OpenSSH/Why Use Encryption

Encryption has been a hot topic in computing for a long time. It became a high priority item in national and international politics in 1991 when Dr. Phil Zimmermann at the Massachusetts Institute of Technology (MIT) first published Pretty Good Privacy (PGP). With the arrival of the first web shops, encryption went from a specialty to a requirement and increasing volumes of money changed hands online. By 1996, encryption became essential for e-business. By 2000, it became recognized as a general, essential prerequisite in electronic communication. Currently, in 2010, there is almost no chance of maintaining control over or integrity of any networked machine for more than a few minutes without the help of encryption.

Nowadays, much communication over computer networks is still done without encryption. That would be most communication, if inadequate encryption is also taken into account. This is despite years of warnings, government recommendations, best practice guidelines and incidents. As a result, any machine connected to the network can intercept communication that passes over that network. The eavesdroppers are many and varied. They include administrators, staff, employers, criminals, corporate spies, and even governments. Corporate espionage alone has become an enormous burden and barrier.

Businesses are well aware of dumpster diving and take precautions to shred all paper documents. But what about electronic information? Contracts and negotiations, trade secrets, patent applications, decisions and minutes, customer data and invoicing, personnel data, financial and tax records, calendars and schedules, product designs and production notes, training materials, and even regular correspondence go over the net daily. Archived materials, even if they are not accessed directly, are usually on machines that are available and accessed for other reasons.

Many company managers and executives are still unaware that their communications and documents are so easily intercepted, in spite of apparent and expensive access restrictions. In many cases these can be shown to be ineffectual and at best purely cosmetic. Security Theater is one obstacle and in the field of security it is more common to find snake oil than authentic solutions. Still, there is little public demonstration of awareness of the magnitude of corporate espionage nowadays or the cost of failure. Even failure to act has its costs. Not only is sensitive data available if left unencrypted, but also trends in less sensitive data can be spotted with a large enough sampling. A very large amount of information can be inferred even from lesser communications. Data mining is now a well-known concept as is the so-called wireless wiretap. With the increase in online material and activity, encryption is more relevant than ever even if many years have passed since the issues were first brought into the limelight.

Excerpt of ssh-1.0.0 README from July 12, 1995 edit

Tatu Ylönen, then at the Helsinki University of Technology, wrote the README[1] accompanying the early versions of his Open Source software, SSH. The following is an excerpt about why encryption is important.

ssh-1.0.0 README 1995-07-12



Currently, almost all communications in computer networks are done without encryption. As a consequence, anyone who has access to any machine connected to the network can listen in on any communication. This is being done by hackers, curious administrators, employers, criminals, industrial spies, and governments. Some networks leak off enough electromagnetic radiation that data may be captured even from a distance.

When you log in, your password goes in the network in plain text. Thus, any listener can then use your account to do any evil he likes. Many incidents have been encountered worldwide where crackers have started programs on workstations without the owners knowledge just to listen to the network and collect passwords. Programs for doing this are available on the Internet, or can be built by a competent programmer in a few days.

Any information that you type or is printed on your screen can be monitored, recorded, and analyzed. For example, an intruder who has penetrated a host connected to a major network can start a program that listens to all data flowing in the network, and whenever it encounters a 16-digit string, it checks if it is a valid credit card number (using the check digit), and saves the number plus any surrounding text (to catch expiration date and holder) in a file. When the intruder has collected a few thousand credit card numbers, he makes smallish mail-order purchases from a few thousand stores around the world, and disappears when the goods arrive but before anyone suspects anything.

Businesses have trade secrets, patent applications in preparation, pricing information, subcontractor information, client data, personnel data, financial information, etc. Currently, anyone with access to the network (any machine on the network) can listen to anything that goes in the network, without any regard to normal access restrictions.

Many companies are not aware that information can so easily be recovered from the network. They trust that their data is safe since nobody is supposed to know that there is sensitive information in the network, or because so much other data is transferred in the network. This is not a safe policy.

Individual persons also have confidential information, such as diaries, love letters, health care documents, information about their personal interests and habits, professional data, job applications, tax reports, political documents, unpublished manuscripts, etc.

There is also another frightening aspect about the poor security of communications. Computer storage and analysis capability has increased so much that it is feasible for governments, major companies, and criminal organizations to automatically analyze, identify, classify, and file information about millions of people over the years. Because most of the work can be automated, the cost of collecting this information is getting very low.

Government agencies may be able to monitor major communication systems, telephones, fax, computer networks, etc., and passively collect huge amounts of information about all people with any significant position in the society. Most of this information is not sensitive, and many people would say there is no harm in someone getting that information. However, the information starts to get sensitive when someone has enough of it. You may not mind someone knowing what you bought from the shop one random day, but you might not like someone knowing every small thing you have bought in the last ten years.

If the government some day starts to move into a more totalitarian direction, there is considerable danger of an ultimate totalitarian state. With enough information (the automatically collected records of an individual can be manually analyzed when the person becomes interesting), one can form a very detailed picture of the individual's interests, opinions, beliefs, habits, friends, lovers, weaknesses, etc. This information can be used to 1) locate any persons who might oppose the new system 2) use deception to disturb any organizations which might rise against the government 3) eliminate difficult individuals without anyone understanding what happened. Additionally, if the government can monitor communications too effectively, it becomes too easy to locate and eliminate any persons distributing information contrary to the official truth.

Fighting crime and terrorism are often used as grounds for domestic surveillance and restricting encryption. These are good goals, but there is considerable danger that the surveillance data starts to get used for questionable purposes. I find that it is better to tolerate a small amount of crime in the society than to let the society become fully controlled. I am in favor of a fairly strong state, but the state must never get so strong that people become unable to spread contra-official information and unable to overturn the government if it is bad. The danger is that when you notice that the government is too powerful, it is too late. Also, the real power may not be where the official government is.

For these reasons (privacy, protecting trade secrets, and making it more difficult to create a totalitarian state), I think that strong cryptography should be integrated to the tools we use every day. Using it causes no harm (except for those who wish to monitor everything), but not using it can cause huge problems. If the society changes in undesirable ways, then it will be to late to start encrypting.

Encryption has had a "military" or "classified" flavor to it. There are no longer any grounds for this. The military can and will use its own encryption; that is no excuse to prevent the civilians from protecting their privacy and secrets. Information on strong encryption is available in every major bookstore, scientific library, and patent office around the world, and strong encryption software is available in every country on the Internet.

Some people would like to make it illegal to use encryption, or to force people to use encryption that governments can break. This approach offers no protection if the government turns bad. Also, the "bad guys" will be using true strong encryption anyway. Thus, any "key escrow encryption" or whatever it might be called only serves to help monitor the ordinary people and petty criminals; it does not help against powerful criminals, terrorists, or espionage, because they will know how to use strong encryption anyway.


Thanks also go to Philip Zimmermann, whose PGP software and the associated legal battle provided inspiration, motivation, and many useful techniques, and to Bruce Schneier whose book Applied Cryptography has done a great service in widely distributing knowledge about cryptographic methods.


ssh-1.0.0 README 1995-07-12

Phil Zimmermann on encryption and privacy, from 1991, updated 1999 edit

Phil Zimmermann wrote the encryption tool Pretty Good Privacy (PGP) in 1991 to promote privacy and to help keep encryption, and thus privacy, legal around the world. Considerable difficulty occurred in the United States until PGP was published outside and re-imported in a very visible, public manner.

Why I Wrote PGP
Part of the Original 1991 PGP User's Guide (updated in 1999)

"Whatever you do will be insignificant, but it is very important that you do it."

–Mahatma Gandhi.

It's personal. It's private. And it's no one's business but yours. You may be planning a political campaign, discussing your taxes, or having a secret romance. Or you may be communicating with a political dissident in a repressive country. Whatever it is, you don't want your private electronic mail (email) or confidential documents read by anyone else. There's nothing wrong with asserting your privacy. Privacy is as apple-pie as the Constitution.

The right to privacy is spread implicitly throughout the Bill of Rights. But when the United States Constitution was framed, the Founding Fathers saw no need to explicitly spell out the right to a private conversation. That would have been silly. Two hundred years ago, all conversations were private. If someone else was within earshot, you could just go out behind the barn and have your conversation there. No one could listen in without your knowledge. The right to a private conversation was a natural right, not just in a philosophical sense, but in a law-of-physics sense, given the technology of the time.

But with the coming of the information age, starting with the invention of the telephone, all that has changed. Now most of our conversations are conducted electronically. This allows our most intimate conversations to be exposed without our knowledge. Cellular phone calls may be monitored by anyone with a radio. Electronic mail, sent across the Internet, is no more secure than cellular phone calls. Email is rapidly replacing postal mail, becoming the norm for everyone, not the novelty it was in the past.

Until recently, if the government wanted to violate the privacy of ordinary citizens, they had to expend a certain amount of expense and labor to intercept and steam open and read paper mail. Or they had to listen to and possibly transcribe spoken telephone conversation, at least before automatic voice recognition technology became available. This kind of labor-intensive monitoring was not practical on a large scale. It was only done in important cases when it seemed worthwhile. This is like catching one fish at a time, with a hook and line. Today, email can be routinely and automatically scanned for interesting keywords, on a vast scale, without detection. This is like driftnet fishing. And exponential growth in computer power is making the same thing possible with voice traffic.

Perhaps you think your email is legitimate enough that encryption is unwarranted. If you really are a law-abiding citizen with nothing to hide, then why don't you always send your paper mail on postcards? Why not submit to drug testing on demand? Why require a warrant for police searches of your house? Are you trying to hide something? If you hide your mail inside envelopes, does that mean you must be a subversive or a drug dealer, or maybe a paranoid nut? Do law-abiding citizens have any need to encrypt their email?

What if everyone believed that law-abiding citizens should use postcards for their mail? If a nonconformist tried to assert his privacy by using an envelope for his mail, it would draw suspicion. Perhaps the authorities would open his mail to see what he's hiding. Fortunately, we don't live in that kind of world, because everyone protects most of their mail with envelopes. So no one draws suspicion by asserting their privacy with an envelope. There's safety in numbers. Analogously, it would be nice if everyone routinely used encryption for all their email, innocent or not, so that no one drew suspicion by asserting their email privacy with encryption. Think of it as a form of solidarity.

Senate Bill 266, a 1991 omnibus anticrime bill, had an unsettling measure buried in it. If this non-binding resolution had become real law, it would have forced manufacturers of secure communications equipment to insert special "trap doors" in their products, so that the government could read anyone's encrypted messages. It reads, "It is the sense of Congress that providers of electronic communications services and manufacturers of electronic communications service equipment shall ensure that communications systems permit the government to obtain the plain text contents of voice, data, and other communications when appropriately authorized by law." It was this bill that led me to publish PGP electronically for free that year, shortly before the measure was defeated after vigorous protest by civil libertarians and industry groups.

The 1994 Communications Assistance for Law Enforcement Act (CALEA) mandated that phone companies install remote wiretapping ports into their central office digital switches, creating a new technology infrastructure for "point-and-click" wiretapping, so that federal agents no longer have to go out and attach alligator clips to phone lines. Now they will be able to sit in their headquarters in Washington and listen in on your phone calls. Of course, the law still requires a court order for a wiretap. But while technology infrastructures can persist for generations, laws and policies can change overnight. Once a communications infrastructure optimized for surveillance becomes entrenched, a shift in political conditions may lead to abuse of this new-found power. Political conditions may shift with the election of a new government, or perhaps more abruptly from the bombing of a federal building.

A year after the CALEA passed, the FBI disclosed plans to require the phone companies to build into their infrastructure the capacity to simultaneously wiretap 1 percent of all phone calls in all major U.S. cities. This would represent more than a thousandfold increase over previous levels in the number of phones that could be wiretapped. In previous years, there were only about a thousand court-ordered wiretaps in the United States per year, at the federal, state, and local levels combined. It's hard to see how the government could even employ enough judges to sign enough wiretap orders to wiretap 1 percent of all our phone calls, much less hire enough federal agents to sit and listen to all that traffic in real time. The only plausible way of processing that amount of traffic is a massive Orwellian application of automated voice recognition technology to sift through it all, searching for interesting keywords or searching for a particular speaker's voice. If the government doesn't find the target in the first 1 percent sample, the wiretaps can be shifted over to a different 1 percent until the target is found, or until everyone's phone line has been checked for subversive traffic. The FBI said they need this capacity to plan for the future. This plan sparked such outrage that it was defeated in Congress. But the mere fact that the FBI even asked for these broad powers is revealing of their agenda.

Advances in technology will not permit the maintenance of the status quo, as far as privacy is concerned. The status quo is unstable. If we do nothing, new technologies will give the government new automatic surveillance capabilities that Stalin could never have dreamed of. The only way to hold the line on privacy in the information age is strong cryptography.

You don't have to distrust the government to want to use cryptography. Your business can be wiretapped by business rivals, organized crime, or foreign governments. Several foreign governments, for example, admit to using their signals intelligence against companies from other countries to give their own corporations a competitive edge. Ironically, the United States government's restrictions on cryptography in the 1990's have weakened U.S. corporate defenses against foreign intelligence and organized crime.

The government knows what a pivotal role cryptography is destined to play in the power relationship with its people. In April 1993, the Clinton administration unveiled a bold new encryption policy initiative, which had been under development at the National Security Agency (NSA) since the start of the Bush administration. The centerpiece of this initiative was a government-built encryption device, called the Clipper chip, containing a new classified NSA encryption algorithm. The government tried to encourage private industry to design it into all their secure communication products, such as secure phones, secure faxes, and so on. AT&T put Clipper into its secure voice products. The catch: At the time of manufacture, each Clipper chip is loaded with its own unique key, and the government gets to keep a copy, placed in escrow. Not to worry, though–the government promises that they will use these keys to read your traffic only "when duly authorized by law." Of course, to make Clipper completely effective, the next logical step would be to outlaw other forms of cryptography.

The government initially claimed that using Clipper would be voluntary, that no one would be forced to use it instead of other types of cryptography. But the public reaction against the Clipper chip was strong, stronger than the government anticipated. The computer industry monolithically proclaimed its opposition to using Clipper. FBI director Louis Freeh responded to a question in a press conference in 1994 by saying that if Clipper failed to gain public support, and FBI wiretaps were shut out by non-government-controlled cryptography, his office would have no choice but to seek legislative relief. Later, in the aftermath of the Oklahoma City tragedy, Mr. Freeh testified before the Senate Judiciary Committee that public availability of strong cryptography must be curtailed by the government (although no one had suggested that cryptography was used by the bombers).

The government has a track record that does not inspire confidence that they will never abuse our civil liberties. The FBI's COINTELPRO program targeted groups that opposed government policies. They spied on the antiwar movement and the civil rights movement. They wiretapped the phone of Martin Luther King. Nixon had his enemies list. Then there was the Watergate mess. More recently, Congress has either attempted to or succeeded in passing laws curtailing our civil liberties on the Internet. Some elements of the Clinton White House collected confidential FBI files on Republican civil servants, conceivably for political exploitation. And some overzealous prosecutors have shown a willingness to go to the ends of the Earth in pursuit of exposing sexual indiscretions of political enemies. At no time in the past century has public distrust of the government been so broadly distributed across the political spectrum, as it is today.

Throughout the 1990s, I figured that if we want to resist this unsettling trend in the government to outlaw cryptography, one measure we can apply is to use cryptography as much as we can now while it's still legal. When use of strong cryptography becomes popular, it's harder for the government to criminalize it. Therefore, using PGP is good for preserving democracy. If privacy is outlawed, only outlaws will have privacy.

It appears that the deployment of PGP must have worked, along with years of steady public outcry and industry pressure to relax the export controls. In the closing months of 1999, the Clinton administration announced a radical shift in export policy for crypto technology. They essentially threw out the whole export control regime. Now, we are finally able to export strong cryptography, with no upper limits on strength. It has been a long struggle, but we have finally won, at least on the export control front in the US. Now we must continue our efforts to deploy strong crypto, to blunt the effects increasing surveillance efforts on the Internet by various governments. And we still need to entrench our right to use it domestically over the objections of the FBI.

PGP empowers people to take their privacy into their own hands. There has been a growing social need for it. That's why I wrote it.

Philip R. Zimmermann
Boulder, Colorado
June 1991 (updated 1999)[2]

Original Press Release for OpenSSH edit

Below is the original press release for OpenSSH sent back in 1999.[3]

Date: Mon, 25 Oct 1999 00:04:29 -0600 (MDT)
From: Louis Bertrand <louis>
To: Liz Coolbaugh <lwn>
Subject: OpenBSD Press Release: OpenSSH integrated into operating system


OpenSSH: Secure Shell integrated into OpenBSD operating system

Source: OpenBSD

Louis Bertrand, OpenBSD media relations
Bertrand Technical Services
Tel: (905) 623-8925 Fax: (905) 623-3852
Theo de Raadt, OpenBSD lead developer

Project Web site:

OpenSSH: Secure Shell integrated into OpenBSD Secure communications package no longer third-party add-on

[October 25, 1999: Calgary, Canada] -- The OpenBSD developers are pleased to announce the release of OpenSSH, a free implementation of the popular Secure Shell encrypted communications package. OpenSSH, to be released with OpenBSD 2.6, is compatible with both SSH 1.3 and 1.5 protocols and dodges most restrictions on the free distribution of strong cryptography.

OpenSSH is based on a free release of SSH by Tatu Ylonen, with major changes to remove proprietary code and bring it up to current security and functionality standards. Secure Shell operates like the popular TELNET remote terminal package but with an encrypted link between the user and the remote server. SSH also allows "tunnelling" of network services through the scrambled connection for added privacy. OpenSSH has been tested to interoperate with ssh-1.2.27 from SSH Communications, and the TTSSH and SecureCRT Windows clients.

"Network sessions involving strong cryptographic security are a requirement in the modern world," says lead developer Theo de Raadt. "Everyone needs this. People using the telnet or rlogin protocols are not aware of the extreme danger posed by password sniffing and session hijacking."

In previous releases of OpenBSD, users were urged to download SSH as soon as possible after installing the OS. Without SSH, terminal sessions transmitted in clear text allow eavesdroppers on the Internet to capture user names and password combinations and thus bypass the security measures in the operating system.

"I asked everyone `what is the first thing you do after installing OpenBSD?' Everyone gave me the same answer: they installed ssh," says de Raadt. "That's a pain, so we've made it much easier."

All proprietary code in the original distribution was replaced, along with some libraries burdened with the restrictive GNU Public License (GPL). Much of of the actual cryptographic code was replaced by calls to the crypto libraries built into OpenBSD. The source code is now completely freely re-useable, and vendors are encouraged to re-use it if they need ssh functionality.

OpenSSH relies on the Secure Sockets Layer library (libssl) which incorporates the RSA public-key cryptography system. RSA is patented in the US and OpenBSD developers must work around the patent restrictions. Users outside the US may download a libssl file based on the patent-free OpenSSL implementation. For US non-commercial users, OpenBSD is preparing a libssl based on the patented RSAREF code. Unfortunately, the US legal framework effectively bans US commercial users from using OpenSSH, and curtails freedom of choice in that market.

OpenSSH was developed and integrated into OpenBSD by Niels Provos, Theo de Raadt, Markus Friedl for cryptographic work; Dug Song, Aaron Campbell, and others for various non-crypto contributions; and Bob Beck for helping with the openssl library issues. The original SSH was written by Tatu Ylonen. Bjoern Groenvall and Holger Trapp did the initial work to free the distribution.

OpenBSD is an Internet-based volunteer effort to produce a secure multi-platform operating system with built-in support for cryptography. It has been described in the press as the world's most secure operating system. For more information about OpenSSH and OpenBSD, see the project Web pages at

Source: OpenBSD

The European Union (EU) on Encryption edit

During 2000, the European Commission investigated the state of international and industrial electronic espionage. Counter-measures and solutions were investigated as well as the risks. The result was a resolution containing a summary of the findings and a series of recommended actions for Member States to carry out and goals to meet. Recommendations to EU Member States from the European Parliament resolution ECHELON, A5-0264/2001 (emphasis added):

"29. Urges the Commission and Member States to devise appropriate measures to promote, develop and manufacture European encryption technology and software and above all to support projects at developing user-friendly open-source encryption software;"
. . .
"33. Calls on the Community institutions and the public administrations of the Member States to provide training for their staff and make their staff familiar with new encryption technologies and techniques by means of the necessary practical training and courses;"[4]

It was found during the investigation that businesses were the most at risk and the most vulnerable and that widespread use of open source encryption technology is to be encouraged. The same can be said even today.

References edit

  1. "SSH 1.0.0 README". FUNET. 1995.
  2. Phil Zimmermann (1991). "Why I Wrote PGP". Massachusetts Institute of Technology. Retrieved 2011-02-18.
  3. "OpenSSH: Secure Shell integrated into OpenBSD operating system". LWN. 1999. Retrieved 2011-02-18.
  4. "European Parliament resolution on the existence of a global system for the interception of private and commercial communications (ECHELON interception system) (2001/2098(INI))". European Parliament. 2001. ECHELON A5-0264 2001. Retrieved 2011-02-18.