Welcome the Technical Support section. Help us in assisting you by providing us with a concise and descriptive elaboration of your issues. Be specific and if possible, provide us with a step-by-step instruction in replicating your problem.
I am sorry this is not possible, you cant change the password encyription, but even it possible I am afraid it won't work smoothly with another component like Jomsocial.
If you need better answer I suggest you post your question to Joomla forum,