Bcrypt Vs Argon2 ; Is Bcrypt Really Outdated ?

When I was in college, My teacher introduced the password hashing algorithms to me. That time he taught me why hashed passwords are necessary in an application and which one should we choose among Bcrypt, MD5, SHA and PBKDF Etc., Since that time I became the Bcrypt loyalist until i got to know about Argon2id and then that one questions wondered me “is Bcrypt really outdated ?”. So let's break this down.

Before we move forward let's see;

What is Password Hashing, and Why Is It Necessary?

Password hashing is the process of transforming a password into a fixed-length string of characters using a cryptographic hash function. This hashed output is what gets stored in a database, not the actual password.

Why do we hash passwords?

Security: Storing raw passwords is a critical security risk. If your database is ever compromised, hashed passwords protect users from having their actual passwords exposed.

Irreversibility: Hash functions are designed to be one-way, meaning it's computationally infeasible to reverse the hash back into the original password.

Verification without storage: When a user logs in, the password they provide is hashed and compared with the stored hash. If they match, access is granted, without ever needing to store the plain-text password.

Bcrypt Vs Argon2 : A Comparison

When it comes to hashing passwords, two names often come up: Bcrypt and Argon2. Both are secure, but they take very different approaches.

Bcrypt, developed in 1999, is based on the Blowfish cipher. It’s been trusted for over two decades, mainly because of its simplicity and adaptability. One of its core features is the work factor (or cost), which allows developers to adjust the computational difficulty of hashing. As hardware improves, the cost can be increased to make brute-force attacks slower and more expensive.

Bcrypt is also very lightweight in terms of memory usage, making it ideal for environments where RAM is limited. It’s widely supported across platforms and programming languages like Node.js, PHP, Python, and Ruby, which adds to its convenience.

But Bcrypt isn’t perfect. It’s primarily CPU-bound, meaning it doesn’t take advantage of modern hardware capabilities like multi-threading or high memory usage. It’s also more vulnerable to hardware-accelerated attacks (e.g., using GPUs or ASICs) compared to newer algorithms. Additionally, it lacks resistance to side-channel attacks and doesn’t support parallel computation, which is a missed opportunity in today’s multi-core world.

Enter Argon2, the winner of the Password Hashing Competition (PHC) in 2015. Argon2 was specifically designed to address many of Bcrypt’s shortcomings. It comes in three flavors:

• Argon2d: Best for internal systems and high-speed hashing; less resistant to side-channel attacks.

• Argon2i: Focused on side-channel resistance, using data-independent memory access.

• Argon2id: A hybrid of both, offering a balanced approach and generally considered the recommended default.

What makes Argon2 powerful is its memory-hardness, it requires a significant amount of memory to compute hashes. This makes it extremely resistant to GPU and ASIC attacks, which typically rely on fast, parallel computation with limited memory.

It also supports parallelism, allowing the algorithm to use multiple CPU cores. Developers can configure parameters such as memory usage, iteration count, and threads to tailor the hash function to their specific environment and threat model. However, this flexibility also comes with complexity, and implementing Argon2 securely requires more care than Bcrypt.

So… Is Bcrypt Really Outdated ?

That’s the million-dollar question. And the answer isn’t as simple as yes or no.

While Bcrypt is certainly older, it’s far from obsolete. Its long-standing track record, widespread support, and reliability make it a solid choice for many applications, especially those that don’t require top-of-the-line defense against modern attack techniques.

In fact, for small to mid-scale applications or legacy systems, Bcrypt might still be the better choice. It’s easier to implement, consumes less memory, and works well on low-resource servers. Plus, if it’s already embedded in your system and hasn’t caused issues, there’s likely no urgent reason to migrate.

However, Argon2 is clearly the future. Its ability to resist modern hardware attacks, leverage multi-core CPUs, and adapt to different environments gives it a significant edge, especially for applications that demand high security or expect to scale.

If you're building a new system today or working on an application that deals with sensitive user data, Argon2id is the recommended go-to. It’s future-ready, better aligned with current hardware trends, and more resilient against evolving attack vectors.

Final Thoughts;

Bcrypt isn’t outdated, it’s just not evolving. It still does its job well, and in many cases, it’s more than enough. But as attackers get smarter and hardware gets faster, password security needs to keep up.

Think of Bcrypt as the sturdy old lock that’s kept your door secure for years. Argon2 is the new smart lock with fingerprint access, encryption, and an alarm system. Both can secure your house, but which one you choose depends on what you’re protecting, and from whom.

So if you’re starting fresh or looking for future-proof security, give Argon2id a serious look. But if you're running a trusted system using Bcrypt properly, don’t panic, it’s still a strong defense.