How to Store Passwords: Salting, Slow Hashing, and bcrypt's Three Lines of Defense

The correct answer for password storage: a "slow hash with automatic salting" algorithm like bcrypt, scrypt, or argon2. Any fast general-purpose hash (the MD5/SHA family) fails the test — even with a salt. Use our random password generator to create high-strength passwords.

The three lines of defense

Defense one: never store plaintext. Database breaches are a matter of probability, not hypotheticals. Plaintext storage leaks every user's password directly — and because people reuse passwords across sites, the blast radius multiplies.

Defense two: add hashing. Hashes are irreversible, but general-purpose hashes are far too fast — a consumer GPU can compute tens of billions of MD5 hashes per second, so a dictionary of common passwords plus brute force finishes quickly.

Defense three: slow hashing + salt.

• Salt: hash each password together with a random value so identical passwords produce different hashes, defeating rainbow tables and batch cracking. The salt doesn't need secrecy — store it alongside the hash.
• Slowness (work factor): bcrypt's cost parameter stretches each computation to a controlled duration (e.g. 100ms). Users won't notice at login, but an attacker's enumeration cost is amplified a hundred-million-fold. As hardware improves, just raise the cost.

Comparison table

Approach	Resists rainbow tables	Resists GPU brute force	Verdict
Plaintext	❌	❌	Forbidden
MD5(password)	❌	❌	Forbidden
SHA-256(salt+password)	✅	❌ (too fast)	Inadequate
bcrypt / argon2	✅	✅	The standard answer

The complete pipeline

• Transport relies on HTTPS — don't hash on the client before sending; that turns the hash itself into a "password equivalent."
• Leave room in the storage column: bcrypt output is a fixed 60 characters, but argon2's PHC string is longer — VARCHAR(255) is a safe choice.
• Don't distinguish "user not found" from "wrong password" in login errors, or attackers can enumerate valid accounts.
• Add CAPTCHAs and rate limiting to block online credential stuffing.

Last updated: 2026-09-08