Security & Crypto

Bcrypt Hash Generator & Verifier

Generate bcrypt password hashes at the cost you choose, or verify a hash against a password. Everything runs locally in your browser.

Algorithm

bcrypt

Adaptive, salted, designed for password storage.

Cost

≈ 400 ms per hash on a modern laptop.

Mode

Generate

Switch tabs to hash a password or check a stored hash.

Workspace

Type a password, pick a cost factor, and generate a salted bcrypt hash. The salt is random unless you opt into a custom one.

Password

Very weak0 bits · ≈ instantly to brute-force

Cost (work factor)12

Range 4-15. OWASP minimum is 10. Cost doubles per increment — currently ≈ 400 ms.

Salt

A fresh 16-byte salt is generated for every hash. Recommended.

Cost vs. time

Rough wall-clock estimates per hash. Real numbers depend on the device.

CostWork (2ⁿ iterations)≈ time

416 iterations2 ms

8256 iterations25 ms

101,024 iterations100 ms

12current4,096 iterations400 ms

1416,384 iterations1.6 s

1665,536 iterations3.2 s

Anchored at cost 10 ≈ 100ms on a modern laptop. Work doubles per +1 cost. Mobile and serverless cold-starts can be 3-5× slower.

What is bcrypt?

Bcrypt is an adaptive password-hashing function based on Blowfish. It bundles a per-password salt and a tunable work factor inside the hash itself, so verification just needs the hash and the password.

Cost = work factor

Each +1 to cost doubles the number of iterations. Pick the highest cost your login flow can tolerate (~200-400ms is the sweet spot). Re-hash on login when you raise it.

Why bcrypt over MD5/SHA-256?

MD5 and raw SHA-256 are fast — a GPU bruteforces billions per second.
Bcrypt is deliberately slow and memory-bound enough to resist GPU/ASIC attacks.
Every hash carries its own salt, so identical passwords never look identical.
Cost is tunable, letting you keep up with hardware over time.

72-byte truncation gotcha

Bcrypt silently truncates passwords longer than 72 UTF-8 bytes. If you allow long passphrases, pre-hash with SHA-256 and feed the hex digest to bcrypt to keep the full entropy.

Modern alternatives

argon2id and scrypt are the OWASP picks for new systems — they add memory hardness on top of CPU cost. Stick with bcrypt when interoperating with existing stores or libraries.