Siemens Version: 1.2 User Manual

3. Security Analysis

The MiniWeb server is well implemented. The SSL implementation does not show

any failures. The only security weakness is the long life span of the certificate and

the use of MD5 for the generation of the certificates. The key length of 1024 bits is

sufficient for the next three to five years.

3.1.6 Time Synchronization and Logging

The security module allows time synchronization based on the (simple-)network-

time-protocol (NTP). The NTP protocol is an UDP protocol. The client requests the

time from an NTP server and the server responds with its current time. Since the

UDP protocol is used, the NTP protocol does not offer any protection against IP

spoofing or data manipulation.

The NTP protocol neither provides authenticity nor integrity of the transferred time.

A forgery of the information allows a denial-of-service-attack (DoS) on the VPN

function. Hence, the NTP protocol should be used cautiously.

The logging of the time setting shows weaknesses since expired certificates and

ARP spoofing attacks are not logged. Even the failure of establishing IPsec tunnels

due to the expired certificates were not logged. A modification of the time is logged

only when this is set manually, but not when it is set over NTP. In the default

setting numerous events are not logged.

3.2 Configuration

The security module is configured by means of a security configuration tool

installed on the configuration PC. This tool stores its files encrypted in a database.

The configuration data is transferred from the PC to the security module in an

encrypted manner with SSL. During the first configuration at initialization time a

direct connection between PC and security module is necessary since the

addressing of the security module is made via the MAC address. Afterwards, the

communication is carried out over IP such that no direct connection is required

anymore for configuring the Scalance device. Certificates and keys are then

transferred to the security module by the configuration tool.

It was not possible to break the encryption of the configuration files. A man-in-the-

middle attack on the encrypted SSL transfer is not possible. Since no further

access to the security module is available, the communication channel between

configuration PC and security module is secure.

19-Aug-05 escrypt

GmbH