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What the Cypherpunks Got Wrong

Cypherpunk ideas have a long legacy and continue to influence how we are discussion matters of security and privacy, particularly in the relationship between citizens and governments. In a nutshell, cypherpunks posit that we can and should keep government intervention minimal by force-protecting our privacy by means of encryption.

Let us begin with what they got right:

“For privacy to be widespread it must be part of a social contract.”

 (Eric Hughes: A Cypherpunk’s Manifesto)

Social contracts are the basis of every society; they define a society and are represented in its formal and informal norms. Privacy is indeed a matter of social contract as it concerns very fundamental question of what the members of a society should know about each other, how they should they should learn it, and how they may or may not use what they know about others.

Privacy is not merely a matter of hiding information so that it cannot be found. The absence of expected features or utterances carries information, too. Some societies, for example, expect their members to actively demonstrate their allegiance. Members of such a society cannot merely hide what they think, they also have to perform their role as expected if they have no desire to become a leper.

What the cypherpunks got entirely wrong was their conception of social contracts and the hope that cryptography could be the foundation upon which they, the cypherpunks, would build their own. Cypherpunks believe that cryptography would allow them to define their own social contract on top of or next to the existing ones. This has not worked and it cannot work. On the one hand, this is not how social contracts work. They are a dimension of a society’s culture that evolves, for better or worse, with this society.

On the other hand, cryptography–or security technology in general–does not change power relationships as much as cypherpunks hope it would. Governments are by definition institutions of power: “Government is the means by which state policy is enforced.” Cypherpunks believe that cryptography and other means of keeping data private would limit the power of their governments and lay it into the cypherpunks’ hands. However, the most fundamental power that any working government has is the power to detain members of the society it is governing.

In an echo of cypherpunk thinking, some people react to an increased interest of the U.S. Customs and Border Protection (CBP) in travelers’ mobile devices with the suggestion to leave those devices at home while traveling. After all, the CBP cannot force you to surrender what you do not have on you, so the reasoning. This thinking has, however, several flaws.

First, from a security point of view, leaving your phone at home means to leave it just as unattended as it would be in the hands of a CBP agent. If the government really wants your data, nothing better could happen to them than getting access to your phone while you are not even in the country.

Second, the government is interested in phones for a reason. Cryptography and other security mechanisms do not solve security problems, they only transform them. Cryptography in particular transforms the problem of securing data into a problem of securing keys. The use of technology has evolved in many societies to the point where our phones have become our keys to almost everything we do and own online; they have become our primary window into the cloud. This makes phones and the data on them valuable in every respect, for those trying to exert power as well as for ourselves. You lose this value if you refrain from using your phone. Although it seems easy to just leave your phone at home, the hidden cost of it is hefty. Advice suggesting that you do so is therefore not very practical.

Third, this is not about you (or if it is, see #1 above). Everyone is using mobile phones and cloud services because of their tremendous value. Any government interested in private information will adapt its approach to collecting this information to the ways people usually behave. You can indeed gain an advantage sometimes by just being different, by not behaving as everyone else would. This can work for you, particularly if the government’s interest in your affairs is only a general one and they spend only average effort on you. However, this same strategy will not work for everyone as everyone cannot be different. If everyone left their phones at home, your government would find a different way of collecting information.

By ignoring a bit of context, cypherpunks manage to arrive at wrong conclusions from right axioms:

“We cannot expect governments, corporations, or other large, faceless organizations to grant us privacy out of their beneficence.”

“We must defend our own privacy if we expect to have any.”

(Eric Hughes: A Cypherpunk’s Manifesto)

This is true, but incomplete. Power must be contained at its source (and containment failures are a real possibility). Cryptography and other security technology does not do that. Cryptography can perhaps help you evade power under certain circumstances, but it will by no means reverse power relationships. What you really need is a social contract that guarantees your freedom ad dignity.

 

(Expanded version of a G+ comment)

 

Encryption Will Not Give You Free Speech

“Freedom of speech is the right to articulate one’s opinions and ideas without fear of government retaliation or censorship, or societal sanction.”Wikipedia

Reports of a vulnerability in WhatsApp are making the rounds today after The Guardian boosted the signal. Besides the fact that there is not really a backdoor, but rather a feature that represents a reasonable choice in a tradeoff between confidentiality and availability, the Guardian also repeats a common mistake: confounding encryption and free speech.

“Privacy campaigners criticise WhatsApp vulnerability as a ‘huge threat to freedom of speech,’” writes The Guardian. This is bullshit. As per the definition cited above, free speech means you can say things without fear. Being able to say things only in private and needing strong technical privacy guarantees is the opposite of free speech. You need encryption for that which you cannot say without fear.

Yes, encryption can be a tool against those who suppress you (though a weak one, as your adversary can easily use your use of encryption against you – or deny you due process altogether and persecute you without any trace of evidence and probable cause). But encryption will never give you free speech, it will only support your inner immigration.

An In-Depth Study of More Than Ten Years of Java Exploitation

My colleagues Philipp Holzinger, Stefan Triller, Alexandre Bartel, and Eric Bodden had a closer look at Java and the vulnerabilities discovered in the Java runtime environment during the last decade. They started from known exploits, identified the vulnerabilities exploited, and analyzed and grouped their root causes. Philipp’s presentation of the results at CCS’16 has been recorded and published on YouTube:

(YouTube)

The paper is also available online:

P. Holzinger, S. Triller, A. Bartel, E. Bodden: An In-Depth Study of More Than Ten Years of Java Exploitation. Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security (CCS’16), Vienna, Austria, Oct. 24-28, 2016. DOI: 10.1145/2976749.2978361. Artifacts: ccs2016-artifacts-v01.zip

 

Classifying Vehicles

Security is a classification problem: Security mechanisms, or combinations of mechanisms, need to distinguish that which they should allow to happen from that which they should deny. Two aspects complicate this task. First, security mechanisms often only solve a proxy problem. Authentication mechanisms, for example, usually distinguish some form of token – passwords, keys, sensor input, etc. – rather than the actual actors. Second, adversaries attempt to shape their appearance to pass security mechanisms. To be effective, a security mechanism needs to cover these adaptations, at least the feasible ones.

An everyday problem illustrates this: closing roads for some vehicles but not for others. As a universal but costly solution one might install retractable bollards, issue means to operate them to the drivers of permitted vehicles, and prosecute abuse. This approach is very precise, because classification rests on an artificial feature designed solely for security purposes.

Simpler mechanisms can work sufficiently well if (a) intrinsic features of vehicles are correlated with the desired classification well enough, and (b) modification of these features is subject to constraints so that evading the classifier is infeasible within the adversary model.

Bus traps and sump busters classify vehicles by size, letting lorries and buses pass while stopping common passenger cars. The real intention is to classify vehicles by purpose and operator, but physical dimensions happen to constitute a sufficiently good approximation. Vehicle size correlates with purpose. The distribution of sizes is skewed; there are many more passenger cars than buses, so keeping even just most of them out does a lot. Vehicle dimensions do not change on the fly, and are interdependent with other features and requirements. Although a straightforward way exists to defeat a bus trap – get a car that can pass – this is too expensive for most potential adversaries and their possible gain from the attack.

Unexpected Moves

When AlphaGo played and won against Sedol, it made innovative moves not only unexpected by human experts but also not easily understandable for humans. Apparently this shocked and scared some folks.

However, AI coming up with different concepts than humans is nothing new. Consider this article recounting the story of Eurisko, a genetic programming experiment in the late 1970s. This experiment, too, aimed at competing in a tournament; the game played, Traveller TCS, was apparently about designing fleets of ships and letting them fight against each other. Even this early, simple, and small-scale AI thing surprised human observers:

“To the humans in the tournament, the program’s solution to Traveller must have seemed bizarre. Most of the contestants squandered their trillion-credit budgets on fancy weaponry, designing agile fleets of about twenty lightly armored ships, each armed with one enormous gun and numerous beam weapons.”

(G. Johnson:
Eurisko, The Computer With A Mind Of Its Own)

Keep in mind there was nothing scary in the algorithm, it was really just simulated evolution in a rather small design space and the computer needed some help by its programmers to succeed.

The Eurisko “AI” even rediscovered the concept of outnumbering the enemy instead of overpowering him, a concept humans might associate with Lanchester’s models of predator-prey systems:

“Eurisko, however, had judged that defense was more important than offense, that many cheap, invulnerable ships would outlast fleets consisting of a few high-priced, sophisticated vessels. (…) In any single exchange of gunfire, Eurisko would lose more ships than it destroyed, but it had plenty to spare.”

(G. Johnson:
Eurisko, The Computer With A Mind Of Its Own)

Although Eurisko’s approach seemed “un-human”, it really was not. Eurisko only ignored all human biases and intuition, making decisions strictly by cold, hard data. This is a common theme in data mining, machine learning, and AI applications. Recommender systems, for example, create and use concepts unlike those a human would apply to the same situation; an article in IEEE Spectrum a couple of years ago (J. A. Konstan, J. Riedl: Deconstructing Recommender Systems) outlined a food recommender example and pointed out that concepts like “salty” would not appear in their models.

Transparency and auditability are surely problems if such technology is being used in critical applications. Whether we should be scared beyond this particular problem remains an open question.

 

(This is a slightly revised version of my G+ post, https://plus.google.com/+SvenT%C3%BCrpe/posts/5QE9KeFKKch)

The Key-Under-the-Doormat Analogy Has a Flaw

The crypto wars are back, and with them the analogy of putting keys under the doormat:

… you can’t build a backdoor into our digital devices that only good guys can use. Just like you can’t put a key under a doormat that only the FBI will ever find.

(Rainey Reitman: An Open Letter to President Obama: This is About Math, Not Politics)

This is only truthy. The problem of distinguishing desirable from undesirable interactions to permit the former and deny the latter lies indeed at the heart of any security problem. I have been arguing for years that security is a classification problem; any key management challenge reminds us of it. I have no doubt that designing a crypto backdoor only law enforcement can use only for legitimate purposes, or any sufficiently close approximation, is a problem we remain far from solving for the foreseeable future.

However, the key-under-the-doormat analogy misrepresents the consequences of not putting keys under the doormat, or at least does not properly explain them. Other than (idealized) crypto, our houses and apartments are not particularly secure to begin with. Even without finding a key under the doormat, SWAT teams and burglars alike can enter with moderate effort. This allows legitimate law enforecement to take place at the cost of a burglary (etc.) risk.

Cryptography can be different. Although real-world implementations often have just as many weaknesses as the physical security of our homes, cryptography can create situations where only a backdoor would allow access to plaintext. If all we have is a properly encrypted blob, there is little hope of finding out anything about its plaintext. This does not imply we must have provisions to avoid that situation no matter what the downsides are, but it does contain a valid problem statement: How should we regulate technology that has the potential to reliably deny law enforcement access to certain data?

The answer will probably remain the same, but acknowledging the problem makes it more powerful. The idea that crypto could not be negotiated about is fundamentalist and therefore wrong. Crypto must be negotiated about and all objective evidence speaks in favor of strong crypto.

Apple, the FBI, and the Omnipotence Paradox

“Can God create a rock so heavy He could not lift it?” this is one version of the omnipotence paradox. To make a long story short, ominpotence as a concept leads to similar logical problems as the naïve set-of-sets and sets-containing-themselves constructions in Russel’s paradox. Some use this paradox to question religion; others use it to question logic; and pondering such questions generally seems to belong to the realm of philosophy. But the ongoing new round of (civil) crypto wars is bringing a tranformed version of this paradox into everyone’s pocket.

Can Apple create an encryption mechanism so strong that even Apple cannot break it? Apple claims so, at least for the particular situation, in their defense against the FBI’s request for help with unlocking a dead terrorist’s iPhone: “As a result of these stronger protections that require data encryption, we are no longer able to use the data extraction process on an iPhone running iOS 8 or later.” Although some residual risk of unknown vulnerabilities remains, this claim seems believable as far as it concerns retroactive circumvention of security defenses. Just as a locksmith can make a lock that will be as hard to break for its maker as for any other locksmith, a gadgetsmith can make gadgets without known backdoors or weaknesses that this gadgetsmith might exploit. This is challenging, but possible.

However, the security of any encryption mechanism hinges on the integrity of key components, such as the encryption algorithm, its implementation, auxiliary functions like key generation and their implementation, and the execution environment of these functions. The maker of a gadget can always weaken it for future access.

Should Apple be allowed to make and sell devices with security mechanisms so strong that neither Apple nor anyone else can break or circumvent them in the course of legitimate investigations? This is the real question here, and a democratic state based on justice and integrity has established institutions and procedures to come to a decision and enforce it. As long as Apple does not rise above states and governments, they will have to comply with laws and regulations if they are not to become the VW of Silicon Valley.

Thus far we do not understand very well how to design systems that allow legitimate law enforcement access while also keeping data secure against illiegitimate access and abuse or excessive use of legitimate means. Perhaps in the end we will have to conclude that too much security would have to be sacrificed for guaranteed law enforcement access, as security experts warn almost in unison, or that a smartphone is too personal a mind extension for anyone to access it without its user’s permission. But this debate we must have: What should the FBI be allowed to access, what would be the design implications of guaranteed access requirements, and which side effects would we need to consider?

For all we know, security experts have a point warning about weakening what does already break more often than not. To expectat that companies could stand above the law because security, however, is just silly.

PS, remember Clarke’s first law: “When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.”

PPS: Last Week Tonight with John Oliver: Encryption

Eat Less Bread?

“Eat less bread” requests a British poster from WWI. We all know it makes sense, don’t we? Resources become scarce at wartime, so wasting them weakens one’s own position. Yet this kind of advice can be utterly useless: tell a hungry person to eat less bread and you will earn, at best, a blank stare. However reasonable your advice may seem to you and everyone else, a hungry person will be physically and mentally unable to comply.

“Do not call system()” or “Do not read uninitialized memory” request secure coding guides. Such advice is equally useless if directed at a person who lacks the cognitive ability to comply. Cognitive limitations do not mean a person is stupid. We all are limited in our respective ability to process information, and we are more similar to than dissimilar from each other in this regard.

Secure coding guidelines all too often dictate a large set of arbitrary dos and don’ts, but fail to take human factors into account. Do X! Don’t do Y, do Z instead! Each of these recommendations has a sound technical basis; code becomes more secure if everyone follows this advice. However, only some of these recommendations are realistic for programmers to follow. Their sheer number should raise our doubt and let us expect that only a subset will ever be adopted by a substantial number of programmers.

Some rules are better suited for adoptions than others. Programmers often acquire idioms and conventions they perceive as helpful. Using additional parentheses for clarity, for example, even though not strictly necessary, improves readability; and the const == var convention prevents certain defects that are easy to introduce and sometimes hard to debug.

Other rules seem, from a programmer’s point of view, just ridiculous. Why is there a system() function in the first place if programmers are not supposed to use it? And if developers should not read uninitialized memory, what would warn them about memory being not initialized? Such advice is inexpensive – and likely ineffective. If we want programmers to write secure code, we must offer them platforms that make secure programming easy and straightforward and insecure programming hard and difficult.

Security and protection systems guard persons and property against a broad range of hazards, including crime; fire and attendant risks, such as explosion; accidents; disasters; espionage; sabotage; subversion; civil disturbances; bombings (both actual and threatened); and, in some systems, attack by external enemies. Most security and protection systems emphasize certain hazards more than others. In a retail store, for example, the principal security concerns are shoplifting and employee dishonesty (e.g., pilferage, embezzlement, and fraud). A typical set of categories to be protected includes the personal safety of people in the organization, such as employees, customers, or residents; tangible property, such as the plant, equipment, finished products, cash, and securities; and intangible property, such as highly classified national security information or “proprietary” information (e.g., trade secrets) of private organizations. An important distinction between a security and protection system and public services such as police and fire departments is that the former employs means that emphasize passive and preventive measures.

(Encyclopædia Britannica)

OMG, public information found world-readable on mobile phones

In their Black Hat stage performance, employees of a security company showed how apps on certain mobile phones can access fingerprint data if the phone has a fingerprint sensor. The usual discussions ensued about rotating your fingerprints, biometrics being a bad idea, and biometric features being usernames rather than passwords. But was there a problem in the first place? Let’s start from scratch, slightly simplified:

  1. Authentication is about claims and the conditions under which one would believe certain claims.
  2. We need authentication when an adversary might profit from lying to us.
  3. Example: We’d need to authenticate banknotes (= pieces of printed paper issued by or on behalf of a particular entity, usually a national or central bank) because adversaries might profit from making us believe  a printed piece of paper is a banknote when it really isn’t.
  4. Authentication per se has nothing to do with confidentiality and secrets, as the banknotes example demonstrates. All features that we might use to authenticate a banknote are public.
  5. What really matters is effort to counterfeit. The harder a feature or set of features is to reproduce for an adversary, the stronger it authenticates whatever it belongs to.
  6. Secrets, such as passwords, are only surrogates for genuine authenticating features. They remain bound to an entity only for as long as any adversary remains uncertain about their choice from a vast space of possible values.
  7. Fingerprints are neither usernames nor passwords. They are (sets of) biometric features. Your fingerprints are as public as the features of a banknote.
  8. We authenticate others by sets of biometric features every day, recognizing colleagues, friends, neigbours, and spouses by their voices, faces, ways of moving, and so on.
  9. We use even weaker (= easier to counterfeit) features to authenticate, for example, police officers. If someone is wearing a police uniform and driving a car with blinkenlights on its roof, we’ll treat this person as a police officer.
  10. As a side condition for successful attack, the adversary must not only be able to counterfeit authenticating features, the adversary must also go through an actual authentication process.
  11. Stolen (or guessed) passwords are so easy to exploit on the Internet because the Internet does little to constrain their abuse.
  12. Attacks against geographically dispersed fingerprint sensors do not scale in the same way as Internet attacks.

Conclusion: Not every combination of patterns-we-saw-in-security-problems makes a security problem. We are leaving fingerprints on everything we touch, they never were and never will be confidential.

Carcinogenic agents classified by evidence

Carcinogenic is a scary word, but what exactly does it mean? The International Agency for Research on Cancer (IARC),  a part of the World Health Organization (WHO), has established a framework. The IACR reviews scientific evidence for and against carcinogenicity claims and places agents in one of the following categories:

  • Group 1 – carcinogenic: Sufficient evidence exists that an agent is carcinogenic in humans. In this group we find, as expected, agents like various forms of radiation (gamma, x-ray, utraviolet), tobacco smoke, alcohol, estrogen-progestogen oral contraceptives, and asbestos.
  • Group 2A – probably carcinogenic: Strong evidence exists that an agent is carcinogenic, yet the evidence rmains insufficient to be sure. More precisely, there is sufficient evidence of carcinogenicity in animals but limited evidence in humans. This group contains, for example, acrylamide and occupational exposure to oxidized bitumens and their emissions during roofing.
  • Group 2B – possibly carcinogenic: Some evidence exists for carcinogenicity of an agent, but it is neither sufficient nor strong. This class comprises agents like chloroform, coffee, DDT, marine diesel fuel, gasoline and gasoline engine exhaust, and certain surgical implants and other foreign bodies.
  • Group 3 – unclassifiable: Evidence is inadequate; the agent may or may not be carcinogenic, we do not know enough to tell. This category contains agents like caffeine, carbon-nanotubes, static or extemely low-frequency electric fields, fluorescent lighting, phenol, polyvinyl chloride, and rock wool.
  • Group 4 – probably not: We have evidence that an agent is not carcinogenic. Perhaps due to publication bias, this group contains only one element, caprolactam.

The IACR publishes classification criteria and lists (by category, alphabetical). Wikipedia also maintains lists by these categories with links to the respective pages.

Keep in mind that this classification represents only the state of evidence regarding cancerogenicity in humans, not your risk of becoming exposed to an agent, a dose-response assessment, or overall health risk from exposure. Hint: everything that kills you quickly and reliably is unlikely to cause you cancer.