Bcrypt Hashing vs Encryption: What Is the Difference?
Understand why passwords should be hashed with a password-specific algorithm such as bcrypt instead of encrypted and later decrypted.
Hashing and encryption solve different problems. Encryption is designed to protect data that must eventually be recovered with a key. Password hashing is designed to make verification possible without storing the original password. This distinction is fundamental to application security.
What is a hash?
A cryptographic hash transforms input into a fixed-format digest. A good password hashing algorithm also incorporates a salt and a configurable work factor so that guessing passwords becomes expensive. Bcrypt is designed specifically for this kind of password storage.
Why passwords should not be encrypted
If an application can decrypt every stored password, an attacker who obtains the decryption key may be able to recover every password. Password verification does not require that capability. The application only needs to determine whether a submitted password matches the stored password hash.
How bcrypt verification works
During registration, the application hashes the password and stores the resulting bcrypt string. During login, it runs the submitted password through the verification function against that stored value. The original password is never recovered from the hash.
What developers should avoid
- Do not store plaintext passwords.
- Do not use MD5 or SHA-1 as a password hashing algorithm.
- Do not invent your own password hashing scheme.
- Do not compare password hashes by decrypting them.
- Use the password-hashing APIs provided by your framework.
Where bcrypt fits today
Bcrypt remains a practical password hashing option and is widely supported. Modern applications should also consider the password hashing options recommended by their current framework and security guidance. The key principle is to use a password-specific, adaptive algorithm rather than a general-purpose checksum.
Frequently asked questions
Can bcrypt be decrypted?
No. Bcrypt is a one-way password hashing algorithm. Verification is performed by checking a candidate password against the stored hash.
Is bcrypt the same as encryption?
No. Encryption is reversible with the appropriate key. Password hashing is intentionally not reversible.
Can I use MD5 for passwords?
No. MD5 is fast and unsuitable for protecting passwords against modern password-guessing attacks.