Reference for the current password hashing algorithms in FusionAuth
Overview
FusionAuth provides several options for Password Encryption schemes.
An ideal password hashing algorithm should be slow. When hashing is fast and password entropy is low, brute force attacks become a high risk. Even with enforced password policies, low password entropy can be difficult to mitigate. Choosing a slow algorithm is actually preferred for password hashing. Of the hashing schemes provided, only PBKDF2 and Bcrypt are designed to be slow which makes them the best choice for password hashing, MD5 and SHA-256 were designed to be fast and as such this makes them a less than ideal choice.
When selecting a load factor for the hashing scheme, the minimum values are provided for a starting guideline only. The factor should be set as high as possible such that the login times are still acceptable to your end users. Be cautious with setting the factor too high, especially with Bcrypt, setting the factor too high may cause login requests to take seconds or minutes to complete.
Salted MD5
MD5 is a general purpose hashing algorithm producing a 128-bit hash. This is weak hash that has been shown to be compromised and is vulnerable to brute force attacks. This hash is provided for migration purposes and it should be upgraded to a stronger hash as soon as possible. A recommended minimum factor for this hashing algorithm is 20,000.
Salted SHA-256
SHA-256 is part of the SHA-2 set of cryptographic standards. SHA-256 is a general purpose hash and similar to MD5 it was designed to be fast which makes it a less than ideal choice for a password hashing. This hash is mainly provided for migration purposes or where login performance is very critical. If login performance has not become an issue a stronger scheme should be utilized. A recommended minimum factor for this hashing algorithm is 20,000.
Salted HMAC SHA-256
HMAC SHA-256 is a hash based message authentication code. This scheme is still vulnerable to brute force attacks and like MD5 and SHA-256 is mainly provided for migration purposes or where login performance is very critical. If login performance has not become an issue a stronger scheme should be utilized. This scheme does not utilize a factor.
Salted PBKDF2 HMAC SHA-256
PBKDF2 (Password-Based Key Derivation Function2) applies a hash-based message authentication code (HMAC) to the salted input and iterates based upon a factor to produce the hashed output. A recommended factor for this hashing algorithm is between 5,000 and 100,000 depending on the CPU performance of your system.
Salted Bcrypt
Bcrypt is a password hashing function based on the Blowfish cipher. A recommended factor for this hashing algorithm is between 8 and 14. Unlike the other mentioned hashing functions the factor for Bcrypt is not simply an iteration count. Bcrypt uses the factor as a work factor, the work factor will be calculated using the provided factor as power of 2. This means that the difference between a factor of 12 and 13 is 2x. For example 2^12 = 4096 and 2^13 = 8192.