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Bcrypt vs SHA-256 Comparison
Compare Bcrypt vs SHA-256 for password security: adaptive work factor, built-in salting, GPU resistance, and hash calculation tools.
Updated 2026-09-07
Side-by-side comparison
| Factor | BCRYPT | SHA256 |
|---|---|---|
| design_purpose | Slow, adaptive key derivation specifically for password hashing | Fast cryptographic digest for file integrity and digital signatures |
| work_factor_cost | Configurable logarithmic cost (2^N rounds) adjustable over time | Fixed, single-pass computation that cannot be slowed down |
| built_in_salt | Automatically generates and stores a 128-bit random salt | No salt mechanism; developers must manually salt or risk rainbow tables |
| gpu_asic_resistance | Memory-intensive Blowfish setup that cripples GPU parallel attacks | Massively parallelizable on modern GPUs (billions of hashes/sec) |
| output_format | Modular Crypt Format ($2a$, $2b$) containing cost, salt, and hash | 64-character raw hexadecimal string |
| password_security | Industry standard and recommended by OWASP for credential storage | Insecure for storing passwords, even when salted |
When to use which
- User password storage and authentication databases: BCRYPT
- File integrity verification and git commit hashes: SHA256
- High-speed API request signing and HMAC verification: SHA256
- Brute-force resistant credential storage: BCRYPT
FAQ
- Why is plain SHA-256 dangerous for storing user passwords?
- SHA-256 is designed to be fast and compute-efficient for data integrity. On modern consumer GPUs (like an NVIDIA RTX 4090), an attacker can compute tens of billions of SHA-256 hashes every second, cracking typical human passwords via brute-force or dictionary attacks in minutes.
- How does Bcrypt prevent GPU brute-force attacks?
- Bcrypt uses a key setup algorithm based on Blowfish that requires 4 KB of tightly bound memory and frequent memory accesses. GPUs cannot parallelize memory-intensive algorithms efficiently, reducing cracking speed from billions of hashes per second to just dozens.
- Does adding a salt make SHA-256 secure for passwords?
- No. Salting prevents attackers from using precomputed rainbow tables across multiple users, but it does nothing to slow down targeted GPU brute-force guessing against an individual salted hash. Password hashes must be computationally expensive.
- What is an appropriate work factor for Bcrypt?
- OWASP recommends a cost factor of at least 10 or 12 in production environments. This targets a verification time of approximately 250 to 350 milliseconds per authentication attempt on modern server hardware.