As the size and popularity of the Internet has grown, so has the threat of communication interception. Over the years, tools have been developed to encrypt communications as they are transferred over the network.
Red Hat Enterprise Linux ships with two basic tools that use high-level, public-key-cryptography-based encryption algorithms to protect information as it travels over the network.
OpenSSH — A free implementation of the SSH protocol for encrypting network communication.
Gnu Privacy Guard (GPG) — A free implementation of the PGP (Pretty Good Privacy) encryption application for encrypting data.
OpenSSH is a safer way to access a remote machine and replaces older, unencrypted services like telnet and rsh. OpenSSH includes a network service called sshd and three command line client applications:
ssh — A secure remote console access client.
scp — A secure remote copy command.
sftp — A secure pseudo-ftp client that allows interactive file transfer sessions.
It is highly recommended that any remote communication with Linux systems occur using the SSH protocol. For more information about OpenSSH, refer to the chapter titled OpenSSH in the Red Hat Enterprise Linux System Administration Guide. For more information about the SSH Protocol, refer to the chapter titled SSH Protocol in the Red Hat Enterprise Linux Reference Guide.
Although the sshd service is inherently secure, the service must be kept up-to-date to prevent security threats. Refer to Chapter 3 Security Updates for more information about this issue.
GPG is one way to ensure private email communication. It can be used both to email sensitive data over public networks and to protect sensitive data on hard drives.
For more information about using GPG, refer to the appendix titled Getting Started with Gnu Privacy Guard in the Red Hat Enterprise Linux Step By Step Guide.