Defines the password hashers used by the application.

Sometimes it's needed to change the password hashing algorithm, because of a better algorithm or some similar case. But the passwords stored in the backing store cannot easily be converted with another algorithm because they're hashed and cannot be decrypted back to plain text. For such case Silhouette supports the change of hashing algorithms on the fly. So if a user successfully authenticates after the application has changed the hashing algorithm, the provider hashes the entered plain-text password again with the new algorithm and overrides the auth info in the backing store with the new hash.

The password hasher registry defines the current password hasher which is able to hash all new passwords and also match the passwords stored in the backing store for this algorithm. And also a list of deprecated hashers, which should match passwords that are stored in the baking store but which are different to the current hasher.