arcor/vodafone won't give you your sip password for free, but i will: capture an incoming call (WAN VC2) with the diagnostic tool in your easybox, load the .cap file in wireshark and search for SIP/SDP Request:INVITE, Message Header -> Proxy-Authorization

easybox_sip_passwd.pl

#!/usr/bin/env perl
use strict;
use warnings;
use Digest::MD5 'md5_hex';

print_usage() unless($#ARGV==5);

my ($method, $uri, $user, $realm, $nonce, $response) = @ARGV;
my $hash_method_uri = md5_hex(join(':', $method, $uri));

my $passwd = 0;
while($passwd < 100000000) { # arcor/vodafone sip passwords consists of 8 digets
  my $calc_response = md5_hex(join(':',
                                   md5_hex(join(':',
                                                $user,
                                                $realm,
                                                $passwd)),
                                   $nonce,
                                   $hash_method_uri));
  if($calc_response eq $response) {
    print "password found: $passwd\n";
    exit;
  }
  $passwd++;
}
print "password not found :-(\n";

sub print_usage {
  print <<"USAGE";
./$0 <method> <uri> <user> <realm> <nonce> <response>

./$0 INVITE sip:12345\@bar.baz 0123456789 bar.baz 1234567890abcdef1234567890abcdef12345678 1234567890abcdef1234567890abcdef
USAGE
  exit;
}