Cryptography has a long and interesting history, and has been the subject of considerable political controversy.
The classic book on the history of cryptography is David Kahn's The Codebreakers. It traces codes and codebreaking from ancient Egypt to the 20th century.
Diffie and Landau Privacy on the Line: The Politics of Wiretapping and Encryption covers the history from the First World War to the 1990s, with an emphasis on the US.
During the Second World War, the British "Ultra" project achieved one of the greatest intelligence triumphs in the history of warfare, breaking many Axis codes. One major target was the Enigma cipher machine, a German device whose users were convinced it was unbreakable. The American "Magic" project had some similar triumphs against Japanese codes.
There are many books on this period. See our bibliography for several. Two I particularly like are:
Bletchley Park, where much of the Ultra work was done, now has a museum and a web site.
The Ultra work introduced three major innovations.
So by the end of the war, Allied code-breakers were expert at large-scale mechanised code-breaking. The payoffs were enormous.
The wartime innovations were enthusiastically adopted by post-war and Cold War signals intelligence agencies. Presumably many nations now have some agency capable of sophisticated attacks on communications security, and quite a few engage in such activity on a large scale.
America's NSA, for example, is said to be both the world's largest employer of mathematicians and the world's largest purchaser of computer equipment. Such claims may be somewhat exaggerated, but beyond doubt the NSA -- and similar agencies in other countries -- have some excellent mathematicians, lots of powerful computers, sophisticated software, and the organisation and funding to apply them on a large scale. Details of the NSA budget are secret, but there are some published estimates.
Changes in the world's communications systems since WW II have provided these agencies with new targets. Cracking the codes used on an enemy's military or diplomatic communications has been common practice for centuries. Extensive use of radio in war made large-scale attacks such as Ultra possible. Modern communications make it possible to go far beyond that. Consider listening in on cell phones, or intercepting electronic mail, or tapping into the huge volumes of data on new media such as fiber optics or satellite links. None of these targets existed in 1950. All of them can be attacked today, and almost certainly are being attacked.
The Ultra story was not made public until the 1970s. Much of the recent history of codes and code-breaking has not been made public, and some of it may never be. Two important books are:
Note that these books cover only part of what is actually going on, and then only the activities of nations open and democratic enough that (some of) what they are doing can be discovered. A full picture, including:
might be really frightening.
Until quite recently, cryptography was primarily a concern of governments, especially of the military, of spies, and of diplomats. Much of it was extremely secret.
In recent years, that has changed a great deal. With computers and networking becoming ubiquitous, cryptography is now important to almost everyone. Among the developments since the 1970s:
This has led to a complex ongoing battle between various mainly government groups wanting to control the spread of crypto and various others, notably the computer industry and the cypherpunk crypto advocates, wanting to encourage widespread use.
Steven Levy has written a fine history of much of this, called Crypto: How the Code rebels Beat the Government -- Saving Privacy in the Digital Age.
The FreeS/WAN project is to a large extent an outgrowth of cypherpunk ideas. Our reasons for doing the project can be seen in these quotes from the Cypherpunk Manifesto:
Privacy is necessary for an open society in the electronic age. ...
We cannot expect governments, corporations, or other large, faceless organizations to grant us privacy out of their beneficence. It is to their advantage to speak of us, and we should expect that they will speak. ...
We must defend our own privacy if we expect to have any. ...
Cypherpunks write code. We know that someone has to write software to defend privacy, and since we can't get privacy unless we all do, we're going to write it. We publish our code so that our fellow Cypherpunks may practice and play with it. Our code is free for all to use, worldwide. We don't much care if you don't approve of the software we write. We know that software can't be destroyed and that a widely dispersed system can't be shut down.
Cypherpunks deplore regulations on cryptography, for encryption is fundamentally a private act. ...
For privacy to be widespread it must be part of a social contract. People must come and together deploy these systems for the common good. ...
To quote project leader John Gilmore:
We are literally in a race between our ability to build and deploy technology, and their ability to build and deploy laws and treaties. Neither side is likely to back down or wise up until it has definitively lost the race.
If FreeS/WAN reaches its goal of making opportunistic encryption widespread so that secure communication can become the default for a large part of the net, we will have struck a major blow.
The political problem is that nearly all governments want to monitor their enemies' communications, and some want to monitor their citizens. They may be very interested in protecting some of their own communications, and often some types of business communication, but not in having everyone able to communicate securely. They therefore attempt to restrict availability of strong cryptography as much as possible.
Things various governments have tried or are trying include:
The government believes not only the governments associated with Echelon are able to intercept communication systems, but that it is an activity of the investigative authorities and intelligence services of many countries with governments of different political signature.Even if they have nothing on the scale of Echelon, most intelligence agencies and police forces certainly have some interception capability.
Of course governments are by no means the only threat to privacy and security on the net. Other threats include:
One study enumerates threats and possible responses for small and medium businesses. VPNs are a key part of the suggested strategy.
We consider privacy a human right. See the UN's Universal Declaration of Human Rights, article twelve:
No one shall be subjected to arbitrary interference with his privacy, family, home or correspondence, nor to attacks upon his honor and reputation. Everyone has the right to the protection of the law against such interference or attacks.
Our objective is to help make privacy possible on the Internet using cryptography strong enough not even those well-funded government agencies are likely to break it. If we can do that, the chances of anyone else breaking it are negliible.
Many groups are working in different ways to defend privacy on the net and elsewhere. Please consider contributing to one or more of these groups:
For more on these issues see:
There are several collections of crypto quotes on the net.
See also the bibliography and our list of web references on cryptography law and policy.
The remainder of this section includes two pieces of writing by our project leader
and discussions of:
and a section on press coverage of FreeS/WAN.
FreeS/WAN project founder John Gilmore wrote a web page about why we are doing this. The version below is slightly edited, to fit this format and to update some links. For a version without these edits, see his home page.
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 1997, 1998, and 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 FreeSwan to distinguish it from various commercial implementations. RSA came up with the term "S/WAN". Our main web site is at http://www.freeswan.org/. 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. 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 will also be numerous commercially available firewalls that use this technology. RSA Data Security is coordinating the S/Wan (Secure Wide Area Network) project among more than a dozen vendors who use these protocols. There's a compatability chart that shows which vendors have tested their boxes against which other vendors to guarantee interoperatility.
Eventually it will also 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.
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. As of April 1999, we have released version 1.0 of the software (freeswan-1.0.tar.gz), 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.
The first prototype implementation of Domain Name System Security was funded by DARPA as part of their Information Survivability program. Trusted Information Systems wrote a modified version of BIND, the widely-used Berkeley implementation of the Domain Name System.
TIS, ISC, and I merged the prototype into the standard version of BIND. The first production version that supports KEY and SIG records is bind-4.9.5. This or any later version of BIND will do for publishing keys. It is available from the Internet Software Consortium. This version of BIND is not export-controlled since it does not contain any cryptography. Later releases starting with BIND 8.2 include cryptography for authenticating DNS records, which is also exportable. Better documentation is needed.
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.
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, 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 email@example.com. 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.
From a message project leader John Gilmore posted to the mailing list:
John Denker wrote: > Indeed there are several ways in which the documentation overstates the > scope of what this project does -- starting with the name > FreeS/WAN. There's a big difference between having an encrypted IP tunnel > versus having a Secure Wide-Area Network. This software does a fine job of > the former, which is necessary but not sufficient for the latter. The goal of the project is to make it very hard to tap your wide area communications. The current system provides very good protection against passive attacks (wiretapping and those big antenna farms). Active attacks, which involve the intruder sending packets to your system (like packets that break into sendmail and give them a root shell :-) are much harder to guard against. Active attacks that involve sending people (breaking into your house and replacing parts of your computer with ones that transmit what you're doing) are also much harder to guard against. Though we are putting effort into protecting against active attacks, it's a much bigger job than merely providing strong encryption. It involves general computer security, and general physical security, which are two very expensive problems for even a site to solve, let alone to build into a whole society. The societal benefit of building an infrastructure that protects well against passive attacks is that it makes it much harder to do undetected bulk monitoring of the population. It's a defense against police-states, not against policemen. Policemen can put in the effort required to actively attack sites that they have strong suspicions about. But police states won't be able to build systems that automatically monitor everyone's communications. Either they will be able to monitor only a small subset of the populace (by targeting those who screwed up their passive security), or their monitoring activities will be detectable by those monitored (active attacks leave packet traces or footprints), which can then be addressed through the press and through political means if they become too widespread. FreeS/WAN does not protect very well against traffic analysis, which is a kind of widespread police-state style monitoring that still reveals significant information (who's talking to who) without revealing the contents of what was said. Defenses against traffic analysis are an open research problem. Zero Knowledge Systems is actively deploying a system designed to thwart it, designed by Ian Goldberg. The jury is out on whether it actually works; a lot more experience with it will be needed.
Notes on things mentioned in that message:
Various groups, especially governments and especially the US government, have a long history of advocating various forms of bogus security.
We regard bogus security as extremely dangerous. If users are deceived into relying on bogus security, then they may be exposed to large risks. They would be better off having no security and knowing it. At least then they would be careful about what they said.
Avoiding bogus security is a key design criterion for everything we do in FreeS/WAN. The most conspicuous example is our refusal to support single DES. Other IPsec "features" which we do not implement are discussed in our compatibility document.
Various governments have made persistent attempts to encourage or mandate "escrowed encrytion", also called "key recovery", or GAK for "government access to keys". The idea is that cryptographic keys be held by some third party and turned over to law enforcement or security agencies under some conditions.
Mary had a little key - she kept it in escrow, and every thing that Mary said, the feds were sure to know.
A crypto quotes page attributes this to Sam Simpson.
There is an excellent paper available on Risks of Escrowed Encryption, from a group of cryptographic luminaries which included our project leader.
Like any unnecessary complication, GAK tends to weaken security of any design it infects. For example:
FreeS/WAN does not support escrowed encryption, and never will.
Various governments, and some vendors, have also made persistent attempts to convince people that:
This is utter nonsense.
Weak systems touted include:
The notion that choice of ciphers or keysize should be determined by a trade-off between security requirements and overheads is pure bafflegab.
For example, suppose public key operations use use 1% of the time in a hybrid system and you triple the cost of public key operations. The cost of symmetric cipher operations is unchanged at 99% of the original total cost, so the overall effect is a jump from 99 + 1 = 100 to 99 + 3 = 102, a 2% rise in system cost.
In short, there has never been any technical reason to use inadequate ciphers. The only reason there has ever been for anyone to use such ciphers is that government agencies want weak ciphers used so that they can crack them. The alleged savings are simply propaganda.
Mary had a little key (It's all she could export), and all the email that she sent was opened at the Fort.
A crypto quotes page attributes this to Ron Rivest. NSA headquarters is at Fort Meade, Maryland.
Our policy in FreeS/WAN is to use only cryptographic components with adequate keylength and no known weaknesses.
Detailed discussion of which IPsec features we implement or omit is in out compatibility document.
These decisions imply that we cannot fully conform to the IPsec RFCs, since those have DES as the only required cipher and Group 1 as the only required DH group. (In our view, the standards were subverted into offerring bogus security.) Fortunately, we can still interoperate with most other IPsec implementations since nearly all implementers provide at least 3DES and Group 2 as well.
We hope that eventually the RFCs will catch up with our (and others') current practice and reject dubious components. Some of our team and a number of others are working on this in IETF working groups.
Of course, making systems secure does involve costs, and trade-offs can be made between cost and security. However, the real trade-offs have nothing to do with using weaker ciphers.
There can be substantial hardware and software costs. There are often substantial training costs, both to train administrators and to increase user awareness of security issues and procedures. There are almost always substantial staff or contracting costs.
Security takes staff time for planning, implementation, testing and auditing. Some of the issues are subtle; you need good (hence often expensive) people for this. You also need people to monitor your systems and respond to problems. The best safe ever built is insecure if an attacker can work on it for days without anyone noticing. Any computer is insecure if the administrator is "too busy" to check the logs.
Moreover, someone in your organisation (or on contract to it) needs to spend considerable time keeping up with new developments. EvilDoers will know about new attacks shortly after they are found. You need to know about them before your systems are attacked. If your vendor provides a patch, you need to apply it. If the vendor does nothing, you need to complain or start looking for another vendor.
For a fairly awful example, see this report. In that case over a million credit card numbers were taken from e-commerce sites, using security flaws in Windows NT servers. Microsoft had long since released patches for most or all of the flaws, but the site administrators had not applied them.
At an absolute minimum, you must do something about such issues before an exploitation tool is posted to the net for downloading by dozens of "script kiddies". Such a tool might appear at any time from the announcement of the security hole to several months later. Once it appears, anyone with a browser and an attitude can break any system whose administrators have done nothing about the flaw.
Compared to those costs, cipher overheads are an insignificant factor in the cost of security.
The only thing using a weak cipher can do for you is to cause all your other investment to be wasted.
Many nations restrict the export of cryptography and some restrict its use by their citizens or others within their borders.
US laws, as currently interpreted by the US government, forbid export of most cryptographic software from the US in machine-readable form without government permission. In general, the restrictions apply even if the software is widely-disseminated or public-domain and even if it came from outside the US originally. Cryptography is legally a munition and export is tightly controlled under the EAR Export Administration Regulations.
If you are a US citizen, your brain is considered US territory no matter where it is physically located at the moment. The US believes that its laws apply to its citizens everywhere, not just within the US. Providing technical assistance or advice to foreign "munitions" projects is illegal. The US government has very little sense of humor about this issue and does not consider good intentions to be sufficient excuse. Beware.
The official website for these regulations is run by the Commerce Department's Bureau of Export Administration (BXA).
The Bernstein case challenges the export restrictions on Constitutional grounds. Code is speech so restrictions on export of code violate the First Amendment's free speech provisions. This argument has succeeded in two levels of court so far. It is quite likely to go on to the Supreme Court.
The regulations were changed substantially in January 2000, apparently as a government attempt to get off the hook in the Bernstein case. It is now legal to export public domain source code for encryption, provided you notify the BXA.
There are, however, still restrictions in force. Moreover, the regulations can still be changed again whenever the government chooses to do so. Short of a Supreme Court ruling (in the Berstein case or another) that overturns the regulations completely, the problem of export regulation is not likely to go away in the forseeable future.
The FreeS/WAN project cannot accept software contributions, not even small bug fixes, from US citizens or residents. We want it to be absolutely clear that our distribution is not subject to US export law. Any contribution from an American might open that question to a debate we'd prefer to avoid. It might also put the contributor at serious legal risk.
Of course Americans can still make valuable contributions (many already have) by reporting bugs, or otherwise contributing to discussions, on the project mailing list. Since the list is public, this is clearly constitutionally protected free speech.
Note, however, that the export laws restrict Americans from providing technical assistance to foreign "munitions" projects. The government might claim that private discussions or correspondence with FreeS/WAN developers were covered by this. It is not clear what the courts would do with such a claim, so we strongly encourage Americans to use the list rather than risk the complications.
Some quotes from prominent cryptography experts:
The real aim of current policy is to ensure the continued effectiveness of US information warfare assets against individuals, businesses and governments in Europe and elsewhere.
Ross Anderson, Cambridge University
If the government were honest about its motives, then the debate about crypto export policy would have ended years ago.
Bruce Schneier, Counterpane Systems
The NSA regularly lies to people who ask it for advice on export control. They have no reason not to; accomplishing their goal by any legal means is fine by them. Lying by government employees is legal.
The Internet Architecture Board (IAB) and the Internet Engineering Steering Group (IESG) made a strong statement in favour of worldwide access to strong cryptography. Essentially the same statement is in the appropriately numbered RFC 1984. Two critical paragraphs are:
... various governments have actual or proposed policies on access to cryptographic technology ...
(a) ... export controls ...
(b) ... short cryptographic keys ...
(c) ... keys should be in the hands of the government or ...
(d) prohibit the use of cryptology ...
We believe that such policies are against the interests of consumers and the business community, are largely irrelevant to issues of military security, and provide only a marginal or illusory benefit to law enforcement agencies, ...
The IAB and IESG would like to encourage policies that allow ready access to uniform strong cryptographic technology for all Internet users in all countries.
Our goal in the FreeS/WAN project is to build just such "strong cryptographic technology" and to distribute it "for all Internet users in all countries".
More recently, the same two bodies (IESG and IAB) have issued RFC 2804 on why the IETF should not build wiretapping capabilities into protocols for the convenience of security or law enforcement agenicies. The abstract from that document is:
The Internet Engineering Task Force (IETF) has been asked to take a position on the inclusion into IETF standards-track documents of functionality designed to facilitate wiretapping.A quote from the debate leading up to that RFC:
This memo explains what the IETF thinks the question means, why its answer is "no", and what that answer means.
We should not be building surveillance technology into standards. Law enforcement was not supposed to be easy. Where it is easy, it's called a police state.
Jeff Schiller of MIT, in a discussion of FBI demands for wiretap capability on the net, as quoted by Wired.
The Raven mailing list was set up for this IETF discussion.
Our goal is to go beyond that RFC and prevent Internet wiretapping entirely.
Restrictions on the export of cryptography are not just US policy, though some consider the US at least partly to blame for the policies of other nations in this area.
A number of countries:
Argentina, Australia, Austria, Belgium, Bulgaria, Canada, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Japan, Luxembourg, Netherlands, New Zealand, Norway, Poland, Portugal, Republic of Korea, Romania, Russian Federation, Slovak Republic, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom and United States
have signed the Wassenaar Arrangement which restricts export of munitions and other tools of war. Cryptographic sofware is covered there.
Wassenaar details are available from the Wassenaar Secretariat, and elsewhere in a more readable HTML version.
For a critique see the GILC site:
The Global Internet Liberty Campaign (GILC) has begun a campaign calling for the removal of cryptography controls from the Wassenaar Arrangement.
The aim of the Wassenaar Arrangement is to prevent the build up of military capabilities that threaten regional and international security and stability . . .
There is no sound basis within the Wassenaar Arrangement for the continuation of any export controls on cryptographic products.
We agree entirely.
An interesting analysis of Wassenaar can be found on the cyber-rights.org site.
We believe our software is entirely exempt from these controls since the Wassenaar General Software Note says:
The Lists do not control "software" which is either:
- Generally available to the public by . . . retail . . . or
- "In the public domain".
There is a note restricting some of this, but it is a sub-heading under point 1, so it appears not to apply to public domain software.
Their glossary defines "In the public domain" as:
. . . "technology" or "software" which has been made available without restrictions upon its further dissemination.
N.B. Copyright restrictions do not remove "technology" or "software" from being "in the public domain".
We therefore believe that software freely distributed under the GNU Public License, such as Linux FreeS/WAN, is exempt from Wassenaar restrictions.
Most of the development work is being done in Canada. Our understanding is that the Canadian government accepts this interpretation.
Recent copies of the freely modifiable and distributable source code exist in many countries. Citizens all over the world participate in its use and evolution, and guard its ongoing distribution. Even if Canadian policy were to change, the software would continue to evolve in countries which do not restrict exports, and would continue to be imported from there into unfree countries. "The Net culture treats censorship as damage, and routes around it."
You can help. If you don't know of a Linux FreeS/WAN archive in your own country, please download it now to your personal machine, and consider making it publicly accessible if that doesn't violate your own laws. If you have the resources, consider going one step further and setting up a mirror site for the whole munitions Linux crypto software archive.
If you make Linux CD-ROMs, please consider including this code, in a way that violates no laws (in a free country, or in a domestic-only CD product).
Please send a note about any new archive mirror sites or CD distributions to firstname.lastname@example.org so we can update the documentation.
Lists of current mirror sites and of distributions which include FreeS/WAN are in our introduction section.
DES, the Data Encryption Standard, can no longer be considered secure. While no major flaws in its innards are known, it is fundamentally inadequate because its 56-bit key is too short. It is vulnerable to brute-force search of the whole key space, either by large collections of general-purpose machines or even more quickly by specialized hardware. Of course this also applies to any other cipher with only a 56-bit key. The only reason anyone could have for using a 56 or 64-bit key is to comply with various export laws intended to ensure the use of breakable ciphers.
Non-government cryptologists have been saying DES's 56-bit key was too short for some time -- some of them were saying it in the 70's when DES became a standard -- but the US government has consistently ridiculed such suggestions.
A group of well-known cryptographers looked at key lengths in a 1996 paper. They suggested a minimum of 75 bits to consider an existing cipher secure and a minimum of 90 bits for new ciphers. More recent papers, covering both symmetric and public key systems are at cryptosavvy.com and rsa.com. For all algorithms, the minimum keylengths recommended in such papers are significantly longer than the maximums allowed by various export laws.
In a 1998 ruling, a German court described DES as "out-of-date and not safe enough" and held a bank liable for using it.
The question of DES security has now been settled once and for all. In early 1998, the Electronic Frontier Foundation built a DES-cracking machine. It can find a DES key in an average of a few days' search. The details of all this, including complete code listings and complete plans for the machine, have been published in Cracking DES, by the Electronic Frontier Foundation.
That machine cost just over $200,000 to design and build. "Moore's Law" is that machines get faster (or cheaper, for the same speed) by roughly a factor of two every 18 months. At that rate, their $200,000 in 1998 becomes $50,000 in 2001.
However, Moore's Law is not exact and the $50,000 estimate does not allow for the fact that a copy based on the published EFF design would cost far less than the original. We cannot say exactly what such a cracker would cost today, but it would likely be somewhere between $10,000 and $100,000.
A large corporation could build one of these out of petty cash. The cost is low enough for a senior manager to hide it in a departmental budget and avoid having to announce or justify the project. Any government agency, from a major municipal police force up, could afford one. Or any other group with a respectable budget -- criminal organisations, political groups, labour unions, religious groups, ... Or any millionaire with an obsession or a grudge, or just strange taste in toys.
One might wonder if a private security or detective agency would have one for rent. They wouldn't need many clients to pay off that investment.
As for the security and intelligence agencies of various nations, they may have had DES crackers for years, and theirs may be much faster. It is difficult to make most computer applications work well on parallel machines, or to design specialised hardware to accelerate them. Cipher-cracking is one of the very few exceptions. It is entirely straightforward to speed up cracking by just adding hardware. Within very broad limits, you can make it as fast as you like if you have the budget. The EFF's $200,000 machine breaks DES in a few days. An aviation website gives the cost of a B1 bomber as $200,000,000. Spending that much, an intelligence agency could break DES in an average time of six and a half minutes.
That estimate assumes they use the EFF's 1998 technology and just spend more money. They may have an attack that is superior to brute force, they quite likely have better chip technology (Moore's law, a bigger budget, and whatever secret advances they may have made) and of course they may have spent the price of an aircraft carrier, not just one aircraft.
In short, we have no idea how quickly these organisations can break DES. Unless they're spectacularly incompetent or horribly underfunded, they can certainly break it, but we cannot guess how quickly. Pick any time unit between days and milliseconds; none is entirely unbelievable. More to the point, none of them is of any comfort if you don't want such organisations reading your communications.
Note that this may be a concern even if nothing you do is a threat to anyone's national security. An intelligence agency might well consider it to be in their national interest for certain companies to do well. If you're competing against such companies in a world market and that agency can read your secrets, you have a serious problem.
One might wonder about technology the former Soviet Union and its allies developed for cracking DES during the Cold War. They must have tried; the cipher was an American standard and widely used. Certainly those countries have some fine mathematicians, and those agencies had budget. How well did they succeed? Is their technology now for sale or rent?
Before the definitive EFF effort, DES had been cracked several times by people using many machines. See this press release for example.
A major corporation, university, or government department could break DES by using spare cycles on their existing collection of computers, by dedicating a group of otherwise surplus machines to the problem, or by combining the two approaches. It might take them weeks or months, rather than the days required for the EFF machine, but they could do it.
What about someone working alone, without the resources of a large organisation? For them, cracking DES will not be easy, but it may be possible. A few thousand dollars buys a lot of surplus workstations. A pile of such machines will certainly heat your garage nicely and might break DES in a few months or years. Or enroll at a university and use their machines. Or use an employer's machines. Or crack security somewhere and steal the resources to crack a DES key. Or write a virus that steals small amounts of resources on many machines. Or . . .
None of these approaches are easy or break DES really quickly, but an attacker only needs to find one that is feasible and breaks DES quickly enough to be dangerous. How much would you care to bet that this will be impossible if the attacker is clever and determined? How valuable is your data? Are you authorised to risk it on a dubious bet?
In short, it is now absolutely clear that DES is not secure against
That is why Linux FreeS/WAN disables all transforms which use plain DES for encryption.
DES is in the source code, because we need DES to implement our default encryption transform, Triple DES. We urge you not to use single DES. We do not provide any easy way to enable it in FreeS/WAN, and our policy is to provide no assistance to anyone wanting to do so.
The same is true, in spades, of ciphers -- DES or others -- crippled by 40-bit keys, as many ciphers were required to be until recently under various export laws. A brute force search of such a cipher's keyspace is 216 times faster than a similar search against DES. The EFF's machine can do a brute-force search of a 40-bit key space in seconds. One contest to crack a 40-bit cipher was won by a student using a few hundred idle machines at his university. It took only three and half hours.
We do not, and will not, implement any 40-bit cipher.
Triple DES, usually abbreviated 3DES, applies DES three times, with three different keys. DES seems to be basically an excellent cipher design; it has withstood several decades of intensive analysis without any disastrous flaws being found. It's only major flaw is that the small keyspace allows brute force attacks to succeeed. Triple DES enlarges the key space to 168 bits, making brute-force search a ridiculous impossibility.
3DES is currently the only block cipher implemented in FreeS/WAN. 3DES is, unfortunately, about 1/3 the speed of DES, but modern CPUs still do it at quite respectable speeds. Some speed measurements for our code are available.
The AES project has chosen a replacement for DES, a new standard cipher for use in non-classified US government work and in regulated industries such as banking. This cipher will almost certainly become widely used for many applications, including IPsec.
The winner, announced in October 2000 after several years of analysis and discussion, was the Rijndael cipher from two Belgian designers.
It is almost certain that FreeS/WAN will add AES support. AES patches are already available.
Strong Internet Privacy Software Free for Linux Users Worldwide Toronto, ON, April 14, 1999 - The Linux FreeS/WAN project today released free software to protect the privacy of Internet communications using strong encryption codes. FreeS/WAN automatically encrypts data as it crosses the Internet, to prevent unauthorized people from receiving or modifying it. One ordinary PC per site runs this free software under Linux to become a secure gateway in a Virtual Private Network, without having to modify users' operating systems or application software. The project built and released the software outside the United States, avoiding US government regulations which prohibit good privacy protection. FreeS/WAN version 1.0 is available immediately for downloading at http://www.xs4all.nl/~freeswan/. "Today's FreeS/WAN release allows network administrators to build excellent secure gateways out of old PCs at no cost, or using a cheap new PC," said John Gilmore, the entrepreneur who instigated the project in 1996. "They can build operational experience with strong network encryption and protect their users' most important communications worldwide." "The software was written outside the United States, and we do not accept contributions from US citizens or residents, so that it can be freely published for use in every country," said Henry Spencer, who built the release in Toronto, Canada. "Similar products based in the US require hard-to-get government export licenses before they can be provided to non-US users, and can never be simply published on a Web site. Our product is freely available worldwide for immediate downloading, at no cost." FreeS/WAN provides privacy against both quiet eavesdropping (such as "packet sniffing") and active attempts to compromise communications (such as impersonating participating computers). Secure "tunnels" carry information safely across the Internet between locations such as a company's main office, distant sales offices, and roaming laptops. This protects the privacy and integrity of all information sent among those locations, including sensitive intra-company email, financial transactions such as mergers and acquisitions, business negotiations, personal medical records, privileged correspondence with lawyers, and information about crimes or civil rights violations. The software will be particularly useful to frequent wiretapping targets such as private companies competing with government-owned companies, civil rights groups and lawyers, opposition political parties, and dissidents. FreeS/WAN provides privacy for Internet packets using the proposed standard Internet Protocol Security (IPSEC) protocols. FreeS/WAN negotiates strong keys using Diffie-Hellman key agreement with 1024-bit keys, and encrypts each packet with 168-bit Triple-DES (3DES). A modern $500 PC can set up a tunnel in less than a second, and can encrypt 6 megabits of packets per second, easily handling the whole available bandwidth at the vast majority of Internet sites. In preliminary testing, FreeS/WAN interoperated with 3DES IPSEC products from OpenBSD, PGP, SSH, Cisco, Raptor, and Xedia. Since FreeS/WAN is distributed as source code, its innards are open to review by outside experts and sophisticated users, reducing the chance of undetected bugs or hidden security compromises. The software has been in development for several years. It has been funded by several philanthropists interested in increased privacy on the Internet, including John Gilmore, co-founder of the Electronic Frontier Foundation, a leading online civil rights group. Press contacts: Hugh Daniel, +1 408 353 8124, email@example.com Henry Spencer, +1 416 690 6561, firstname.lastname@example.org * FreeS/WAN derives its name from S/WAN, which is a trademark of RSA Data Security, Inc; used by permission.