function doChallengeResponse(prefix)
{
	var app_email = eval('document.loginForm.'+prefix+'email.value.toLowerCase();');
	var app_password = eval('document.loginForm.'+prefix+'password.value;');
	var challenge = document.loginForm.challenge.value;
	
	var str = app_email + sha256_digest(app_password) + challenge;
	document.loginForm.response.value = sha256_digest(str);
	
	eval('document.loginForm.'+prefix+'password.value = ""');
	document.loginForm.challenge.value = "";
	
	return false;
}