This is a cryptographic tool that uses public-key techniques (RSA) for setting up each connection session. The encryption during each session uses private-key methods (IDEA by default).

SSH is not open source and is becoming less free as it evolves. However, it is free for personal use and the source code is available. While the current version is 2.0, many people are staying with version 1.2.x since its licensing is more generous and it provides what you need.

On any Linux-based system better than a 486, the overhead of encrypting the terminal session in real time is hardly perceptible. Even on faster computers, however, there is a noticeable delay (3 to 12 seconds) while the session key is negotiated.

SSH has some tricks up its sleeve with regard to tunnelling, which can secure GUI-based and text-based programs. Without SSH, starting a program that uses the X Window System (an X client) requires manually setting DISPLAY settings, and X is not a secure protocol. With SSH, however, the X client's traffic can be forwarded through the secure channel established for the terminal connection -- a nice bonus.

It provides a high-level language, backward compatible with Matlab, for mathematical computations. There is a large archive of contributed functions based on Octave at ftp://ftp.ci.tuwien.ac.at/pub/octave/octave-ci.tar.gz.

Octave is capable of generating sophisticated 3D and 2D graphs using the GNUplot package (see below).

Although it was initially conceived as a teaching aid for chemical engineering, after about a decade of development, Octave has well and truly matured beyond the educators' toy. It's a 'workhorse' application for those needing such a tool, and is widely used in teaching, research and engineering.

It has great flexibility and lends itself to both powerful interactive use and embedding within a script or program. It has a good facility for hard copy output by generating PostScript files.

GNUplot has been around for quite a long time, and comes with Red Hat Linux (and possibly other distributions), so we include it in the 'unsung hero' category.

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