Password hash that can be upgraded without plaintext password Most password hashes have a cost parameter that indicates how long the algorithm should take. Is there an algorithm where you can increase that cost for a particular hash, without access to the plaintext password?

So I have existing hashes in the database with cost=10, and I want to upgrade these to cost=20, without access to the plaintext password.

This isn't possible for PBKDF2 and bcrypt, because these use the password in each iteration. Is there any algorithm that supports this? Is there a specific name for this property?
This is called Client-Independent Update, according to the 
Catena paper.


  It is desirable to be able to compute a new password hash (with some higher security parameter) from the old one (with the old and weaker security parameter), without having to involve user interaction, i.e.,
  without having to know the password. We call this feature a client-independent update of the password hash.


The Rig password hash adopted this term:


  Client-independent update: Our design supports client independent
  update, i.e., server can increase the security parameter without knowing the password.


This article even shorts it to CIU. 


Battcrypt and Parallel have CIU or are easily modified to have it.
POMELO mentions that you could just run the algorithm twice to get CIU.
Yescrypt seems to have CIU.


An overview: