Specifications

SSH — Secure Shell, the Safe Alternative
In these times of increasing networks, accessing a remote system also be-
comes more common. Regardless of the activity, the person accessing the
system must be authenticated.
Most users should know by now that the user name and password are only
intended for individual use. Strict confidence pertaining to personal data
is usually guaranteed between the employer, computer center, or service
provider. However, the ongoing practice of authenticating and transferring
data in clear text form is a frightening phenomenon. Most directly affected
are the commonly used services Post Office Protocol (POP) for retrieving mail
and telnet for logging in on remote systems. Using these methods, user in-
formation and data considered sensitive, such as the contents of a letter or a
chat via the talk command, travel openly and unsecured over the network.
This encroaches on the user’s privacy and leaves such access methods open
to misuse. Usually, this misuse occurs by accessing one system to attack an-
other or to obtain administrator or root permissions.
Any device involved in data transfer or operating on the local network, such
as firewall, router, switch, mail servers, or workstations, can also access the
data. There are laws prohibiting such behavior, but it is difficult to detect.
The SSH software provides the necessary protection. Complete authentication,
usually user name and password, as well as the communication is encrypted.
Even here, snatching the transferred data is possible, but the contents cannot
be deciphered by intruders without the key. This enables secure communi-
cation via unsafe networks, such as the Internet. SuSE Linux, provides the
package OpenSSH.
The OpenSSH Package
SuSE Linux installs the package OpenSSH by default. The programs ssh, scp,
and sftp will thus be available as alternatives to telnet, rlogin, rsh, rcp, and
ftp.
The ssh Program
Using the ssh program, it is possible to log in to remote systems and work
interactively. It replaces both telnet and rlogin. The symbolic name slogin
points to ssh. For example, it is possible to log in to the host sun with the
command ssh sun. The host then prompts for the password on sun.
190 SSH — Secure Shell, the Safe Alternative