Public-key authentication is based on the use of digital signatures. Each user creates a pair of key files. One of these key files is the user's public key, and the other is the user's private key. The server knows the user's public key, and only the user has the private key.

The key files must be stored to a location where the user has the write rights, (and read rights), but that is not accessible to others. These user-specific rights are required for the key.pub file, the authorized_keys directory, and to the authorization file, if used.

When the user tries to authenticate, the client sends a signature to the server, and the server checks for matching public keys. If the key is protected with a passphrase, the server requests the user to enter the passphrase.

	Caution
	Do not store your private keys in a location accessible to other users.

To use public-key authentication with SSH Tectia client tools for z/OS, do the following actions:

For instructions on using public-key authentication to connect from other hosts to SSH Tectia Server for IBM z/OS, see Using Public-Key Authentication from Other Hosts to z/OS.

In the following instructions, Server is the remote host running the Secure Shell server that you are trying to connect to. ServerUser is the username on Server that you are logging in as. Client is the host running the Secure Shell client (SSH Tectia client tools for z/OS). ClientUser is the username on Client that should be allowed to log in to Server as ServerUser. See Figure 4.2.

Figure 4.2. User public-key authentication

The instructions assume that ClientUser is allowed to log in to Server as ServerUser using some other authentication method (usually password).