3.3. The Architecture of an SSH SystemSSH has about a dozen distinct, interacting components that produce the features we've covered. [Section 3.1, "Overview of Features"] Figure 3-1 illustrates the major components and their relationships to one another.
Figure 3-1. SSH architectureBy "component" we don't necessarily mean "program:" SSH also has keys, sessions, and other fun things. In this section we provide a brief overview of all the components, so you can begin to get the big picture of SSH:
Table 3-1. Keys, Keys, Keys
TIP: SSH-1 uses a single session key, but SSH-2 has several: each direction (server to client, and client to server) has keys for encryption and others for integrity checking. In our discussions we treat all SSH-2's session keys as a unit and speak of "the session key" for convenience. If the context requires it, we specify which individual key we mean.
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