What are the best practices for secure password hashing and session cookie storage?

Use Argon2id (or bcrypt $2b$) with a per‑user random salt and store the hash in a dedicated password column, and set session cookies with the Secure, HttpOnly, SameSite=Strict attributes and a short expiration.

1. Hash selection
- Prefer Argon2id (memory‑hard) for new systems; fall back to bcrypt $2b$ if library support is limited.
- Minimum parameters: Argon2id t=2, m=64 MiB, p=2; bcrypt cost ≥ 12.
2. Implementation (Python)

   from argon2 import PasswordHasher
   ph = PasswordHasher(time_cost=2, memory_cost=65536, parallelism=2, hash_len=32, salt_len=16)
   hash = ph.hash(user_password)
   # Verify
   ph.verify(hash, candidate_password)
   ```
3. **Implementation (Node/Express)**
   ```javascript
   const session = require('express-session');
   app.use(session({
     secret: crypto.randomBytes(64).toString('hex'),
     cookie: {
       httpOnly: true,
       secure: true,          // requires HTTPS
       sameSite: 'strict',
       maxAge: 15 * 60 * 1000 // 15 min inactivity timeout
     },
     resave: false,
     saveUninitialized: false
   }));
   ```
4. **Storage**
   - Store only the hash and its parameters; never keep the plain password or the salt separately.
   - Use a CHAR(255) column with binary collation to avoid encoding issues.
5. **Rotation**
   - On successful login, check `ph.check_needs_rehash(hash)` (or bcrypt `bcrypt.getRounds`). If true, re‑hash with current parameters and update the DB.
6. **Verification timing**
   - Ensure constant‑time comparison; libraries above already provide it.

**Algorithm comparison**

Algorithm | Memory (KB) | Time (ms) | Parallelism
Argon2id | 64‑256 | 100‑300 | 2‑4
bcrypt | N/A | 100‑200 | N/A
scrypt | 64‑128 | 150‑350 | 2‑8
```

Gotcha: If your load balancer terminates TLS, add the Secure cookie flag after TLS re‑encryption; otherwise the flag is stripped and the cookie may be sent over HTTP.