IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Hardware & Software Remarks
____________________________________________________________________ .........................................
that is generated implicitly during the exchange of information (such as traffic
flow information).
Security relationships may exist for various security services on various OSI
layers simultaneously. Above the layer on which a security service is
implemented, the information (relating to that service) is not secured.
Cryptographic mechanisms (encryption, digital signature, cryptographic
checksums) contribute to the implementation of important security services
(authenticity, confidentiality, integrity, verification of communication and
verification of the origin of data).
First let us look at an overview of the criteria that speak for or against the use
of cryptographic procedures on the various OSI layers:
____________________________________________________________________ .........................................
IT-Baseline Protection Manual: Oktober 2000
Use of cryptographic procedures on
higher layers: lower layers:
+: Makes sense if the application
data is to be protected close to the
application or if the "insecure
channel" is to be kept as short as
possible
+: Whenever the data is not
protected on the lower layers
+: Makes sense if there are a large
number of changing
communication partners at various
locations
+: Users can make use of them in
accordance with their own
requirements
+: Security is provided closer to the
user, and is more easily
recognisable by him
-: Undermines safeguarding by
firewalls
-: Often subject to operating errors
-: Often based on software;
cryptographic keys and algorithms
are easier to manipulate
-: Greater dependency on the
operating system or on underlying
hardware
+: Makes sense for the coupling of
two networks that are classed as
secure via an insecure
connection, e.g. linking two
properties via public networks
+: For securing a network against
unauthorised access
+: Whenever traffic flow
information needs to be
protected, e.g. address
information
+: All higher-level header
information and the user
information is encrypted
+: Transparent for users, relatively
low risk of operating error
+: Easier key management
-: Protection only as far as the layer
in which the security protocols
are implemented
-: Often hardware, i.e. expensive
and inflexible
-: Often does not offer end-to-end
security
Simple key management procedures are generally obtained if group keys can
be used, for example when setting up secure subnetworks (VPNs) in which the
access ports are equipped with cryptographic devices.
The purchase price of cryptographic products for the lower layers is usually
considerably higher than that of those for higher layers, but it also has to be