diff --git a/hooks/conf_regen/01-yunohost b/hooks/conf_regen/01-yunohost
index 45d0b58f6..e4bf2f0f2 100755
--- a/hooks/conf_regen/01-yunohost
+++ b/hooks/conf_regen/01-yunohost
@@ -60,12 +60,6 @@ do_init_regen() {
     chmod 700 /var/cache/yunohost
 
     getent passwd ynh-portal &>/dev/null || useradd --no-create-home --shell /usr/sbin/nologin --system --user-group ynh-portal
-    if [ ! -e /etc/yunohost/.ssowat_cookie_secret ]; then
-        # NB: we need this to be exactly 32 char long, because it is later used as a key for AES256
-        dd if=/dev/urandom bs=1 count=1000 2>/dev/null | tr --complement --delete 'A-Za-z0-9' | head -c 32 > /etc/yunohost/.ssowat_cookie_secret
-    fi
-    chown ynh-portal:root /etc/yunohost/.ssowat_cookie_secret
-    chmod 400 /etc/yunohost/.ssowat_cookie_secret
 
     # Portal folder
     mkdir -p /etc/yunohost/portal
@@ -81,6 +75,11 @@ do_init_regen() {
     chown ynh-portal:www-data /var/cache/yunohost-portal/sessions
     chmod 710 /var/cache/yunohost-portal/sessions
 
+    # Admin sessions
+    mkdir -p /var/cache/yunohost/sessions
+    chown root:root /var/cache/yunohost/sessions
+    chmod 700 /var/cache/yunohost/sessions
+
     # YunoHost services
     cp yunohost-api.service /etc/systemd/system/yunohost-api.service
     cp yunohost-portal-api.service /etc/systemd/system/yunohost-portal-api.service
@@ -201,6 +200,12 @@ EOF
 do_post_regen() {
     regen_conf_files=$1
 
+    if [ ! -e /etc/yunohost/.admin_cookie_secret ]; then
+        dd if=/dev/urandom bs=1 count=1000 2>/dev/null | tr --complement --delete 'A-Za-z0-9' | head -c 64 > /etc/yunohost/.admin_cookie_secret
+    fi
+    chown root:root /etc/yunohost/.admin_cookie_secret
+    chmod 400 /etc/yunohost/.admin_cookie_secret
+
     getent passwd ynh-portal &>/dev/null || useradd --no-create-home --shell /usr/sbin/nologin --system --user-group ynh-portal
     if [ ! -e /etc/yunohost/.ssowat_cookie_secret ]; then
         # NB: we need this to be exactly 32 char long, because it is later used as a key for AES256
@@ -272,6 +277,11 @@ do_post_regen() {
     chown ynh-portal:www-data /var/cache/yunohost-portal/sessions
     chmod 710 /var/cache/yunohost-portal/sessions
 
+    # Admin sessions
+    mkdir -p /var/cache/yunohost/sessions
+    chown root:root /var/cache/yunohost/sessions
+    chmod 700 /var/cache/yunohost/sessions
+
     # Domain settings
     mkdir -p /etc/yunohost/domains
 
diff --git a/src/authenticators/ldap_admin.py b/src/authenticators/ldap_admin.py
index 155e84127..40416b07a 100644
--- a/src/authenticators/ldap_admin.py
+++ b/src/authenticators/ldap_admin.py
@@ -16,11 +16,14 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 #
+import jwt
 import os
 import logging
 import ldap
 import ldap.sasl
 import time
+import glob
+import hashlib
 
 from moulinette import m18n
 from moulinette.authentication import BaseAuthenticator
@@ -29,14 +32,21 @@ from moulinette.utils.text import random_ascii
 from yunohost.utils.error import YunohostError, YunohostAuthenticationError
 from yunohost.utils.ldap import _get_ldap_interface
 
-session_secret = random_ascii()
 logger = logging.getLogger("yunohost.authenticators.ldap_admin")
 
+SESSION_SECRET = open("/etc/yunohost/.admin_cookie_secret").read().strip()
+SESSION_FOLDER = "/var/cache/yunohost/sessions"
+SESSION_VALIDITY = 3 * 24 * 3600  # 3 days
+
 LDAP_URI = "ldap://localhost:389"
 ADMIN_GROUP = "cn=admins,ou=groups"
 AUTH_DN = "uid={uid},ou=users,dc=yunohost,dc=org"
 
 
+def short_hash(data):
+    return hashlib.shake_256(data.encode()).hexdigest(20)
+
+
 class Authenticator(BaseAuthenticator):
     name = "ldap_admin"
 
@@ -122,55 +132,90 @@ class Authenticator(BaseAuthenticator):
             if con:
                 con.unbind_s()
 
+        return {"user": uid}
+
     def set_session_cookie(self, infos):
-        from bottle import response
+        from bottle import response, request
 
         assert isinstance(infos, dict)
+        assert "user" in infos
 
-        # This allows to generate a new session id or keep the existing one
-        current_infos = self.get_session_cookie(raise_if_no_session_exists=False)
-        new_infos = {"id": current_infos["id"]}
-        new_infos.update(infos)
+        # Create a session id, built as <user_hash> + some random ascii
+        # Prefixing with the user hash is meant to provide the ability to invalidate all this user's session
+        # (eg because the user gets deleted, or password gets changed)
+        # User hashing not really meant for security, just to sort of anonymize/pseudonymize the session file name
+        infos["id"] = short_hash(infos['user']) + random_ascii(20)
 
         response.set_cookie(
             "yunohost.admin",
-            new_infos,
+            jwt.encode(infos, SESSION_SECRET, algorithm="HS256"),
             secure=True,
-            secret=session_secret,
             httponly=True,
-            path="/"
-            # samesite="strict", # Bottle 0.12 doesn't support samesite, to be added in next versions
+            path="/",
+            samesite="strict",
         )
 
+        # Create the session file (expiration mechanism)
+        session_file = f'{SESSION_FOLDER}/{infos["id"]}'
+        os.system(f'touch "{session_file}"')
+
     def get_session_cookie(self, raise_if_no_session_exists=True):
-        from bottle import request
+        from bottle import request, response
 
         try:
-            # N.B. : here we implicitly reauthenticate the cookie
-            # because it's signed via the session_secret
-            # If no session exists (or if session is invalid?)
-            # it's gonna return the default empty dict,
-            # which we interpret as an authentication failure
-            infos = request.get_cookie(
-                "yunohost.admin", secret=session_secret, default={}
+            token = request.get_cookie("yunohost.admin", default="").encode()
+            infos = jwt.decode(
+                token,
+                SESSION_SECRET,
+                algorithms="HS256",
+                options={"require": ["id", "user"]},
             )
         except Exception:
-            if not raise_if_no_session_exists:
-                return {"id": random_ascii()}
             raise YunohostAuthenticationError("unable_authenticate")
 
-        if not infos and raise_if_no_session_exists:
+        if not infos:
             raise YunohostAuthenticationError("unable_authenticate")
 
-        if "id" not in infos:
-            infos["id"] = random_ascii()
+        self.purge_expired_session_files()
+        session_file = f'{SESSION_FOLDER}/{infos["id"]}'
+        if not os.path.exists(session_file):
+            response.delete_cookie("yunohost.admin", path="/")
+            raise YunohostAuthenticationError("session_expired")
 
-        # FIXME: Here, maybe we want to re-authenticate the session via the authenticator
-        # For example to check that the username authenticated is still in the admin group...
+        # Otherwise, we 'touch' the file to extend the validity
+        os.system(f'touch "{session_file}"')
 
         return infos
 
     def delete_session_cookie(self):
         from bottle import response
 
+        try:
+            infos = self.get_session_cookie()
+            session_file = f'{SESSION_FOLDER}/{infos["id"]}'
+            os.remove(session_file)
+        except Exception as e:
+            logger.debug(f"User logged out, but failed to properly invalidate the session : {e}")
+
         response.delete_cookie("yunohost.admin", path="/")
+
+    def purge_expired_session_files(self):
+
+        for session_id in os.listdir(SESSION_FOLDER):
+            session_file = f"{SESSION_FOLDER}/{session_id}"
+            if abs(os.path.getctime(session_file) - time.time()) > SESSION_VALIDITY:
+                try:
+                    os.remove(session_file)
+                except Exception as e:
+                    logger.debug(f"Failed to delete session file {session_file} ? {e}")
+
+    @staticmethod
+    def invalidate_all_sessions_for_user(user):
+        for path in glob.glob(f"{SESSION_FOLDER}/{short_hash(user)}*"):
+            try:
+                logger.info(path)
+                os.remove(path)
+            except Exception as e:
+                logger.debug(f"Failed to delete session file {path} ? {e}")
+
+        logger.info(str(glob.glob(f"{SESSION_FOLDER}/*")))
diff --git a/src/authenticators/ldap_ynhuser.py b/src/authenticators/ldap_ynhuser.py
index 0a4ab0b75..8b14be0af 100644
--- a/src/authenticators/ldap_ynhuser.py
+++ b/src/authenticators/ldap_ynhuser.py
@@ -20,10 +20,11 @@ from moulinette.authentication import BaseAuthenticator
 from moulinette.utils.text import random_ascii
 from yunohost.utils.error import YunohostError, YunohostAuthenticationError
 
+logger = logging.getLogger("yunohostportal.authenticators.ldap_ynhuser")
+
 SESSION_SECRET = open("/etc/yunohost/.ssowat_cookie_secret").read().strip()
 SESSION_FOLDER = "/var/cache/yunohost-portal/sessions"
 SESSION_VALIDITY = 3 * 24 * 3600  # 3 days
-logger = logging.getLogger("yunohostportal.authenticators.ldap_ynhuser")
 
 URI = "ldap://localhost:389"
 USERDN = "uid={username},ou=users,dc=yunohost,dc=org"
diff --git a/src/user.py b/src/user.py
index 46228805f..1b31df25a 100644
--- a/src/user.py
+++ b/src/user.py
@@ -306,6 +306,7 @@ def user_delete(operation_logger, username, purge=False, from_import=False):
     from yunohost.hook import hook_callback
     from yunohost.utils.ldap import _get_ldap_interface
     from yunohost.authenticators.ldap_ynhuser import Authenticator as PortalAuth
+    from yunohost.authenticators.ldap_admin import Authenticator as AdminAuth
 
     if username not in user_list()["users"]:
         raise YunohostValidationError("user_unknown", user=username)
@@ -335,6 +336,7 @@ def user_delete(operation_logger, username, purge=False, from_import=False):
         raise YunohostError("user_deletion_failed", user=username, error=e)
 
     PortalAuth.invalidate_all_sessions_for_user(username)
+    AdminAuth.invalidate_all_sessions_for_user(username)
 
     # Invalidate passwd to take user deletion into account
     subprocess.call(["nscd", "-i", "passwd"])
@@ -535,6 +537,7 @@ def user_update(
         raise YunohostError("user_update_failed", user=username, error=e)
 
     if "userPassword" in new_attr_dict:
+        logger.info("Invalidating sessions")
         from yunohost.authenticators.ldap_ynhuser import Authenticator as PortalAuth
         PortalAuth.invalidate_all_sessions_for_user(username)
 
@@ -1273,6 +1276,11 @@ def user_group_update(
         except Exception as e:
             raise YunohostError("group_update_failed", group=groupname, error=e)
 
+    if groupname == "admins" and remove:
+        from yunohost.authenticators.ldap_admin import Authenticator as AdminAuth
+        for user in users_to_remove:
+            AdminAuth.invalidate_all_sessions_for_user(user)
+
     if sync_perm:
         permission_sync_to_user()