How do I implement salt into my login for passwords

Question

Salting enhances password security by adding randomness before hashing. What steps are required to correctly implement salting in a login system?

Answer 1

Salting is a crucial technique in enhancing password security by adding randomness to each password before hashing, thereby protecting against attacks like rainbow tables. To implement salting effectively in your login system, follow these steps:

1. Generate a Unique Salt for Each User:

   • For every user, create a unique, random salt. This ensures that even if two users have the same password, their hashes will differ due to distinct salts.
   • Use a secure random number generator to produce salts of sufficient length (e.g., 16 bytes or more) to prevent predictability.

2. Combine the Salt with the User's Password:

   • Concatenate the salt with the user's plaintext password. The order (salt + password or password + salt) should remain consistent throughout your system.

3. Hash the Combined Password and Salt:

   • Apply a cryptographic hash function (e.g., SHA-256) to the concatenated salt and password.
   • For enhanced security, consider using key derivation functions like PBKDF2, bcrypt, or Argon2, which are designed to be computationally intensive, thereby slowing down brute-force attacks.

4. Store the Salt and Hash Securely:

   • Save both the salt and the resulting hash in your database. Typically, they are stored together in a single field, separated by a delimiter, or in separate fields.
   • Ensure that salts are stored in plaintext, as they are not secrets, but are necessary for verifying passwords.

5. Verify Passwords During Login:

   • Retrieve the user's unique salt and the stored hash from the database.
   • Concatenate the salt with the password provided during login and hash this combination using the same method employed during registration.
   • Compare the newly computed hash with the stored hash. If they match, the password is correct; otherwise, it's incorrect.

Example

Consider a user with the password P@ssw0rd!.

• Salt Generation: Generate a random 16-byte salt, e.g., 3f5e8c7d9a1b2c3d4e5f6a7b8c9d0e1f.
• Concatenation: Combine the salt and password: 3f5e8c7d9a1b2c3d4e5f6a7b8c9d0e1fP@ssw0rd!.
• Hashing: Apply a hash function to the combination, resulting in a hash like a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6.
• Storage: Store both the salt and the hash in the database.

Use Cases

• Preventing Rainbow Table Attacks: Even if attackers have precomputed hashes for common passwords, unique salts ensure that the hashes in your system won't match those in the rainbow tables.
• Mitigating Brute-Force Attacks: Using computationally intensive hashing algorithms increases the time required to guess each password, discouraging attackers from attempting large-scale brute-force attacks.

Additional Considerations

• Peppering: Alongside salting, you can add a system-wide secret value (pepper) to passwords before hashing. This adds another layer of security, as attackers would need both the salt and the pepper to crack passwords. Ensure the pepper is stored securely, separate from the database.
• Regular Security Audits: Periodically review and update your password handling procedures to align with current security best practices.

By meticulously implementing salting and combining it with robust hashing techniques, you significantly enhance the security of your login system, protecting user credentials against common attack vectors.