diff --git a/backend/app.py b/backend/app.py
index bbe337c3..af04255e 100644
--- a/backend/app.py
+++ b/backend/app.py
@@ -1,12 +1,14 @@
 import uvicorn
 from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
 from starlette import status
 from starlette.requests import Request
 from starlette.responses import JSONResponse
 
 from db.errors.database_errors import ActionAlreadyPerformedError, ItemNotFoundError, NoSuchRelationError
-from routes.errors.authentication import InvalidRoleCredentialsError, NoAccessToSubjectError
+from routes.errors.authentication import InvalidAuthenticationError, InvalidRoleCredentialsError, NoAccessToSubjectError
 from routes.group import group_router
+from routes.login import login_router
 from routes.project import project_router
 from routes.student import student_router
 from routes.subject import subject_router
@@ -16,6 +18,7 @@
 app = FastAPI()
 
 # Koppel routes uit andere modules.
+app.include_router(login_router, prefix="/api")
 app.include_router(student_router, prefix="/api")
 app.include_router(teacher_router, prefix="/api")
 app.include_router(users_router, prefix="/api")
@@ -23,10 +26,11 @@
 app.include_router(subject_router, prefix="/api")
 app.include_router(group_router, prefix="/api")
 
-DEBUG = False # Should always be false in repo
+DEBUG = False  # Should always be false in repo
 
 if DEBUG:
     from fastapi.middleware.cors import CORSMiddleware
+
     origins = [
         "https://localhost",
         "https://localhost:8080",
@@ -41,6 +45,7 @@
         allow_headers=["*"],
     )
 
+
 # Koppel de exception handlers
 @app.exception_handler(InvalidRoleCredentialsError)
 def invalid_admin_credentials_error_handler(request: Request, exc: InvalidRoleCredentialsError) -> JSONResponse:
@@ -82,5 +87,13 @@ def no_such_relation_error_handler(request: Request, exc: NoSuchRelationError) -
     )
 
 
+@app.exception_handler(InvalidAuthenticationError)
+def invalid_authentication_error_handler(request: Request, exc: NoSuchRelationError) -> JSONResponse:
+    return JSONResponse(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        content={"detail": str(exc)},
+    )
+
+
 if __name__ == "__main__":
     uvicorn.run("app:app")
diff --git a/backend/controllers/auth/authentication_controller.py b/backend/controllers/auth/authentication_controller.py
new file mode 100644
index 00000000..a8bb2748
--- /dev/null
+++ b/backend/controllers/auth/authentication_controller.py
@@ -0,0 +1,80 @@
+import os
+import string
+from typing import TYPE_CHECKING
+
+import httpx
+from defusedxml.ElementTree import fromstring
+from sqlalchemy.orm import Session
+
+from domain.logic.student import create_student
+from domain.logic.teacher import create_teacher
+from domain.logic.user import get_user_with_email
+from domain.models.UserDataclass import UserDataclass
+
+if TYPE_CHECKING:
+    from _elementtree import Element
+
+cas_service = os.getenv("CAS_URL", "https://localhost:8080/login")
+
+
+def authenticate_user(session: Session, ticket: str) -> UserDataclass | None:
+    """
+    This function will authenticate the user.
+    If the use doesn't yet exist in the database, it will create an entry.
+    a
+
+    :param session: Session with the database
+    :param ticket: A ticket from login.ugent.be/login?service=https://localhost:8080/login
+    :return: None if the authentication failed, user: UseDataclass is the authentication was successful
+    """
+    allowed_chars = set(string.ascii_letters + string.digits + "-")
+    if not all(c in allowed_chars for c in ticket):
+        return None
+    user_information = httpx.get(f"https://login.ugent.be/serviceValidate?service={cas_service}&ticket={ticket}")
+    user_dict: dict | None = parse_cas_xml(user_information.text)
+    if user_dict is None:
+        return None
+
+    user: UserDataclass | None = get_user_with_email(session, user_dict["email"])
+    if user is None:
+        if user_dict["role"] == "student":
+            user = create_student(session, user_dict["name"], user_dict["email"])
+        elif user_dict["role"] == "teacher":
+            user = create_teacher(session, user_dict["name"], user_dict["email"])
+    return user
+
+
+def parse_cas_xml(xml: str) -> dict | None:
+    """
+    The authentication with CAS returns a xml-object.
+    This function will read the necessary attributes and return them in a dictionary.
+
+    :param xml: str: response xml from CAS
+    :return: None if the authentication failed else dict
+    """
+
+    namespace = "{http://www.yale.edu/tp/cas}"
+    root: Element | None = fromstring(xml).find(f"{namespace}authenticationSuccess")
+    if root is None:
+        return None
+    user_information: Element | None = root.find(f"{namespace}attributes")
+    if user_information is None:
+        return None
+    givenname: Element | None = user_information.find(f"{namespace}givenname")
+    surname: Element | None = user_information.find(f"{namespace}surname")
+    email: Element | None = user_information.find(f"{namespace}mail")
+    role: list | None = user_information.findall(f"{namespace}objectClass")
+    if role is not None and givenname is not None and surname is not None and email is not None:
+        role_str = ""
+        for r in role:
+            if r.text == "ugentStudent" and role_str == "":
+                role_str = "student"
+            elif r.text == "ugentEmployee":
+                role_str = "teacher"
+
+        return {
+            "email": email.text.lower(),
+            "name": f"{givenname.text} {surname.text}",
+            "role": role_str,
+        }
+    return None
diff --git a/backend/controllers/auth/token_controller.py b/backend/controllers/auth/token_controller.py
new file mode 100644
index 00000000..ceefcb37
--- /dev/null
+++ b/backend/controllers/auth/token_controller.py
@@ -0,0 +1,25 @@
+import contextlib
+import os
+from datetime import UTC, datetime, timedelta
+
+import jwt
+
+from domain.models.UserDataclass import UserDataclass
+
+# Zeker aanpassen in production
+jwt_secret = os.getenv("JWT_SECRET", "secret")
+
+
+def verify_token(token: str) -> int | None:
+    with contextlib.suppress(jwt.ExpiredSignatureError, jwt.DecodeError):
+        payload = jwt.decode(token, jwt_secret, algorithms=["HS256"])
+        return payload.get("uid", None)
+
+
+def create_token(user: UserDataclass) -> str:
+    expire = datetime.now(UTC) + timedelta(days=1)
+    to_encode: dict = {
+        "uid": user.id,
+        "exp": expire,
+    }
+    return jwt.encode(to_encode, jwt_secret, algorithm="HS256")
diff --git a/backend/domain/logic/user.py b/backend/domain/logic/user.py
index b3f25f9b..1125191a 100644
--- a/backend/domain/logic/user.py
+++ b/backend/domain/logic/user.py
@@ -1,3 +1,4 @@
+from sqlalchemy import select
 from sqlalchemy.orm import Session
 
 from db.models.models import Admin, Student, Teacher, User
@@ -29,6 +30,20 @@ def get_user(session: Session, user_id: int) -> UserDataclass:
     return get(session, User, user_id).to_domain_model()
 
 
+def get_user_with_email(session: Session, email: str) -> UserDataclass | None:
+    stmt = select(User).where(User.email == email)
+    result = session.execute(stmt)
+    users = [r.to_domain_model() for r in result.scalars()]
+
+    if len(users) > 1:
+        raise NotImplementedError
+
+    if len(users) == 1:
+        return users[0]
+
+    return None
+
+
 def get_all_users(session: Session) -> list[UserDataclass]:
     return [user.to_domain_model() for user in get_all(session, User)]
 
diff --git a/backend/domain/models/APIUser.py b/backend/domain/models/APIUser.py
index c37fb477..c4ec1a67 100644
--- a/backend/domain/models/APIUser.py
+++ b/backend/domain/models/APIUser.py
@@ -8,3 +8,7 @@ class APIUser(BaseModel):
     name: str
     email: EmailStr
     roles: list[Role]
+
+
+class LoginResponse(BaseModel):
+    token: str
diff --git a/backend/requirements.txt b/backend/requirements.txt
index 2e62ebad..7041d175 100644
--- a/backend/requirements.txt
+++ b/backend/requirements.txt
@@ -21,3 +21,7 @@ SQLAlchemy==2.0.27
 starlette==0.36.3
 typing_extensions==4.10.0
 uvicorn==0.27.1
+httpx==0.27.0
+defusedxml~=0.7.1
+cryptography~=42.0.5
+PyJWT~=2.8.0
\ No newline at end of file
diff --git a/backend/routes/dependencies/role_dependencies.py b/backend/routes/dependencies/role_dependencies.py
index 9de95992..559c08ba 100644
--- a/backend/routes/dependencies/role_dependencies.py
+++ b/backend/routes/dependencies/role_dependencies.py
@@ -1,6 +1,8 @@
 from fastapi import Depends
+from fastapi.security import APIKeyHeader
 from sqlalchemy.orm import Session
 
+from controllers.auth.token_controller import verify_token
 from db.sessions import get_session
 from domain.logic.admin import get_admin, is_user_admin
 from domain.logic.group import get_group
@@ -13,35 +15,47 @@
 from domain.models.TeacherDataclass import TeacherDataclass
 from routes.errors.authentication import (
     InvalidAdminCredentialsError,
+    InvalidAuthenticationError,
     InvalidStudentCredentialsError,
     InvalidTeacherCredentialsError,
     NoAccessToSubjectError,
 )
 
+auth_scheme = APIKeyHeader(name="cas")
 
-def get_authenticated_user() -> int:
-    return 1  # Checken of een user bestaat en/of hij de juiste credentials heeft.
 
+def get_authenticated_user(token: str = Depends(auth_scheme)) -> int:
+    uid = verify_token(token)
+    if uid is None:
+        raise InvalidAuthenticationError
+    return uid
 
-def get_authenticated_admin(session: Session = Depends(get_session)) -> AdminDataclass:
-    user_id = get_authenticated_user()
-    if not is_user_admin(session, user_id):
+
+def get_authenticated_admin(
+    session: Session = Depends(get_session),
+    uid: int = Depends(get_authenticated_user),
+) -> AdminDataclass:
+    if not is_user_admin(session, uid):
         raise InvalidAdminCredentialsError
-    return get_admin(session, user_id)
+    return get_admin(session, uid)
 
 
-def get_authenticated_teacher(session: Session = Depends(get_session)) -> TeacherDataclass:
-    user_id = get_authenticated_user()
-    if not is_user_teacher(session, user_id):
+def get_authenticated_teacher(
+    session: Session = Depends(get_session),
+    uid: int = Depends(get_authenticated_user),
+) -> TeacherDataclass:
+    if not is_user_teacher(session, uid):
         raise InvalidTeacherCredentialsError
-    return get_teacher(session, user_id)
+    return get_teacher(session, uid)
 
 
-def get_authenticated_student(session: Session = Depends(get_session)) -> StudentDataclass:
-    user_id = get_authenticated_user()
-    if not is_user_student(session, user_id):
+def get_authenticated_student(
+    session: Session = Depends(get_session),
+    uid: int = Depends(get_authenticated_user),
+) -> StudentDataclass:
+    if not is_user_student(session, uid):
         raise InvalidStudentCredentialsError
-    return get_student(session, user_id)
+    return get_student(session, uid)
 
 
 def ensure_user_authorized_for_subject(
diff --git a/backend/routes/errors/authentication.py b/backend/routes/errors/authentication.py
index 4c51dd14..8c9b507d 100644
--- a/backend/routes/errors/authentication.py
+++ b/backend/routes/errors/authentication.py
@@ -16,3 +16,7 @@ class InvalidStudentCredentialsError(InvalidRoleCredentialsError):
 
 class NoAccessToSubjectError(Exception):
     ERROR_MESSAGE = "User doesn't have access to subject"
+
+
+class InvalidAuthenticationError(Exception):
+    ERROR_MESSAGE = "User is not authenticated"
diff --git a/backend/routes/login.py b/backend/routes/login.py
index e69de29b..d7d43773 100644
--- a/backend/routes/login.py
+++ b/backend/routes/login.py
@@ -0,0 +1,33 @@
+from fastapi import APIRouter, Depends
+from sqlalchemy.orm import Session
+
+from controllers.auth.authentication_controller import authenticate_user
+from controllers.auth.token_controller import create_token
+from db.sessions import get_session
+from domain.models.APIUser import LoginResponse
+from domain.models.UserDataclass import UserDataclass
+from routes.errors.authentication import InvalidAuthenticationError
+
+# test url: https://login.ugent.be/login?service=https://localhost:8080/api/login
+login_router = APIRouter()
+
+
+@login_router.get("/login")
+def login(
+    ticket: str,
+    session: Session = Depends(get_session),
+) -> LoginResponse:
+    """
+    This function starts a session for the user.
+    For authentication, it uses the given ticket and the UGent CAS server (https://login.ugent.be).
+
+    :param session:
+    :param ticket: str:  A UGent CAS ticket that will be used for authentication.
+    :return:
+        - Valid Ticket: Response: with a JWT token;
+        - Invalid Ticket: Response: with status_code 401 (unauthenticated) and an error message
+    """
+    user: UserDataclass | None = authenticate_user(session, ticket)
+    if not user:
+        raise InvalidAuthenticationError
+    return LoginResponse(token=create_token(user))
diff --git a/backend/routes/user.py b/backend/routes/user.py
index ceb208e7..e3544546 100644
--- a/backend/routes/user.py
+++ b/backend/routes/user.py
@@ -5,7 +5,7 @@
 from db.sessions import get_session
 from domain.logic.basic_operations import get, get_all
 from domain.logic.role_enum import Role
-from domain.logic.user import convert_user, modify_user_roles
+from domain.logic.user import convert_user, get_user, modify_user_roles
 from domain.models.APIUser import APIUser
 from domain.models.UserDataclass import UserDataclass
 from routes.dependencies.role_dependencies import get_authenticated_admin, get_authenticated_user
@@ -16,10 +16,9 @@
 @users_router.get("/user")
 def get_current_user(
     session: Session = Depends(get_session),
-    user_id: int = Depends(get_authenticated_user),
+    uid: int = Depends(get_authenticated_user),
 ) -> APIUser:
-    user: UserDataclass = get(session, User, user_id).to_domain_model()
-    return convert_user(session, user)
+    return convert_user(session, get_user(session, uid))
 
 
 @users_router.get("/users", dependencies=[Depends(get_authenticated_admin)])
@@ -29,7 +28,7 @@ def get_users(session: Session = Depends(get_session)) -> list[APIUser]:
 
 
 @users_router.get("/users/{uid}", dependencies=[Depends(get_authenticated_admin)])
-def get_user(uid: int, session: Session = Depends(get_session)) -> APIUser:
+def admin_get_user(uid: int, session: Session = Depends(get_session)) -> APIUser:
     user: UserDataclass = get(session, User, uid).to_domain_model()
     return convert_user(session, user)
 
diff --git a/backend/tests/authentication_test.py b/backend/tests/authentication_test.py
new file mode 100644
index 00000000..fdc5f66d
--- /dev/null
+++ b/backend/tests/authentication_test.py
@@ -0,0 +1,14 @@
+import unittest
+
+from fastapi.testclient import TestClient
+
+from app import app
+
+
+class AuthenticationTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.app = TestClient(app)
+
+
+if __name__ == "__main__":
+    unittest.main()