diff --git a/README.md b/README.md
index 03030f229..a47814229 100644
--- a/README.md
+++ b/README.md
@@ -48,3 +48,20 @@ source .venv/bin/activate
 pip install -r requirements.txt
 streamlit run Chatbot.py
 ```
+
+
+## Karla's part
+
+```bash
+cd "/Users/karla/Desktop/Soft Eng/llm-examples" && rm -rf .venv && /opt/homebrew/bin/python3.11 -m venv .venv && "./.venv/bin/python" -m pip install --upgrade pip setuptools wheel && "./.venv/bin/python" -m pip install streamlit cryptography pytest -q
+```
+
+```bash
+cd "/Users/karla/Desktop/Soft Eng/llm-examples" && "./.venv/bin/python" -m pip install streamlit cryptography pytest -q
+```
+
+```bash
+cd "/Users/karla/Desktop/Soft Eng/llm-examples" && "./.venv/bin/python" -m pytest tests/test_auth_encrypt.py -vv
+```
+
+### or instead of -vv use -q
diff --git a/auth_encrypt.py b/auth_encrypt.py
new file mode 100644
index 000000000..dd3634e1d
--- /dev/null
+++ b/auth_encrypt.py
@@ -0,0 +1,108 @@
+"""
+Simple history encryption helper using password-based key derivation.
+
+Public API:
+- create_decrypt_key(password, salt=None): Generate salt and derive encryption key from password
+- encrypt_history(plaintext, password, salt): Encrypt bytes using AES-GCM with PBKDF2-derived key
+- decrypt_history(ciphertext, password, salt): Decrypt bytes using AES-GCM with PBKDF2-derived key
+
+"""
+from __future__ import annotations
+
+import base64
+import os
+from typing import Tuple
+
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
+from cryptography.hazmat.primitives.ciphers.aead import AESGCM
+
+
+def create_decrypt_key(password: str, salt: bytes = None) -> Tuple[bytes, bytes]:
+    """Generate a random salt and derive a 32-byte encryption key from password using PBKDF2-HMAC-SHA256.
+    
+    Args:
+        password: User password
+        salt: Optional salt bytes (16 bytes). If None, generates random salt.
+    
+    Returns:
+        (salt, key) tuple where:
+        - salt: 16-byte random salt (store this with encrypted data)
+        - key: 32-byte derived key for encryption/decryption
+    """
+    if salt is None:
+        salt = os.urandom(16)
+    
+    kdf = PBKDF2HMAC(
+        algorithm=hashes.SHA256(),
+        length=32,
+        salt=salt,
+        iterations=200_000,
+    )
+    key = kdf.derive(password.encode("utf-8"))
+    return salt, key
+
+
+def encrypt_history(plaintext: bytes, password: str, salt: bytes) -> bytes:
+    """Encrypt plaintext using AES-GCM with a key derived from password and salt.
+    
+    Args:
+        plaintext: Data to encrypt
+        password: User password
+        salt: 16-byte salt (from create_decrypt_key)
+    
+    Returns:
+        Encrypted bytes in format: nonce (12 bytes) + ciphertext
+    """
+    _, key = create_decrypt_key(password, salt)
+    aes = AESGCM(key)
+    nonce = os.urandom(12)
+    ciphertext = aes.encrypt(nonce, plaintext, associated_data=None)
+    return nonce + ciphertext
+
+
+def decrypt_history(encrypted_data: bytes, password: str, salt: bytes) -> bytes:
+    """Decrypt data encrypted with encrypt_history.
+    
+    Args:
+        encrypted_data: Encrypted bytes (nonce + ciphertext)
+        password: User password
+        salt: 16-byte salt used during encryption
+    
+    Returns:
+        Decrypted plaintext bytes
+        
+    Raises:
+        cryptography.exceptions.InvalidTag: If password/salt incorrect or data corrupted
+    """
+    _, key = create_decrypt_key(password, salt)
+    nonce = encrypted_data[:12]
+    ciphertext = encrypted_data[12:]
+    aes = AESGCM(key)
+    plaintext = aes.decrypt(nonce, ciphertext, associated_data=None)
+    return plaintext
+
+
+if __name__ == "__main__":
+    # Quick local demo
+    demo_pw = "s3cret!"
+    demo_text = b"Hello! This is a secret document."
+
+    # Create key with random salt
+    salt, key = create_decrypt_key(demo_pw)
+    print(f"Generated salt: {base64.b64encode(salt).decode()}")
+    
+    # Encrypt
+    encrypted = encrypt_history(demo_text, demo_pw, salt)
+    print(f"Encrypted {len(encrypted)} bytes")
+    
+    # Decrypt
+    decrypted = decrypt_history(encrypted, demo_pw, salt)
+    print(f"Decrypted: {decrypted.decode()}")
+    
+    # Verify wrong password fails
+    try:
+        decrypt_history(encrypted, "wrong-password", salt)
+        print("ERROR: Should have failed!")
+    except Exception as e:
+        print(f"Wrong password correctly rejected: {type(e).__name__}")
diff --git a/auth_encrypt.py.bak b/auth_encrypt.py.bak
new file mode 100644
index 000000000..839f306a2
--- /dev/null
+++ b/auth_encrypt.py.bak
@@ -0,0 +1,166 @@
+"""
+Simple auth + file encryption helper.
+
+Features:
+- Create user: generates salt, derives a key from password (PBKDF2-HMAC-SHA256), stores verifier and encrypts provided bytes with AES-GCM.
+- Verify user: derives key and compares against stored verifier.
+- Decrypt user file: locate encrypted file and decrypt with derived key.
+
+Storage:
+- users.json in repository root stores entries like {
+    username: { salt: base64, kdf_iterations: int, pw_verifier: base64, enc_filename: str }
+}
+"""
+from __future__ import annotations
+
+import base64
+import json
+import os
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Optional, Tuple
+
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
+from cryptography.hazmat.primitives.ciphers.aead import AESGCM
+
+# Config
+_ROOT = Path(__file__).resolve().parent
+_USERS_FILE = _ROOT / "users.json"
+_USER_DATA_DIR = _ROOT / "user_data"
+_USER_DATA_DIR.mkdir(exist_ok=True)
+
+
+def _load_users() -> dict:
+    if not _USERS_FILE.exists():
+        return {}
+    with _USERS_FILE.open("r", encoding="utf-8") as f:
+        return json.load(f)
+
+
+def _save_users(data: dict) -> None:
+    with _USERS_FILE.open("w", encoding="utf-8") as f:
+        json.dump(data, f, indent=2)
+
+
+def _derive_key(password: str, salt: bytes, iterations: int = 200_000) -> bytes:
+    """Derive a 32-byte key from password and salt using PBKDF2-HMAC-SHA256."""
+    kdf = PBKDF2HMAC(
+        algorithm=hashes.SHA256(),
+        length=32,
+        salt=salt,
+        iterations=iterations,
+    )
+    return kdf.derive(password.encode("utf-8"))
+
+
+def _verify_key(password: str, salt: bytes, expected: bytes, iterations: int = 200_000) -> bool:
+    """Return True if password derives to expected key. Uses exception semantics from KDF verify via try/except."""
+    kdf = PBKDF2HMAC(
+        algorithm=hashes.SHA256(),
+        length=32,
+        salt=salt,
+        iterations=iterations,
+    )
+    try:
+        kdf.verify(password.encode("utf-8"), expected)
+        return True
+    except Exception:
+        return False
+
+
+def create_user(username: str, password: str, plaintext: bytes) -> Tuple[bool, str]:
+    """Create a new user entry and encrypt provided plaintext.
+
+    Returns (success, message).
+    If username exists, returns False.
+    """
+    users = _load_users()
+    if username in users:
+        return False, "username already exists"
+
+    salt = os.urandom(16)
+    iterations = 200_000
+    key = _derive_key(password, salt, iterations=iterations)
+
+    # encrypt
+    aes = AESGCM(key)
+    nonce = os.urandom(12)
+    ct = aes.encrypt(nonce, plaintext, associated_data=None)
+
+    enc_filename = f"{username}.enc"
+    enc_path = _USER_DATA_DIR / enc_filename
+    # store as base64: nonce + ciphertext
+    with enc_path.open("wb") as f:
+        f.write(base64.b64encode(nonce + ct))
+
+    users[username] = {
+        "salt": base64.b64encode(salt).decode("utf-8"),
+        "kdf_iterations": iterations,
+        "pw_verifier": base64.b64encode(key).decode("utf-8"),
+        "enc_filename": enc_filename,
+    }
+    _save_users(users)
+    return True, f"user created, encrypted file saved to user_data/{enc_filename}"
+
+
+def verify_user(username: str, password: str) -> Tuple[bool, Optional[bytes]]:
+    """Verify username/password. If ok, returns (True, key) where key is the derived key used for encryption/decryption.
+    If failure, (False, None).
+    """
+    users = _load_users()
+    info = users.get(username)
+    if not info:
+        return False, None
+    salt = base64.b64decode(info["salt"])
+    iterations = int(info.get("kdf_iterations", 200_000))
+    expected = base64.b64decode(info["pw_verifier"])
+    # verify
+    ok = _verify_key(password, salt, expected, iterations=iterations)
+    if not ok:
+        return False, None
+    key = _derive_key(password, salt, iterations=iterations)
+    return True, key
+
+
+def decrypt_user_file(username: str, key: bytes) -> Tuple[bool, Optional[bytes], str]:
+    """Attempt to locate and decrypt the user's encrypted file.
+
+    Returns (success, plaintext_bytes_or_None, message).
+    """
+    users = _load_users()
+    info = users.get(username)
+    if not info:
+        return False, None, "user not found"
+    enc_filename = info.get("enc_filename")
+    if not enc_filename:
+        return False, None, "no encrypted file for user"
+    enc_path = _USER_DATA_DIR / enc_filename
+    if not enc_path.exists():
+        return False, None, f"encrypted file {enc_filename} missing"
+    data = base64.b64decode(enc_path.read_bytes())
+    nonce = data[:12]
+    ct = data[12:]
+    aes = AESGCM(key)
+    try:
+        pt = aes.decrypt(nonce, ct, associated_data=None)
+        return True, pt, "decrypted"
+    except Exception as e:
+        return False, None, f"decryption failed: {e}"
+
+
+if __name__ == "__main__":
+    # Quick local demo
+    demo_user = "alice"
+    demo_pw = "s3cret!"
+    demo_text = b"Hello Alice! This is a secret document."
+
+    ok, msg = create_user(demo_user, demo_pw, demo_text)
+    print(ok, msg)
+    ok, key = verify_user(demo_user, demo_pw)
+    print("verify", ok)
+    if ok:
+        ok2, pt, m = decrypt_user_file(demo_user, key)
+        print(ok2, m)
+        if ok2:
+            print(pt.decode())
diff --git a/pages/6_Login_Encrypt.py b/pages/6_Login_Encrypt.py
new file mode 100644
index 000000000..e78ad9636
--- /dev/null
+++ b/pages/6_Login_Encrypt.py
@@ -0,0 +1,55 @@
+import base64
+from pathlib import Path
+
+import streamlit as st
+
+from auth_encrypt import create_user, verify_user, decrypt_user_file, _USER_DATA_DIR
+
+
+st.set_page_config(page_title="Login + Encrypt Demo")
+
+st.title("🔒 Login and File Encryption Demo")
+
+mode = st.radio("Mode", ["Login", "Create account"])
+
+username = st.text_input("Username")
+password = st.text_input("Password", type="password")
+
+if mode == "Create account":
+    uploaded = st.file_uploader("Upload a file to encrypt for this user", type=None)
+    if st.button("Create account and encrypt"):
+        if not username or not password or not uploaded:
+            st.error("Provide username, password and a file to encrypt")
+        else:
+            data = uploaded.read()
+            ok, msg = create_user(username, password, data)
+            if ok:
+                st.success(msg)
+                # offer download of encrypted file
+                enc_path = _USER_DATA_DIR / f"{username}.enc"
+                if enc_path.exists():
+                    enc_bytes = enc_path.read_bytes()
+                    st.download_button("Download encrypted file", enc_bytes, file_name=f"{username}.enc")
+            else:
+                st.error(msg)
+
+else:
+    if st.button("Login and decrypt user's stored file"):
+        if not username or not password:
+            st.error("Provide username and password")
+        else:
+            ok, key = verify_user(username, password)
+            if not ok:
+                st.error("Invalid username or password")
+            else:
+                ok2, pt, m = decrypt_user_file(username, key)
+                if not ok2:
+                    st.error(m)
+                else:
+                    # try to render as text if possible
+                    try:
+                        text = pt.decode("utf-8")
+                        st.text_area("Decrypted content", value=text, height=300)
+                    except Exception:
+                        st.success("File decrypted — binary data")
+                        st.download_button("Download decrypted file", pt, file_name=f"{username}.decrypted")
diff --git a/requirements.txt b/requirements.txt
index 36459684e..04630d8ed 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,3 +6,4 @@ anthropic>=0.3.0
 trubrics>=1.4.3
 streamlit-feedback
 langchain-community
+cryptography>=40.0.2
diff --git a/tests/test_auth_encrypt.py b/tests/test_auth_encrypt.py
new file mode 100644
index 000000000..20a2fd879
--- /dev/null
+++ b/tests/test_auth_encrypt.py
@@ -0,0 +1,69 @@
+import pytest
+from cryptography.exceptions import InvalidTag
+
+import auth_encrypt
+
+
+def test_create_decrypt_key():
+    """Test salt generation and key derivation."""
+    password = "test-pass-123"
+    
+    # Generate new salt and key
+    salt1, key1 = auth_encrypt.create_decrypt_key(password)
+    assert len(salt1) == 16
+    assert len(key1) == 32
+    
+    # Same password with different salt produces different key
+    salt2, key2 = auth_encrypt.create_decrypt_key(password)
+    assert salt1 != salt2
+    assert key1 != key2
+    
+    # Same password with same salt produces same key
+    _, key3 = auth_encrypt.create_decrypt_key(password, salt=salt1)
+    assert key1 == key3
+
+
+def test_encrypt_decrypt_cycle():
+    """Test full encrypt/decrypt cycle with correct password."""
+    password = "s3cret-password"
+    plaintext = b"Secret data for pytest"
+    
+    # Generate salt and encrypt
+    salt, _ = auth_encrypt.create_decrypt_key(password)
+    encrypted = auth_encrypt.encrypt_history(plaintext, password, salt)
+    
+    # Verify encrypted data is longer (nonce + ciphertext + auth tag)
+    assert len(encrypted) > len(plaintext)
+    assert encrypted != plaintext
+    
+    # Decrypt with correct password
+    decrypted = auth_encrypt.decrypt_history(encrypted, password, salt)
+    assert decrypted == plaintext
+
+
+def test_wrong_password_fails():
+    """Test that wrong password raises exception during decryption."""
+    password = "correct-password"
+    wrong_password = "wrong-password"
+    plaintext = b"Secret message"
+    
+    salt, _ = auth_encrypt.create_decrypt_key(password)
+    encrypted = auth_encrypt.encrypt_history(plaintext, password, salt)
+    
+    # Wrong password should raise InvalidTag
+    with pytest.raises(InvalidTag):
+        auth_encrypt.decrypt_history(encrypted, wrong_password, salt)
+
+
+def test_wrong_salt_fails():
+    """Test that wrong salt raises exception during decryption."""
+    password = "password123"
+    plaintext = b"Another secret"
+    
+    salt, _ = auth_encrypt.create_decrypt_key(password)
+    encrypted = auth_encrypt.encrypt_history(plaintext, password, salt)
+    
+    # Different salt should fail
+    wrong_salt, _ = auth_encrypt.create_decrypt_key(password)
+    with pytest.raises(InvalidTag):
+        auth_encrypt.decrypt_history(encrypted, password, wrong_salt)
diff --git a/user_data/alice.enc b/user_data/alice.enc
new file mode 100644
index 000000000..9842829bc
--- /dev/null
+++ b/user_data/alice.enc
@@ -0,0 +1 @@
+3o3Fgvrt3vgNaYjUvDPqufZvu3a/HXJ5W7kU4DTLK0cjIJXYptHHhML01lLb2D1vRM9VOpDBoBor9iY51KpT0oEiMA==
\ No newline at end of file
diff --git a/users.json b/users.json
new file mode 100644
index 000000000..16aee35f8
--- /dev/null
+++ b/users.json
@@ -0,0 +1,8 @@
+{
+  "alice": {
+    "salt": "hSt0WBARDoVPVNBnOKc6xw==",
+    "kdf_iterations": 200000,
+    "pw_verifier": "9vP6YOXKzFWrhCgFVqfk7crFKbbAtx4+UeN6Iu1emPs=",
+    "enc_filename": "alice.enc"
+  }
+}
\ No newline at end of file