Bcrypt Generator – Create and Verify Password Hashes

Bcrypt generator: create and verify password hashes at the push of a button

With our free bcrypt generator you can create secure bcrypt hashes with a freely selectable cost factor in seconds – and conversely check whether a plaintext matches an existing hash. The entire computation is performed with the JavaScript library bcryptjs directly in your browser – entirely local, with no data transfer to a server.

Whether you, as a developer, need a test password for your database seeds, want to reset an admin account, maintain a .htpasswd file or simply understand how password hashing works: our bcrypt generator delivers standard-compliant hashes at the click of a button that are compatible with PHP, Node.js, Python, Java and all common bcrypt implementations.

What is bcrypt?

Bcrypt is a password hashing function developed in 1999 by Niels Provos and David Mazières for the OpenBSD operating system. It is based on the Blowfish encryption algorithm and was designed for a single purpose: to store passwords in such a way that they cannot be reconstructed without enormous effort, even in the event of a database leak.

The central idea of bcrypt is the adaptive cost factor: while hardware keeps getting faster over the years, the computational effort of bcrypt can simply be scaled along with it. A higher cost factor doubles the number of internal rounds with each step – and thus the time an attacker has to spend on every single guessing attempt. This keeps bcrypt a reliable standard even more than 25 years after its release.

Why bcrypt instead of MD5 or SHA-256?

General-purpose hash functions such as MD5 or SHA-256 were designed for speed – which is exactly what makes them unsuitable for passwords. A modern graphics card computes tens of billions of MD5 hashes per second and thereby runs through entire dictionaries in fractions of a second. Bcrypt, on the other hand, is deliberately slow and reduces an attacker's rate to a few thousand attempts per second – a difference of several orders of magnitude.

On top of that come two further decisive advantages:

• Integrated salt: Bcrypt automatically generates a random salt for every hash and stores it within the hash. Rainbow table attacks with precomputed hashes thus come to nothing – and identical passwords produce different hashes.
• GPU resistance: Bcrypt's memory-intensive internal structure is considerably harder to parallelise on graphics cards than simple hash functions such as MD5 or SHA.
• Future-proofing: If computing power increases, you simply raise the cost factor – without having to switch the algorithm.

Structure of a bcrypt hash

A bcrypt hash is always exactly 60 characters long and follows a fixed scheme, for example $2b$12$R9h/cIPz0gi.URNNX3kh2OPST9/PgBkqquzi.Ss7KIUgO2t0jWMUW:

• $2b$ – algorithm version: Denotes the bcrypt revision. $2a$ is the original variant, $2y$ the PHP revision after a bugfix in 2011, $2b$ the current OpenBSD revision. All are compatible in practice.
• 12$ – cost factor: The number of rounds as a power of two: 2¹² = 4,096 iterations.
• Salt – the next 22 characters: The randomly generated salt in bcrypt base64 encoding.
• Hash – the last 31 characters: The actual hash value derived from password, salt and cost factor.

Because salt and cost factor are contained in the hash, an application needs no additional information to verify a password – the hash is fully self-describing.

The cost factor: security vs. performance

The cost factor (also called work factor or rounds) determines how compute-intensive the hashing is: at cost 12, bcrypt runs through 2¹² = 4,096 internal rounds, at cost 13 it is already 8,192. Each step therefore doubles the computation time – for you as well as for every attacker.

As a rule of thumb for production use: choose the highest cost factor at which a hash is still computed in roughly 100 to 500 milliseconds on your server hardware. For current hardware that means cost 12 as the recommended minimum; security-critical systems use 13 or 14. Values below 10 are considered insufficient today. With our bcrypt generator you can try out different cost factors directly and observe the computation time live in your browser.

Bcrypt in practice: code examples

The hashes created with our generator are fully compatible with all common bcrypt implementations. Here is how to use bcrypt in your own application:

PHP

// Create hash (bcrypt is the default algorithm)
$hash = password_hash($password, PASSWORD_BCRYPT, ['cost' => 12]);

// Verify password
if (password_verify($password, $hash)) {
    // Login successful
}

// Check whether the hash needs an upgrade (e.g. higher cost factor)
if (password_needs_rehash($hash, PASSWORD_BCRYPT, ['cost' => 12])) {
    $hash = password_hash($password, PASSWORD_BCRYPT, ['cost' => 12]);
}

Node.js (bcryptjs)

import bcrypt from 'bcryptjs';

// Create hash
const hash = await bcrypt.hash(password, 12);

// Verify password
const isCorrect = await bcrypt.compare(password, hash);

Python (bcrypt)

import bcrypt

# Create hash
hash = bcrypt.hashpw(password.encode(), bcrypt.gensalt(rounds=12))

# Verify password
is_correct = bcrypt.checkpw(password.encode(), hash)

Typical use cases for the bcrypt generator

• Development & testing: Generate test hashes for database seeds, fixtures and automated tests
• Admin accounts: Insert a password hash for a new user directly into the database via SQL
• Debugging: Check whether a stored hash really matches the expected password
• Migration: Validate hashes in advance when switching from MD5/SHA to bcrypt
• Learning & understanding: Follow the structure of bcrypt hashes and the effect of the cost factor live

Create bcrypt hashes in three steps