Linux and Open-Source Applications

The building blocks for a secure and trustworthy computer platform.
Banks of Trustworthy Software

Of course, getting users to carry out this certification process would be impossible. What is really needed is a system of software repositories—or “banks”--from which users can obtain certified versions of Linux and associated applications.

A national organization, such as the U.S. National Security Agency, could verify open-source programs and place both source and binaries on the Web for immediate download. However, this approach would be subject to the same concerns that make closed-source software insecure. A disgruntled employee could add some extras to the certified code, or perhaps a government organization will decide that having a back-door might be useful for national security reasons.

Clearly, no single testing organization can be trusted. A better approach would be to have three or more certification organizations, each with its own download site. The National Security Agency in the U.S., the Communications-Electronics Security Group in Britain and the Communications Security Establishment in Canada could each independently verify and make certified binaries available. A user could then download the same binaries from all three sites and be sure they are trustworthy if, and only if, no differences are found. While there is a potential security problem in downloading over the Internet (after all, a devious ISP could intercept the FTP request and divert it to a rigged server), the likelihood of that is small and the chances of it being discovered are high.

For even greater security, each of the major certifying sites would also make certified CD-ROMs available, preferably each with a simple file-comparison program directly bootable from the unalterable CD. That way, one could order certified CDs from two or more certifying agencies and do a quick file comparison between them as a final verification. The write-only nature of CDs would also prevent any corruption on one from contaminating the other CDs.

Of course, trusting the U.S., Britain and Canada's electronic espionage agencies might leave something to be desired. By requiring each certifying agency to make not only its certified binaries available but also the original source code, it would be possible for other countries, companies or individuals to set up their own complementary certifying sites. Presumably, millions of Internet users would be continuously watching the various sites offering certified applications and operating systems, and a sudden discrepancy at one of them would be noticed, investigated and exposed. By having each certification organization keep its own set of confidential source-code examples for testing the output of compilers being certified, one could dramatically reduce the already small chance of a clever compiler recognizing test code and producing sanitized executables during certification.

At this point, it is also worth emphasizing that a proliferation of independent certifying sites for open-source software located around the world would not only be an excellent safeguard against any sort of Easter egg or back door, but would also ensure that bugs—particularly the security-sensitive ones—are exposed and quickly corrected.

Conclusions

There are potentially severe security problems arising from the inherent nature of closed-source software and its use on Internet-connected computers. While the chances of someone planting a globally or even nationally destructive section of code in a popular operating system or application program is low, the consequences of such an event are potentially too disastrous to ignore. Indeed, a well-orchestrated Easter-egg attack could make the Y2K problem look miniscule in comparison. To safeguard against these problems, the solution is the replacement of closed-source applications and operating systems with certified open-source programs. Organizations providing banks of certified trusted applications and operating systems could provide a vital public service.

Resources

Peter F. Jones is a research engineer at Neptec Communications in Ottawa, Canada. He received a B.Sc. (1986) and a Ph.D. (1993) from the Department of Electrical Engineering at Queens University, Kingston, Ontario, Canada and is also a licensed engineer (P.Eng). Peter has worked on a variety of software projects including writing SVGA card graphics drivers, creating a Java web search engine, and developing a Linux-based multiple-sound card interface library for an adaptive antenna phased-array HF modem. He is currently working on two projects: developing a miniature single-board Linux computer for home and office applications and studying the characteristics of the Space Shuttle's TV cameras for the purposes of developing algorithms to reduce image distortions. Peter can be reached via e-mail at pjones@neptec.com.

Mark B. Jorgenson is at Neptec Communications in Ottawa, Canada. His B.Sc. (1984) and M.Sc. (1989) are both in Electrical Engineering from the University of Calgary and he is also a licensed engineer (P.Eng). Mark's main research focus is in wireless communications, with emphasis on link-layer aspects. Mark has recently led the development of a software radio prototype and is currently leading a team designing an advanced HF radio modem. He can be reached via e-mail at mjorgenson@neptec.com.

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