TCP/IP Tutorial and Technical Overview - IBM Redbooks

architecture still allows proxies to exist between client and servers. In such a
scenario, the process of setting up end-to-end TLS capabilities becomes more
complicated. The OMA WAP-219-TLS-20010411-a specification addresses this
by defining the process of creating a TLS tunnel across a proxy.
In such a scenario, the proxy server acts only as a transport layer data relay,
performing no processing on messages passed between the server and client,
nor passing the message up to higher layers in the architecture. This is illustrated
in Figure 18-22.
WAP client WAP server
Upper
Layers
TLS
Transport
and IP
Layers
Wireless
Transport
and IP
Layers
Figure 18-22 An example of TLS tunnelling
18.10.2 Wireless Identity Module (WIM)
WAP proxy
Transport
and IP
Layers
Wireless Wireless
Upper
Layers
TLS
Transport
and IP
Layers
Wireless
In implementing WTLS, it is important to have a tamper-proof device that stores
secret information (such as keys and certificates) and can also perform other
security functions (such as cryptology). Such a device increases the difficulty
faced by a malicious user attempting to gain access to such information. In order
to achieve this functionality, WAP2 architecture defines the Wireless Identity
Module (WIM). This typically exists as a smart card within the mobile device.
Defined originally by the OMA WAP-260-WIM-20010712-a specification, the
Chapter 18. Wireless Application Protocol 701