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FreeS/WAN: Securing the Internet against Wiretapping

by John Gilmore <>, 1999

My project for 1996 was to secure 5% of the Internet traffic against passive wiretapping. It didn't happen in 1996, so I'm still working on it in 1999! If we get 5% in 1999 or 2000, we can secure 20% the next year, against both active and passive attacks; and 80% the following year. Soon the whole Internet will be private and secure. The project is called S/WAN or S/Wan or Swan for Secure Wide Area Network; since it's free software, we call it FreeS/WAN to distinguish it from various commercial implementations. RSA came up with the term "S/WAN". Our main web site is at Want to help?

The idea is to deploy PC-based boxes that will sit between your local area network and the Internet (near your firewall or router) which opportunistically encrypt your Internet packets. Whenever you talk to a machine (like a Web site) that doesn't support encryption, your traffic goes out "in the clear" as usual. Whenever you connect to a machine that does support this kind of encryption, this box automatically encrypts all your packets, and decrypts the ones that come in. In effect, each packet gets put into an "envelope" on one side of the net, and removed from the envelope when it reaches its destination. This works for all kinds of Internet traffic, including Web access, Telnet, FTP, email, IRC, Usenet, etc.

The encryption boxes are standard PC's that use freely available Linux software that you can download over the Internet, or install from a cheap CDROM.

This wasn't just my idea; lots of people have been working on it for years. The encryption protocols for these boxes are called IPSEC (IP Security). They have been developed by the IP Security Working Group of the Internet Engineering Task Force, and will be a standard part of the next major version of the Internet protocols (IPv6). For today's (IP version 4) Internet, they are an option.

The Internet Architecture Board and Internet Engineering Steering Group have taken a strong stand that the Internet should use powerful encryption to provide security and privacy. I think these protocols are the best chance to do that, because they can be deployed very easily, without changing your hardware or software or retraining your users. They offer the best security we know how to build, using the Triple-DES, RSA, and Diffie-Hellman algorithms.

This "opportunistic encryption box" offers the "fax effect". As each person installs one for their own use, it becomes more valuable for their neighbors to install one too, because there's one more person to use it with. The software automatically notices each newly installed box, and doesn't require a network administrator to reconfigure it. Instead of "virtual private networks" we have a "REAL private network"; we add privacy to the real network instead of layering a manually-maintained virtual network on top of an insecure Internet.


The US government would like to control the deployment of IP Security with its crypto export laws (warning: may be censored for Internet "Free Speech" violations). This isn't a problem for my effort, because the cryptographic work is happening outside the United States. A foreign philanthropist, and others, have donated the resources required to add these protocols to the Linux operating system. Linux is a complete, freely available operating system for IBM PC's and several kinds of workstation, which is compatible with Unix. It was written by Linus Torvalds, and is still maintained by a talented team of expert programmers working all over the world and coordinating over the Internet. Linux is distributed under the GNU Public License, which gives everyone the right to copy it, improve it, give it to their friends, sell it commercially, or do just about anything else with it, without paying anyone for the privilege.

Organizations that want to secure their network will be able to put two Ethernet cards into an IBM PC, install Linux on it from a $30 CDROM or by downloading it over the net, and plug it in between their Ethernet and their Internet link or firewall. That's all they'll have to do to encrypt their Internet traffic everywhere outside their own local area network.

Travelers will be able to run Linux on their laptops, to secure their connection back to their home network (and to everywhere else that they connect to, such as customer sites). Anyone who runs Linux on a standalone PC will also be able to secure their network connections, without changing their application software or how they operate their computer from day to day.

There are already numerous commercially available hardware and software products that use the IPSEC technology. The FreeS/WAN team regularly participates in interoperability tests to ensure that our software communicates cleanly and securely with other vendors' products.

Eventually IPSEC will move into the operating systems and networking protocol stacks of major vendors. This will probably take longer, because those vendors will have to figure out what they want to do about the export controls.

Current status

My initial goal of securing 5% of the net by Christmas '96 was not met. It was an ambitious goal, and inspired me and others to work hard, but was ultimately too ambitious. The protocols were in an early stage of development, and needed a lot more protocol design before they could be implemented. In April 1999, we released version 1.00 of the software, which is suitable for setting up Virtual Private Networks using shared secrets for authentication. It does not yet do opportunistic encryption, or use DNSSEC for authentication; those features are coming in a future release.

Check the FreeS/WAN web site for more frequently updated status.

The low-level encrypted packet formats are defined. The system for publishing keys and providing secure domain name service is defined. The IP Security working group has settled on a complex NSA-sponsored protocol for key agreement (called IKE). The protocol is not yet defined to enable opportunistic encryption or the use of DNSSEC keys.

Linux Implementation
The Linux implementation has reached its first major release and is ready for production use in manually-configured networks, using Linux kernel version 2.0.36. Later snapshots work on 2.2.x Linux kernels.

Domain Name System Security
All BIND releases starting with BIND-4.9.5 include support for the KEY records that will soon be needed by FreeS/WAN. The latest BIND releases, after 8.2, includes most DNS Security features, including cryptographic integrity protection if you sign your domain's records. BIND releases are available from the Internet Software Consortium FTP site. None of these BIND releases are export-controlled; the early ones don't contain cryptography, and the later ones merely use it for authentication, which is also exportable. Good documentation on the DNSSEC features is missing, though.


Because I can. I have made enough money from several successful startup companies, that for a while I don't have to work to support myself. I spend my energies and money creating the kind of world that I'd like to live in and that I'd like my (future) kids to live in. Keeping and improving on the civil rights we have in the United States, as we move more of our lives into cyberspace, is a particular goal of mine.

What You Can Do

Set up a Linux system
Get a machine running Linux (say the 6.1 release from Red Hat). Give the machine two Ethernet cards.
Install the Linux IPSEC (FreeS/WAN) software
If you're an experienced sysadmin or Linux hacker, install the freeswan-1.0 release, or any later release or snapshot. These releases do NOT provide automated "opportunistic" operation; they must be manually configured for each site you wish to encrypt with.
Get on the Linux FreeS/WAN mailing lists
Join the discussion forums for people working on the project, and testing the code and documentation.
Install a recent BIND at your site.
You won't be able to publish any keys for your domain, until you have upgraded your copy of BIND. The thing you really need from it is the new version of named, the Name Daemon, which knows about the KEY and SIG record types. So, download it from the Internet Software Consortium and install it on your name server machine (or get your system administrator, or Internet Service Provider, to install it). Both your primary DNS site and all of your secondary DNS sites will need the new release before you will be able to publish your keys. You can tell which sites this is by running the Unix command "dig MYDOMAIN ns" and seeing which sites are mentioned in your NS (name server) records.

Would you like to help? I can use people who are willing to write documentation, install early releases for testing, write cryptographic code outside the United States, support users and companies (for money) who want to use FreeS/WAN, sell pre-packaged software or systems including this technology, and teach classes for network administrators who want to install this technology. To offer to help, send me email at Tell me what country you live in and what your citizenship is (it matters due to the export control laws; personally I don't care). Include a copy of your resume and the URL of your home page. Describe what you'd like to do for the project, and what you're uniquely qualified for. Mention what other volunteer projects you've been involved in (and how they worked out). Helping out will require that you be able to commit to doing particular things, meet your commitments, and be responsive by email. Volunteer projects just don't work without those things.

Related projects

This prototype implementation of the IP Security protocols is for another free operating system. Download BSDipsec.tar.gz.
This prototype implementation of the IP Security protocols is for yet another free operating system. It is directly integrated into the OS release, since the OS is maintained in Canada, which has freedom of speech in software.

Misc notes

I've also collected a small bit of information about network encryption history and patents (warning: may be censored for Internet "Free Speech" violations).,, my home page (warning: may be censored for Internet "Free Speech" violations)

An equal opportunistic encryptor. Last updated $Date: 2003/05/13 23:05:18 $