Choosing the Right Password Hashing Algorithm

• Problem with Password Storage
• What is Argon2id?
  • What is a Key Derivation Function (KDF)?
• Why Argon2id?
• Conclusion

Problem with Password Storage

When passwords are stored, they must remain secure even if the database is compromised.

Even if your application has brute-force protection, what happens when an attacker gets the hashes? They can always brute-force them offline.

With older hashing algorithms like MD5 or SHA-1, attackers can compute billions of hashes per second using modern hardware. That makes weak passwords trivial to crack.

So, solution is: slow down offline attacks by using hashing algorithms that are intentionally expensive to compute.

Below is a list of commonly recommended password hashing algorithms:

• Argon2id: Winner of the 2015 Password Hashing Competition. Best choice for new systems. Strong resistance against both GPU-based attacks and side-channel attacks. Minimum recommended parameters: memory = 19 MiB, iterations = 2, parallelism = 1
• scrypt: Good alternative with strong memory hardness. Minimum configuration: N = 2^17, r = 8, p = 1
• bcrypt: Common in legacy systems. Still secure if configured properly. Recommended cost factor: 12+
• PBKDF2: Mostly used when FIPS-140 compliance is required. Minimum configuration: iterations = 600,000, hash = HMAC-SHA256

Avoid fast hashing algorithms like MD5, SHA-1, or even SHA-256 for password hashing. They are designed for speed, which makes them easy to brute-force with modern hardware.

What is Argon2id?

Argon2id is a variant of Argon2. It’s not just a password hashing algorithm — it’s a key derivation function (KDF).

What is a Key Derivation Function (KDF)?

A KDF is used to derive secure cryptographic keys from a secret input (like a password).

Purpose:

• Make brute-force attacks slower
• Increase the cost of guessing each password

In practice, a KDF turns a weak input (human password) into something much harder to attack.

Why Argon2id?

Argon2 has three variants:

• Argon2d Optimized for resistance against GPU attacks (memory-hard), but vulnerable to side-channel attacks.
• Argon2i Resistant to side-channel attacks, but weaker against GPU-based brute-force.
• Argon2id Hybrid approach — combines both. This makes it the most balanced and recommended option.

Besides the security benefits, there are trade-offs:

• More resource-intensive (CPU + memory)
• Slightly more complex to implement correctly

Conclusion

If you’re building a new system, use Argon2id with recommended parameters.

For existing systems, bcrypt is still a safe and practical choice.

Avoid fast hashing algorithms like MD5 or SHA-based hashes for passwords.

The goal is not just to hash passwords, but to make brute-force attacks as expensive as possible.