↳ In-reply-to » I made a thing. Its a multi password type checker. Using the PHC string format we can identify a password hashing format from the prefix $name$ and then dispatch the hashing or checking to its specific format.

Circling back to the IsPreferred method. A hasher can define its own IsPreferred method that will be called to check if the current hash meets the complexity requirements. This is good for updating the password hashes to be more secure over time.

func (p *Passwd) IsPreferred(hash string) bool {
	_, algo := p.getAlgo(hash)
	if algo != nil && algo == p.d {

		// if the algorithm defines its own check for preference.
		if ck, ok := algo.(interface{ IsPreferred(string) bool }); ok {
			return ck.IsPreferred(hash)
		}

		return true
	}
	return false
}

https://github.com/sour-is/go-passwd/blob/main/passwd.go#L62-L74

example: https://github.com/sour-is/go-passwd/blob/main/pkg/argon2/argon2.go#L104-L133