FreeSWAN

FreeS/WAN [1] was the original Linux implementation of the IPsec protocols. The name was based, with permission, on the RSA Laboratories trademark "S/WAN" which stands for for "secure wide area network".

It was was very much a politically-motivated cypherpunk project. The overall goal was to stop widespread Internet monitoring by organisations such as the NSA, the Chinese government, and others. This was to be accomplished by deploying IPsec-based opportunistic encryption very widely.

Opportunistic encryption allows any two machines to communicate securely, without any connection-specific setup by the administrators. The administrator sets up the machines, sets policies, and puts authentication keys in DNS. Once that is done, the machines themselves build and manage the connections without further administrator input. For large networks, the saving in administrator time is enormous; with $n$ machines and an approach that requires administrator to configure each connection, the work increases as $n$ squared. For opportunistic encryption, it increases linearly with $n$.

Even more important, for FreeS/WAN purposes, opportunistic encryption allows any two machines to communicate securely, even if their administrators have had no contact with each other. With opportunistic encryption, secure communication could be the default and a significant fraction of all Internet traffic encrypted. This may not stop a policeman who has a specific suspicion and is willing to expend effort against a specific target to get evidence. It does stop wholesale monitoring, the "Big Brother is listening" approach of a police state. Widespread opportunistic encryption would put the monitoring agencies' big antenna farms out of business, or leave them with only traffic analysis to go on. That was FreeSWAN's goal.

The authentication keys needed for secure connection setup are in DNS; any two machines can get each other's keys from DNS and create a secure connection. This alone is secure against passive eavesdroppers; protect the authentication data with DNS security and it is also secure against active attackers. See RFC 4322 "Opportunistic Encryption using the Internet Key Exchange (IKE)", written by members of the FreeSWAN team, for details.

Project leader was activist and Electronic Frontier Foundation [2] co-founder John Gilmore [3]. Technical lead was Canadian Unix guru Henry Spencer [4].

The project refused to implement weak cryptography, even where the RFCs required it. Their position was that the RFCs had unfortunately been subverted into including weak methods, but there was still no excuse for actually implementing those. Among the things rejected were null encryption, single DES, and Oakley Group 1. This did not generally lead to interoperation problems, even though those were the only required algorithms in the RFCs. Almost everyone implemented the more secure Triple DES and groups two and five, so almost everyone could talk to FreeS/WAN. Some users wanted single DES; the project explicitly refused to provide any assistance for that.

The project also refused to expend effort on adding features that did not lead toward the main goal, wide deployment of Opportunistic encryption. Building a general-purpose IPsec implementation for Linux was always seen as a byproduct of work toward that main goal — perhaps an interesting and important byproduct, but still a byproduct. Adding things like IPv6 support or authentication using X.509 certificates was seen as a distraction from the main work. Users did add these and some of their work was incorporated into the main FreeS/WAN distribution.

All work was done in Canada by Canadians to avoid US export laws. To ensure that it remained free of those laws, the project would not accept even a one-line bug fix from an American resident or citizen.

Later the Linux kernel team included a different IPsec implementation — one that Americans could contribute to and that was more amenable to adding features — in the kernel, and added KAME-based tools at the user level. Most current Linux distributions include those.

The "Moat" paper documents a large FreeS/WAN deployment at AT&T Laboratories.

The FreeS/WAN project shut down in 2002, without having achieved the goal of making Opportunistic encryption widespread.

Two descendants exist, StrongSWAN and OpenSWAN.

FreeS/WAN's main technical writer is now a Citizendium author, and has permission to reuse FreeS/WAN material here.