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Replacing Telnet; OpenSSH, a secure alternative

The Internet is built with communication in mind. You will routinely move

around the Web from one site to the other or telnet to another machine to

check your mail or to administer that machine. The trouble with most of

these protocols is that they are not encrypted. Over a telnet connection,

your passwords are sent as plain-text, which can be read by anyone.

Using sophisticated programs called packet sniffers, even a amateur hacker

can spy on your connection and grab your data.

Secure Shell (SSH) was built to address these faults and provide a more

secure environment to work in. SSH encrypts all your traffic including

your passwords when you connect to another machine over the net. SSH also

replaces telnet, ftp, rsh, rlogin and rexec.

Let's take a look at OpenSSH, an excellent and more importantly open

source implementation of SSH. It is very well supported by the OpenBSD

team and includes rock-solid SSH2 support. Versions are available for

nearly all the Unices including Linux, which is what we are using here.

OpenSSH can be downloaded from www.openssh.com. The latest version as of

writing this article is 2.3.0. It is available as source tarballs

or in RPM format. If you are downloading the RPM's, then you need to get

the following files.




Zlib - This is an open source and patent free lossless data compression

library. This should already have been installed as part of your standard

Linux installation. If not then you can download it from

http://www.freesoftware.com/pub/infozip/zlib/. Source is available as

also RPMs. Take your pick.

OpenSSL - Another open source effort, aimed at creating a commercial grade

toolkit implementing Secure Socket Layer (SSL), Transport Layer Security

(TLS) and a strong cryptography library. This is also available as source

or RPM packages. The RPM packages are available right where the OpenSSH

RPMs are. The source packages are available at www.openssl.org



RPM: rpm -ivh zlib-1.1.3-i386.rpm

For the tar.gz

tar zxvf zlib-1.1.3.tar.gz

cd zlib-1.1.3



su -c "make install"


RPM: rpm -ivh openssl-0.9.5a-i386.rpm

For the tar.gz