diff --git a/backend/src/confirmation.rs b/backend/src/confirmation.rs
index 6617dba..08d52e7 100644
--- a/backend/src/confirmation.rs
+++ b/backend/src/confirmation.rs
@@ -6,7 +6,7 @@ use crate::errors::SpecialErrors;
 use crate::management::{delete_key, Action, Pending};
 use crate::settings::{MAILER, SETTINGS};
 use crate::utils::{get_email_from_cert, insert_key, parse_pem, read_file};
-use crate::{log_err, pending_path};
+use crate::{log_err, pending_path, validate_cert};
 use anyhow::Result;
 
 use lettre::{AsyncTransport, Message};
@@ -25,8 +25,9 @@ pub fn confirm_action(token: &str) -> Result<(Action, String)> {
         let address = match key.action() {
             Action::Add => {
                 let cert = parse_pem(key.data())?;
-                let email = get_email_from_cert(&cert)?;
-                log_err!(insert_key(&cert), warn)?;
+                let validcert = validate_cert!(cert)?;
+                let email = get_email_from_cert(&validcert)?;
+                log_err!(insert_key(&validcert), warn)?;
                 email
             }
             Action::Delete => {
diff --git a/backend/src/errors.rs b/backend/src/errors.rs
index 903c5d9..fde8436 100644
--- a/backend/src/errors.rs
+++ b/backend/src/errors.rs
@@ -36,6 +36,8 @@ macro_rules! log_err {
 
 #[derive(Debug, DeriveError)]
 pub enum SpecialErrors {
+    #[error("Uploaded certificate contains a secret key!")]
+    ContainsSecret,
     #[error("Could not find any primay user email in the keyblock!")]
     EmailMissing,
     #[error("The request had expired!")]
@@ -92,6 +94,7 @@ impl ResponseError for CompatErr {
         match self {
             Self::AnyhowErr(_) => StatusCode::INTERNAL_SERVER_ERROR,
             Self::SpecialErr(error) => match error {
+                SpecialErrors::ContainsSecret => StatusCode::BAD_REQUEST,
                 SpecialErrors::ExpiredRequest => StatusCode::BAD_REQUEST,
                 SpecialErrors::InexistingUser => StatusCode::NOT_FOUND,
                 SpecialErrors::InvalidCert => StatusCode::BAD_REQUEST,
diff --git a/backend/src/main.rs b/backend/src/main.rs
index 255d1f3..c201749 100644
--- a/backend/src/main.rs
+++ b/backend/src/main.rs
@@ -101,7 +101,11 @@ async fn index(req: HttpRequest) -> Result<HttpResponse, CompatErr> {
 #[post("/api/submit")]
 async fn submit(pem: web::Form<Key>) -> Result<HttpResponse, CompatErr> {
     let cert = parse_pem(&pem.key)?;
-    let email = get_email_from_cert(&cert)?;
+    let validcert = validate_cert!(cert)?;
+    if validcert.is_tsk() {
+        Err(SpecialErrors::ContainsSecret)?
+    }
+    let email = get_email_from_cert(&validcert)?;
     debug!("Handling user {} request to add a key...", email);
     is_email_allowed(&email)?;
     let token = gen_random_token();
diff --git a/backend/src/utils.rs b/backend/src/utils.rs
index b4a9f80..05d8fa6 100644
--- a/backend/src/utils.rs
+++ b/backend/src/utils.rs
@@ -15,6 +15,7 @@ use flexi_logger::{style, DeferredNow, FileSpec, FlexiLoggerError, Logger, Logge
 use log::debug;
 use log::error;
 use rand::{distributions::Alphanumeric, thread_rng, Rng};
+use sequoia_openpgp::cert::ValidCert;
 use sequoia_openpgp::serialize::Marshal;
 use sequoia_openpgp::types::HashAlgorithm;
 use sequoia_openpgp::{parse::Parse, Cert};
@@ -59,13 +60,12 @@ pub fn email_to_file_path(email: &str) -> Result<PathBuf> {
     Ok(PathBuf::from(ROOT_FOLDER).join(directory))
 }
 
-pub fn insert_key(cert: &Cert) -> Result<()> {
-    let validcert = validate_cert!(cert)?;
+pub fn insert_key(cert: &ValidCert) -> Result<()> {
     let path = email_to_file_path(&get_email_from_cert(cert)?)?;
 
     fs::create_dir_all(path.parent().unwrap())?;
     let mut file = fs::File::create(&path)?;
-    validcert.export(&mut file)?;
+    cert.export(&mut file)?;
 
     fs::OpenOptions::new()
         .write(true)
@@ -115,9 +115,8 @@ pub fn gen_random_token() -> String {
     (0..10).map(|_| rng.sample(Alphanumeric) as char).collect()
 }
 
-pub fn get_email_from_cert(cert: &Cert) -> Result<String> {
-    let validcert = validate_cert!(cert)?;
-    let userid_opt = log_err!(validcert.primary_userid(), debug)?;
+pub fn get_email_from_cert(cert: &ValidCert) -> Result<String> {
+    let userid_opt = log_err!(cert.primary_userid(), debug)?;
     let email_opt = userid_opt.email()?;
     match email_opt {
         Some(email) => Ok(email),