Sensible Doctrine Expression and Zend_Auth setCredentialTreatment()

How to create reasonable expression to store password in database using Doctrine and Zend_Auth::setCredentialTreatment()?

I don't want to use md5() and the code must be portable, and with salt.

I would call this not easy one to guess:

setCredentialTreatment("SHA1(CONCAT(username, SHA1(CONCAT(username, ?)))");

but it is not portable to all databases.

Seems that Doctrine_Expression has only 开发者_如何学Gomd5 expression portability.

Why not write your own Zend_Auth_Adapter?