The Symbian OS security architecture fundamentally consists of two high level components:
Cryptography
Together these modules/components form the basis of a number of higher level components, which include:
Certificate management control panel item (UI to certificate management allowing control of trusted root certificates)
Software installation (authentication/digital signatures)
Secure comms (SSL/TLS, WTLS, IPSec, etc.)
Diagram
The following diagram shows the dependencies beween components in the Security architecture, and the names of each component's executables: