mail is not yet verified
-	router.Handle("/auth/signin", service.HandleSignInPage(db))
-	router.Handle("/auth/signup", service.HandleSignUpPage(db))
-	router.Handle("/auth/verify", service.HandleSignUpVerifyPage(db)) // Hint for the user to verify their email
-	router.Handle("/auth/delete-account", service.HandleDeleteAccountPage(db))
-	router.Handle("/auth/verify-email", service.HandleSignUpVerifyResponsePage(db)) // The link contained in the email
-	router.Handle("/auth/change-password", service.HandleChangePasswordPage(db))
-	router.Handle("/auth/reset-password", service.HandleResetPasswordPage(db))
-	router.Handle("/api/auth/signup", service.HandleSignUpComp(db))
-	router.Handle("/api/auth/signin", a.handleSignIn())
-	router.Handle("/api/auth/signout", service.HandleSignOutComp(db))
-	router.Handle("/api/auth/delete-account", service.HandleDeleteAccountComp(db))
-	router.Handle("/api/auth/verify-resend", service.HandleVerifyResendComp(db))
-	router.Handle("/api/auth/change-password", service.HandleChangePasswordComp(db))
-	router.Handle("/api/auth/reset-password", service.HandleResetPasswordComp(db))
-	router.Handle("/api/auth/reset-password-actual", service.HandleActualResetPasswordComp(db))
 }
 
-func (a AuthHandler) handleSignIn() http.HandlerFunc {
+func (handler HandlerAuthImpl) handle(router *http.ServeMux) {
+	// Don't use auth middleware for these routes, as it makes redirecting very difficult, if the mail is not yet verified
+	router.Handle("/auth/signin", service.HandleSignInPage(handler.db))
+	router.Handle("/auth/signup", service.HandleSignUpPage(handler.db))
+	router.Handle("/auth/verify", service.HandleSignUpVerifyPage(handler.db)) // Hint for the user to verify their email
+	router.Handle("/auth/delete-account", service.HandleDeleteAccountPage(handler.db))
+	router.Handle("/auth/verify-email", service.HandleSignUpVerifyResponsePage(handler.db)) // The link contained in the email
+	router.Handle("/auth/change-password", service.HandleChangePasswordPage(handler.db))
+	router.Handle("/auth/reset-password", service.HandleResetPasswordPage(handler.db))
+	router.Handle("/api/auth/signup", service.HandleSignUpComp(handler.db))
+	router.Handle("/api/auth/signin", handler.handleSignIn())
+	router.Handle("/api/auth/signout", service.HandleSignOutComp(handler.db))
+	router.Handle("/api/auth/delete-account", service.HandleDeleteAccountComp(handler.db))
+	router.Handle("/api/auth/verify-resend", service.HandleVerifyResendComp(handler.db))
+	router.Handle("/api/auth/change-password", service.HandleChangePasswordComp(handler.db))
+	router.Handle("/api/auth/reset-password", service.HandleResetPasswordComp(handler.db))
+	router.Handle("/api/auth/reset-password-actual", service.HandleActualResetPasswordComp(handler.db))
+}
+
+var (
+	securityWaitDuration = 250 * time.Millisecond
+)
+
+func (handler HandlerAuthImpl) handleSignIn() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		var email = r.FormValue("email")
-		var password = r.FormValue("password")
+		user, err := utils.WaitMinimumTime(securityWaitDuration, func() (*db.User, error) {
+			var email = r.FormValue("email")
+			var password = r.FormValue("password")
 
-		user := a.service.SignIn(email, password)
-
-		if user != nil {
-			result := service.TryCreateSessionAndSetCookie(r, w, a.db, user.Id)
-			if !result {
-				return
+			user, err := handler.service.SignIn(email, password)
+			if err != nil {
+				return nil, err
 			}
 
-			if !user.EmailVerified {
-				utils.DoRedirect(w, r, "/auth/verify")
+			err = service.TryCreateSessionAndSetCookie(r, w, handler.db, user.Id)
+			if err != nil {
+				return nil, err
+			}
+
+			return user, nil
+		})
+
+		if err != nil {
+			if err == service.InvaidEmailOrPassword {
+				utils.TriggerToast(w, r, "error", "Invalid email or password")
+				http.Error(w, "Invalid email or password", http.StatusUnauthorized)
 			} else {
-				utils.DoRedirect(w, r, "/")
+				utils.LogError("Error signing in", err)
+				http.Error(w, "An error occurred", http.StatusInternalServerError)
 			}
+			return
+		}
+
+		if user.EmailVerified {
+			utils.DoRedirect(w, r, "/")
 		} else {
-			http.Error(w, "Invalid email or password", http.StatusUnauthorized)
+			utils.DoRedirect(w, r, "/auth/verify")
 		}
 	}
 }
diff --git a/handler/default.go b/handler/default.go
index e877d59..34a1cf7 100644
--- a/handler/default.go
+++ b/handler/default.go
@@ -13,12 +13,14 @@ func GetHandler(db *sql.DB) http.Handler {
 
 	router.HandleFunc("/", service.HandleIndexAnd404(db))
 
+	handlerAuth := NewHandlerAuth(db, service.NewServiceAuthImpl(db))
+
 	// Serve static files (CSS, JS and images)
 	router.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.Dir("./static/"))))
 
 	handleWorkout(db, router)
 
-	handleAuth(db, router)
+	handlerAuth.handle(router)
 
 	return middleware.Logging(middleware.EnableCors(router))
 }
diff --git a/service/auth.go b/service/auth.go
index c03b4f8..4d805ee 100644
--- a/service/auth.go
+++ b/service/auth.go
@@ -11,7 +11,6 @@ import (
 	"net/mail"
 	"net/url"
 	"strings"
-	"time"
 
 	"me-fit/db"
 	"me-fit/template"
@@ -25,44 +24,42 @@ import (
 	"golang.org/x/crypto/argon2"
 )
 
-type AuthService struct {
-	db db.Auth
+var (
+	InvaidEmailOrPassword = errors.New("Invalid email or password")
+)
+
+type ServiceAuth interface {
+	SignIn(email string, password string) (*db.User, error)
 }
 
-func NewAuthService(d *sql.DB) *AuthService {
-	return &AuthService{
-		db: db.NewAuthSqlite(d),
+type ServiceAuthImpl struct {
+	dbAuth db.DbAuth
+}
+
+func NewServiceAuthImpl(d *sql.DB) *ServiceAuthImpl {
+	return &ServiceAuthImpl{
+		dbAuth: db.NewDbAuthSqlite(d),
 	}
 }
 
-func (a AuthService) SignIn(email string, password string) *db.User {
+func (service ServiceAuthImpl) SignIn(email string, password string) (*db.User, error) {
 
-	var result bool = true
-	start := time.Now()
-
-	user, err := a.db.GetUser(email)
+	user, err := service.dbAuth.GetUser(email)
 	if err != nil {
-		result = false
-	}
-
-	if result {
-		new_hash := getHashPassword(password, user.Salt)
-
-		if subtle.ConstantTimeCompare(new_hash, user.Password) == 0 {
-			result = false
+		if errors.Is(err, db.UserNotFound) {
+			return nil, InvaidEmailOrPassword
+		} else {
+			return nil, err
 		}
 	}
 
-	duration := time.Since(start)
-	timeToWait := 100 - duration.Milliseconds()
-	// It is important to sleep for a while to prevent timing attacks
-	// If the email is correct, the server will calculate the hash, which will take some time
-	// This way an attacker could guess emails when comparing the response time
-	// Because of that, we cant use WriteHeader in the middle of the function. We have to wait until the end
-	// Unfortunatly this makes the code harder to read
-	time.Sleep(time.Duration(timeToWait) * time.Millisecond)
+	hash := getHashPassword(password, user.Salt)
 
-	return user
+	if subtle.ConstantTimeCompare(hash, user.Password) == 0 {
+		return nil, InvaidEmailOrPassword
+	}
+
+	return user, nil
 }
 
 func HandleSignInPage(db *sql.DB) http.HandlerFunc {
@@ -286,8 +283,8 @@ func HandleSignUpComp(db *sql.DB) http.HandlerFunc {
 			return
 		}
 
-		result := TryCreateSessionAndSetCookie(r, w, db, userId)
-		if !result {
+		err = TryCreateSessionAndSetCookie(r, w, db, userId)
+		if err != nil {
 			return
 		}
 
@@ -603,25 +600,24 @@ func sendVerificationEmail(db *sql.DB, userId string, email string) {
 	utils.SendMail(email, "Welcome to ME-FIT", w.String())
 }
 
-func TryCreateSessionAndSetCookie(r *http.Request, w http.ResponseWriter, db *sql.DB, user_uuid uuid.UUID) bool {
+func TryCreateSessionAndSetCookie(r *http.Request, w http.ResponseWriter, db *sql.DB, user_uuid uuid.UUID) error {
 	sessionId, err := utils.RandomToken()
 	if err != nil {
 		utils.LogError("Could not generate session ID", err)
-		auth.Error("Internal Server Error").Render(r.Context(), w)
-		return false
+		return types.InternalServerError
 	}
 
 	// Delete old inactive sessions
 	_, err = db.Exec("DELETE FROM session WHERE created_at < datetime('now','-8 hours') AND user_uuid = ?", user_uuid)
 	if err != nil {
 		utils.LogError("Could not delete old sessions", err)
+		return types.InternalServerError
 	}
 
 	_, err = db.Exec("INSERT INTO session (session_id, user_uuid, created_at) VALUES (?, ?, datetime())", sessionId, user_uuid)
 	if err != nil {
 		utils.LogError("Could not insert session", err)
-		auth.Error("Internal Server Error").Render(r.Context(), w)
-		return false
+		return types.InternalServerError
 	}
 
 	cookie := http.Cookie{
@@ -635,7 +631,7 @@ func TryCreateSessionAndSetCookie(r *http.Request, w http.ResponseWriter, db *sq
 	}
 	http.SetCookie(w, &cookie)
 
-	return true
+	return nil
 }
 
 func getHashPassword(password string, salt []byte) []byte {
diff --git a/utils/http.go b/utils/http.go
index 406d0de..b6e29a4 100644
--- a/utils/http.go
+++ b/utils/http.go
@@ -90,6 +90,13 @@ func GetUserFromSession(db *sql.DB, r *http.Request) *types.User {
 
 }
 
+func WaitMinimumTime[T interface{}](waitTime time.Duration, function func() (T, error)) (T, error) {
+	start := time.Now()
+	result, err := function()
+	time.Sleep(waitTime - time.Since(start))
+	return result, err
+}
+
 func getSessionID(r *http.Request) string {
 	for _, c := range r.Cookies() {
 		if c.Name == "id" {