Changes in felogin-Template:

Within subpart <!--###TEMPLATE_LOGIN###--> ... <!--###TEMPLATE_LOGIN###-->

change line
<form action="###ACTION_URI###" target="_top" method="post" onsubmit="###ON_SUBMIT###">
to 
<form action="###ACTION_URI###" target="_top" method="post" onsubmit="copyPassword(this);">


change lines 
<label for="pass">###PASSWORD_LABEL###</label>
<input type="password" id="pass" name="pass" value="" />
to 
<label for="pass_temp">###PASSWORD_LABEL###</label>
<input type="password" id="pass_temp" name="pass_temp" value="" />


add line
<input type="hidden" name="pass" id="pass" value="" />


Add the following javascript:

function copyPassword(login_form){
	jQuery('#pass').val(jQuery('#pass_temp').val()); //copy the entered clear text password into the hidden field
	jQuery('#pass_temp').val('');	//set clear text password to an empty string
	tx_rsaauth_feencrypt(login_form);	call rsa function, that takes care of encrypting the password
}