SSH, The Secure Shell: The Definitive Guide, 2nd Edition

Chapter 6. Key Management and Agents

Your SSH private key is a precious thing. When you use public-key authentication, your key proves your identity to SSH servers. We’ve encountered several programs related to keys:

ssh-keygen

Creates key pairs

ssh-agent

Holds private keys in memory, saving you from typing your passphrase repeatedly

ssh-add

Loads private keys into the agent

However, we haven’t gone into much depth, covering only the most basic operations with keys. Now it’s time to examine these concepts and programs in detail.

We begin with an overview of SSH identities and the keys that represent them. After that, we thoroughly cover SSH agents and their many features. Finally, we extol the virtues of having multiple SSH identities. If you’ve been getting by with a single key and only light agent use, we have a lot of cool stuff in store for you. Figure 6-1 summarizes the role of key management in the overall configuration process.

This chapter is the first in a sequence on advanced SSH for end users, as opposed to system administrators. Once you’ve covered key management in this chapter, we’ll take you through client configuration, server configuration, and forwarding in Chapters 7-9.