Tampering with OpenPGP digitally signed messages by exploiting multi-part messages

The EFAIL vulnerability in the OpenPGP and S/MIME secure email systems, publicly disclosed yesterday, allows an eavesdropper to obtain the contents of encrypted messages. There’s been a lot of finger-pointing as to which particular bit of software is to blame, but that’s mostly irrelevant to the people who need secure email. The end result is that users of encrypted email, who wanted formatting better than what a mechanical typewriter could offer, were likely at risk.

One of the methods to exploit EFAIL relied on the section of the email standard that allows messages to be in multiple parts (e.g. the body of the message and one or more attachments) – known as MIME (Multipurpose Internet Mail Extensions). The authors of the EFAIL paper used the interaction between MIME and the encryption standard (OpenPGP or S/MIME as appropriate) to cause the email client to leak the decrypted contents of a message.

However, not only can MIME be used to compromise the secrecy of messages, but it can also be used to tamper with digitally-signed messages in a way that would be difficult if not impossible for the average person to detect. I doubt I was the first person to discover this, and I reported it as a bug 5 years ago, but it still seems possible to exploit and I haven’t found a proper description, so this blog post summarises the issue.

The problem arises because it is possible to have a multi-part email where some parts are signed and some are not. Email clients could have adopted the fail-safe option of considering such a mixed message to be malformed and therefore treated as unsigned or as having an invalid signature. There’s also the fail-open option where the message is considered signed and both the signed and unsigned parts are displayed. The email clients I looked at (Enigmail with Mozilla Thunderbird, and GPGTools with Apple Mail) opt for a variant of the fail-open approach and thus allow emails to be tampered with while keeping their status as being digitally signed.

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“The pool’s run dry” – analyzing anonymity in Zcash

Zcash is a cryptocurrency whose main feature is a “shielded pool” that is designed to provide strong anonymity guarantees. Indeed, the cryptographic foundations of the shielded pool are based in highly-regarded academic research. The deployed Zcash protocol, however, allows for transactions outside of the shielded pool (which, from an anonymity perspective, are identical to Bitcoin transactions), and it can be easily observed from blockchain data that the majority of transactions do not use the pool. Nevertheless, users of the shielded pool should be able to treat it as their anonymity set when attempting to spend coins in an anonymous fashion.

In a recent paper, An Empirical Analysis of Anonymity in Zcash, we (George Kappos, Haaroon Yousaf, Mary Maller, and Sarah Meiklejohn) conducted an empirical analysis of Zcash to further our understanding of its shielded pool and broader ecosystem. Our main finding is that is possible in many cases to identify the activity of founders and miners using the shielded pool (who are required by the consensus rules to put all newly generated coins into it). The implication for anonymity is that this activity can be excluded from any attempt to track coins as they move through the pool, which acts to significantly shrink the effective anonymity set for regular users. We have disclosed all our findings to the developers of Zcash, who have written their own blog post about this research.  This work will be presented at the upcoming USENIX Security Symposium.

What is Zcash?

In Bitcoin, the sender(s) and receiver(s) in a transaction are publicly revealed on the blockchain. As with Bitcoin, Zcash has transparent addresses (t-addresses) but gives users the option to hide the details of their transactions using private addresses (z-addresses). Private transactions are conducted using the shielded pool and allow users to spend coins without revealing the amount and the sender or receiver. This is possible due to the use of zero-knowledge proofs.

Like Bitcoin, new coins are created in public “coingen” transactions within new blocks, which reward the miners of those blocks. In Zcash, a percentage of the newly minted coins are also sent to the founders (a predetermined list of Zcash addresses owned by the developers and embedded into the protocol).

Continue reading “The pool’s run dry” – analyzing anonymity in Zcash

Scanning beyond the horizon: long-term planning for cybersecurity and the post-quantum challenge

I recently came across an interesting white paper published by PwC, “A false sense of security? Cyber-security in the Middle East”. This paper is interesting for a number of reasons. Most obviously, I guess, it’s about an area of the world that’s a bit different from that of my immediate experience in the West and which faces many well-reported challenges. Indeed, it seems, as reported in the PwC paper, that companies and governments in the region suffer from more cyberattacks, resulting in bigger financial losses, than anywhere else in the world.

The paper confirms that many of the problems faced by companies and governments in the Middle East are, as of course one would expect, exactly those faced by their Western counterparts – too often, the cybersecurity industry responds to incidents in a fire-fighting style, rolling out patches in rushed knee-jerk reactions to imminent threats.

The way to counteract these problems is, of course, to train cybersecurity professionals who will be capable of making appropriate strategic and tactical investments in security and able to respond to respond better to attacks. All well and good, but there is global skills deficit in the cybersecurity industry and it seems that this problem is particularly acute in the Middle East;  and it seems to be a notable contributory factor to the problems experienced in the region. The problem needs some long-term thinking: in the average user, we need to encourage good security behaviours, which are learned over many years; in the security profession, we need to ensure that there is sufficient upcoming talent to fill our growing needs over the next century.

Exploring this topic a bit, I came across a company called SiConsult, a security services provider (with which I have no personal connection), with offices in the Middle East. They are taking an initiative, which provides students (or, indeed, anyone I think) with an interesting opportunity. They have been thinking about cryptography in the post-quantum world, and how to develop solutions and relevant expertise in the long term.

All public key cryptography as we currently know it may be rendered insecure by the deployment of quantum computers. Your Internet connection to the bank, the keys protecting your Dropbox, and your secure messaging applications will all be compromised. But a quantum computer that can run Shor’s algorithm, which means large numbers can be factorized in polynomial time, is still maybe ten years away (or five, or twenty, or … ). So why should we care now? Well, the consequences of losing the protection of good public-key crypto would be very serious and, consequently, NIST (the US’s National Institute of Standards and Technology) is running a process to standardize quantum-resistant algorithms. The first round of submissions has just closed, but we will have to wait until 2025 for draft standards, which could be too late for some use cases.

As a result of the process timeline, companies and academics are likely to search for their own solutions long before NIST standardizes theirs. SiConsult, the company I mentioned, is inviting students (or anyone else) develop a quantum-safe application messaging application, for a small prize – the Post Quantum Innovation Challenge. What is interesting is that the company’s motivation here is not purely financial – they are not looking to retain ownership of any designs or applications that may be submitted to the competition – but instead they are looking to spark interest in post-quantum cryptography, search for new cybersecurity talent, and encourage cybersecurity education, especially in the Middle East.

Initiatives like the Post Quantum Innovation Challenge are needed to energise those that may be considering a career in cyber security, to make sure that the talent pipeline is flowing well for years to come. Importantly, the barrier for entry to PQIC is relatively low: anyone with an interest in security should consider entering. Perhaps it will go a little of the way towards a solution to both the quantum and education long-term problems.

Incentives in Security Protocols

The 2018 edition of the International Security Protocols Workshop took place last week. The theme this year was “fail-safe and fail-deadly concepts in protocol design”.

One common theme at this year’s workshop is that of threat models and incentives, which is covered by the majority of accepted papers. One of these is our (Sarah Azouvi, Alexander Hicks and Steven Murdoch) submission – Incentives in Security Protocols. The aim of the paper is to discuss how incentives can be considered and incorporated in the security of systems. In line with the given theme, the focus is on fail-safe and fail-deadly cases which we look at for the cases of the EMV protocol, consensus in cryptocurrencies, and non-economic systems such as Tor. This post will summarise the main ideas laid out in the paper.

Fail safe, fail deadly and people

Systems can fail, which requires some thought by system designers to account for these failures. From this setting comes the idea behind fail safe protocols which are such that even if the protocol fails, the failure can be dealt with or the protocol can be aborted to limit damage. The idea of a fail deadly setting is an extension of this where failure is defended against through deterrence, as in the case of nuclear deterrence (sometimes a realistic case).

Human input often plays a role in the use of the system, particularly when decisions are required as in fail safe and fail deadly instances. These decisions are then made according to incentives which can aligned to make the system robust to failure. For a fail deadly alignment, this means that a person in position to prevent system failure will be harmed by the failure. In the fail safe case, the innocent parties should be protected from the consequences of system failure. The two concepts are really two sides of the same coin that assigns liability.

It is often said that people are the weakest link in security, but that is an easy excuse for broken protocols. If security incentives are aligned properly, then humans are the strongest link.

The EMV protocol, adding incentives after the fact

As a first example, we consider the case of the EMV protocol, which is used for the majority of smart card payments worldwide, as well as smartphone and card-based contactless payment. Over the years, many vulnerabilities have been identified and removed. Fraud still exists however, due not to unexpected protocol vulnerabilities but to decisions made by banks (e.g., omitting the ability for cards to produce digital signatures), merchants (e.g., omitting PIN verification) and payment networks not sending transactions details back to banks. These are intentional choices, aiming to saves costs and cut transaction times but make fraud harder to detect.

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“Wow such genetics. So data. Very forever?” – An overview of the blockchain genomics trend

In 2014, Harvard professor and geneticist George Church said: “‘Preserving your genetic material indefinitely’ is an interesting claim. The record for storage of non-living DNA is now 700,000 years (as DNA bits, not electronic bits). So, ironically, the best way to preserve your electronic bitcoins/blockchains might be to convert them into DNA”. In early February 2018, Nebula Genomics, a blockchain-enabled genomic data sharing and analysis platform, co-founded by George Church, was launched. And they are not alone on the market. The common factor between all of them is that they want to give the power back to the user. By leveraging the fact that most companies that currently offer direct-to-consumer genetic testing sell data collected from their customers to pharmaceutical and biotech companies for research purposes, they want to be the next Uber or Airbnb, with some even claiming to create the Alibaba for life data using the next-generation artificial intelligence and blockchain technologies.

Nebula Genomics

Its launch is motivated by the need of increasing genomic data sharing for research purposes, as well as reducing the costs of sequencing on the client side. The Nebula model aims to eliminate personal genomics companies as the middle-man between the customer and the pharmaceutical companies. This way, data owners can acquire their personal genomic data from Nebula sequencing facilities or other sources, join the Nebula network and connect directly with the buyers.
Their main claims from their whitepaper can be summarized as follows:

  • Lower the sequencing costs for customers by joining the network to profiting from directly by connecting with data buyers if they had their genomes sequenced already, or by participating in paid surveys, which can incentivize data buyers to subsidize their sequencing costs
  • Enhanced data protection: shared data is encrypted and securely analyzed using Intel Software Guard Extensions (SGX) and partially homomorphic encryption (such as the Paillier scheme)
  • Efficient data acquisition, enabling data buyers to efficiently acquire large genomic datasets
  • Being big data ready, by allowing data owners to privately store their data, and introducing space efficient data encoding formats that enable rapid transfers of genomic data summaries over the network

Zenome

This project aims to ensure that genomic data from as many people as possible will be openly available to stimulate new research and development in the genomics industry. The founders of the project believe that if we do not provide open access to genomic data and information exchange, we are at risk of ending up with thousands of isolated, privately stored collections of genomic data (from pharmaceutical companies, genomic corporations, and scientific centers), but each of these separate databases will not contain sufficient data to enable breakthrough discoveries. Their claims are not as ambitious as Nebula, focusing more on the customer profiting from selling their own DNA data rather than other sequencing companies. Their whitepaper even highlights that no valid solutions currently exist for the public use of genomic information while maintain individual privacy and that encryption is used when necessary. When buying ZNA tokens (the cryptocurrency associated with Zenome), one has to follow a Know-Your-Customer procedure and upload their ID/Passport.

Gene Blockchain

The Gene blockchain business model states it will use blockchain smart contracts to:

  • Create an immutable ledger for all industry related data via GeneChain
  • Offer payment for industry related services and supplies through GeneBTC
  • Establish advanced labs for human genome data analysis via GeneLab
  • Organize and unite global platform for health, entertainment, social network and etc. through GeneNetwork

Continue reading “Wow such genetics. So data. Very forever?” – An overview of the blockchain genomics trend

Coconut: Threshold Issuance Selective Disclosure Credentials with Applications to Distributed Ledgers

Selective disclosure credentials allow the issuance of a credential to a user, and the subsequent unlinkable revelation (or ‘showing’) of some of the attributes it encodes to a verifier for the purposes of authentication, authorisation or to implement electronic cash. While a number of schemes have been proposed, these have limitations, particularly when it comes to issuing fully functional selective disclosure credentials without sacrificing desirable distributed trust assumptions. Some entrust a single issuer with the credential signature key, allowing a malicious issuer to forge any credential or electronic coin. Other schemes do not provide the necessary re-randomisation or blind issuing properties necessary to implement modern selective disclosure credentials. No existing scheme provides all of threshold distributed issuance, private attributes, re-randomisation, and unlinkable multi-show selective disclosure.

We address these challenges in our new work Coconut – a novel scheme that supports distributed threshold issuance, public and private attributes, re-randomization, and multiple unlinkable selective attribute revelations. Coconut allows a subset of decentralised mutually distrustful authorities to jointly issue credentials, on public or private attributes. These credentials cannot be forged by users, or any small subset of potentially corrupt authorities. Credentials can be re-randomised before selected attributes being shown to a verifier, protecting privacy even in the case all authorities and verifiers collude.

Applications to Smart Contracts

The lack of full-featured selective disclosure credentials impacts platforms that support ‘smart contracts’, such as Ethereum, Hyperledger and Chainspace. They all share the limitation that verifiable smart contracts may only perform operations recorded on a public blockchain. Moreover, the security models of these systems generally assume that integrity should hold in the presence of a threshold number of dishonest or faulty nodes (Byzantine fault tolerance). It is desirable for similar assumptions to hold for multiple credential issuers (threshold aggregability). Issuing credentials through smart contracts would be very useful. A smart contract could conditionally issue user credentials depending on the state of the blockchain, or attest some claim about a user operating through the contract—such as their identity, attributes, or even the balance of their wallet.

As Coconut is based on a threshold issuance signature scheme, that allows partial claims to be aggregated into a single credential,  it allows collections of authorities in charge of maintaining a blockchain, or a side chain based on a federated peg, to jointly issue selective disclosure credentials.

System Overview

Coconut is a fully featured selective disclosure credential system, supporting threshold credential issuance of public and private attributes, re-randomisation of credentials to support multiple unlikable revelations, and the ability to selectively disclose a subset of attributes. It is embedded into a smart contract library, that can be called from other contracts to issue credentials. The Coconut architecture is illustrated below. Any Coconut user may send a Coconut request command to a set of Coconut signing authorities; this command specifies a set of public or encrypted private attributes to be certified into the credential (1). Then, each authority answers with an issue command delivering a partial credentials (2). Any user can collect a threshold number of shares, aggregate them to form a consolidated credential, and re-randomise it (3). The use of the credential for authentication is however restricted to a user who knows the private attributes embedded in the credential—such as a private key. The user who owns the credentials can then execute the show protocol to selectively disclose attributes or statements about them (4). The showing protocol is publicly verifiable, and may be publicly recorded.

 

Implementation

We use Coconut to implement a generic smart contract library for Chainspace and one for Ethereum, performing public and private attribute issuing, aggregation, randomisation and selective disclosure. We evaluate their performance, and cost within those platforms. In addition, we design three applications using the Coconut contract library: a coin tumbler providing payment anonymity, a privacy preserving electronic petitions, and a proxy distribution system for a censorship resistance system. We implement and evaluate the first two former ones on the Chainspace platform, and provide a security and performance evaluation. We have released the Coconut white-paper, and the code is available as an open-source project on Github.

Performance

Coconut uses short and computationally efficient credentials, and efficient revelation of selected attributes and verification protocols. Each partial credentials and the consolidated credential is composed of exactly two group elements. The size of the credential remains constant, and the attribute showing and verification are O(1) in terms of both cryptographic computations and communication of cryptographic material – irrespective of the number of attributes or authorities/issuers. Our evaluation of the Coconut primitives shows very promising results. Verification takes about 10ms, while signing an attribute is 15 times faster. The latency is about 600 ms when the client aggregates partial credentials from 10 authorities distributed across the world.

Summary

Existing selective credential disclosure schemes do not provide the full set of desired properties needed to issue fully functional selective disclosure credentials without sacrificing desirable distributed trust assumptions. To fill this gap, we presented Coconut which enables selective disclosure credentials – an important privacy enhancing technology – to be embedded into modern transparent computation platforms. The paper includes an overview of the Coconut system, and the cryptographic primitives underlying Coconut; an implementation and evaluation of Coconut as a smart contract library in Chainspace and Ethereum, a sharded and a permissionless blockchain respectively; and three diverse and important application to anonymous payments, petitions and censorship resistance.

 

We have released the Coconut white-paper, and the code is available as an open-source project on GitHub.  We would be happy to receive your feedback, thoughts, and suggestions about Coconut via comments on this blog post.

The Coconut project is developed, and funded, in the context of the EU H2020 Decode project, the EPSRC Glass Houses project and the Alan Turing Institute.

Thinking about fake news – As a security incident?

In Tristan and David’s Philosophy, Politics and Economics of Security and Privacy class, Jono gave a little information about incident response.  As a result, we have been thinking about the recent furor over fake news. There are some big questions circling this topic, and we’re going to try to focus on a part we have some competence in: what an understanding of fake news as a security incident can contribute to the wider debate. Our goal here is mostly to highlight some lessons from security research that should be applicable, so we can help constrain the solution space. Ultimately, any solution will need to engage with wider civil society.

The lessons we will argue for in the following are:

  • Solutions need to support the elector’s primary task. Education to avoid cognitive biases is not a short- or medium-term solution.
  • Focus on aligning the incentives of the media companies and the voters. Reduce the return on investment for the adversary.
  • Any blocking should be strategically useful, and not merely reactionary.

First, we want a more specific term, as well as a less charged one. Fake news includes politically or financially motivated stories presented as factual reports on the world that are fictional in material ways, and usually are intended to stir strong feelings. This definition is hardly complete. Furthermore, similar to the term “post-truth” as discussed by Jasanoff and Simmet, the term “fake news” makes several value judgement we’d like to avoid. “Fake news” carries a strong suggestion that we, the speakers, know what is true and what isn’t, and it also indicates some condescension by the speaker for anyone who believes an item of fake news. We want to avoid such insults. Instead, let’s say we want to focus on the following hypothetical security policy: democratic elections should be free from foreign interference.

Grounding out this policy definition hangs on the term “interference.” This is hard. Ultimately, the will of an elector in a free and fair election needs to be respected. This makes it particularly challenging to agree on constraints to what information an elector has access to. In practice, no elector is omniscient, so some constraints de facto exist. But weighing in on this issue is outside our competence. Let’s assume for now that public policy will provide an assessment of “interference” eventually. The UK recently announced a “dedicated national security communications unit” would be charged with “combating disinformation by state actors and others.” In France, Emmanuel Macron plans legislation to fight interference from foreign sources during elections. Various social media platforms have likewise announced attempted fixes, which means they have some functional definition of what “interference” they’re seeking to remove. Unfortunately, “none of the tech giants claim to be ready” for the November 2018 elections in the US.

Interference in elections is a type of information warfare. An appropriate security policy needs to assess the threat environment and the capabilities of the adversaries. In particular, the Russian Federation has been assessed as a highly motivated and well-resourced actor in this space. We should note that Russia, in turn, assesses the intent and capability of the USA similarly. Tools and tactics within information warfare, particularly disinformation campaigns, help define “interference” within our security policy.

In this context, what can the security research community recommend? Well, the main target of the disinformation campaign are usual citizens. They are targetable largely due to inherent cognitive biases in the way humans process and reason about information. In security terms, we could see these biases as vulnerabilities in the system. Classically, we have two options to secure the system: patch the vulnerability, or prevent the adversary from exploiting it by controlling or filtering the attack before it reaches the target.

Patch in this case would mean teaching people to avoid cognitive biases in their day-to-day reasoning. Psychology tells us this is hard. Intelligence analysts train for months or years for this. And the research in usable security has affirmed time and time again that the users are not the enemy. That is, the system must alleviate the burden on the user’s attention and not interfere with their primary task, or else the user will subvert or avoid the protections put in place. Any changes in user culture are slow. This leads us to lesson 1 on preventing disinformation campaigns for election interference: solutions need to support the elector’s primary task. Education to avoid cognitive biases is not a short-term or medium-term solution.

Controlling the attack vectors is more promising, although filtering them is not. A key aspect of any information security policy is aligning the economic incentives of the actors. Economics is a main reason why infosec is hard. It may not be easy to reorganize the incentives in the advertising and news distribution media space. However, as long as organizations profit from more clicks on an article no matter the content, there will be an incentive to drive viewers that is ultimately at cross-purposes with our security goal. Such misaligned incentives often swamp any technical security solutions. And any adversary with an economic incentive to attack usually will. Thus our second lesson: focus on aligning the incentives of the media companies and the voters; reduce the return on investment for the adversary. Exactly how to do these things will require future work.

There are huge issues about human rights and free speech for blocking access to information. However, the technical aspects of blacklisting are worth understanding before even attempting such human-rights debates. Blacklists of internet resources, such as domain names, IP addresses, or web pages, are useful. But they’re not a final solution. Whether blacklists move at the speed of national legislatures or are updated every five minutes, their main impact is to cause the adversary to move around.  Blacklists alone are not enough. We would need to look for suspiciously mobile resources (i.e. fast-flux), and eventually whitelist resources. Blacklists such as implemented by Facebook in response to Congress are helpful. But we should carefully consider how they drive the disinformation campaigns into a place we are better able to counteract them, and be sure we don’t make such campaigns harder to find instead. Lesson 3 is therefore that any blocking should be strategically useful, and not merely reactionary.

We’d be happy for further comments on fake news, disinformation campaigns that interfere with elections, lessons we’ve missed, disagreements about the value of security research to this topic, and other comments you might have! This is a wide open topic, and we’re still sounding it all out.

A witch-hunt for trojans in our chips

A Hardware Trojan (HT) is a malicious modification of the circuitry of an integrated circuit.

 

A malicious chip can make a device malfunction in several ways. It has been rumored that a hardware trojan implanted in a Syrian air-defense radar caused it to stop operating during an airstrike, thus instantly minimizing the country’s situational awareness and threat response capabilities. In other settings, hardware trojans may leak encryption keys or other secrets, or even generate weak keys that can be easily recovered by the adversary.

This article introduces a new trojan-resilient architecture, discusses its motivation and outlines how it differs from existing solutions. The full paper (Vasilios MavroudisAndrea CerulliPetr Svenda, Dan CvrcekDusan Klinec, George Danezis) has been presented in several academic and industrial venues including DEF CON 25, and ACM Conference on Computer and Communications Security 2017.

The Challenge of Detecting HT

Judging from the abundance of governmental, industrial and academic projects concerned with the prevention and the detection of hardware trojans, there is a consensus regarding the severity of the threat and it’s not taken lightly. DARPA has launched the “Integrity and Reliability of Integrated Circuits“ program aiming to develop techniques for the detection of malicious circuitry. The Intelligence Advanced Research Projects Activity funded a project aiming to redesign the fabrication of integrated circuits, while various other initiatives are currently undergoing (e.g., the COST Action project on “Trustworthy Manufacturing and Utilization of Secure Devices” and the DoD Trusted Foundry program). In addition to these, there are numerous other industrial and academic projects proposing new trojan detection techniques every year, only to be circumvented by follow up work.

But do Hardware Trojans exist?

Ironically, until now there have been no cases where malicious circuitry was detected in military-grade or even commercial chips. With nothing more than rumors to hint about hardware trojans (in places other than academic lab benches), one cannot but question their existence. In other words, is HT design and insertion too complex to be practical, or do our detection tools fail to detect the malicious circuitry embedded in the chips around us?

It could be that both are true: hardware trojans do not exist (yet) as malicious actors are focusing on other aspects of the hardware that are easier to compromise. In all cases where trojans were discovered, the erroneous behavior was traced to the chip’s firmware and not its circuitry. Interestingly, in the vast majority of those incidents the security flaws were attributed to honest fabrication mistakes (e.g., manufacturer failing to disable a testing interface).

Intentional vs. Unintentional Errors

It is safe to always assume that an IC will fail in the worst possible way, at the worst possible time (see Syrian airdefense incident). This “crash n’ burn” approach is common in critical systems (e.g., airplanes, satellites, dams), where any divergence from normal operation will result in an irrecoverable failure of the whole system.

To mitigate the risk, critical system designers employ redundancy techniques to eliminate single points of failure and thus make their setups resilient to faults. A common example are triple-redundant systems used in autopilots. Those systems employ three identical chips sourced from disjoint supply chains and replicate all the navigation computations across them. This allows the system to both tolerate a misbehaving chip and detect its presence.

It is noteworthy, that those systems do not consider the cause of the chip malfunction, and simply assume that they fail in the worst possible way. Following from this, a malicious chip is not significantly different from a defective one. After all, any adversary sophisticated enough to design and insert a hardware trojan is capable of making it indistinguishable from honest manufacturing errors. Similarly, from an operational perspective it makes little sense to distinguish between trojans in the circuitry and trojans in the firmware as the risk they pose for the system is identical.

Distributing Trust for Resilience

Given that it is impossible to achieve 100% detection rates of hardware trojans and errors, it is important that our devices maintain their security properties even in their presence. Our work introduces a new high-level device architecture that is resilient to both. In its core, it uses a redundancy-based architecture and secret-sharing protocols to distribute all secrets and computations among multiple chips. Hence, unless all chips are compromised by the same adversary, the security of the system remains intact. A key point is that those chips should originate from disjoint supply chains. This is to minimize the risk of the same adversary compromising more than one chips. To evaluate its practicality in real-life applications, we built a Hardware Security Module (HSM) that performs standard cryptographic operations (e.g., key generation, decryption, signing) at a very high rate. HSMs are commonly used in operations where security is critical, and an increased transaction throughput is needed (e.g., banking, certification Authorities). A demonstration is shown in the video above, and further details are on our website. Finally, our work can be easily combined with all existing detection and prevention techniques to further decrease the likelihood of compromises.

An investigation of online censorship in Cyprus

The island of Cyprus, situated in the east of the Mediterranean sea, has always been an important commercial and information exchange hub. Today, this is reflected on the large number of submarine cables that facilitate telecommunications with neighboring countries (Greece, Turkey, Egypt, Israel, Syria, and Lebanon) and with the rest of the world (reaching as far as India, South Korea, and Australia). Nevertheless, the Republic of Cyprus (RoC) is officially regarded as a freedom of expression safe haven, where “Internet is completely free of any specific regulation”. Unfortunately, Cypriot netizens claim that such statements couldn’t be further from the truth.

In recent years, Internet Service Providers (ISPs) in RoC have implemented an Internet filtering infrastructure to comply with the laws and regulations implied by the National Betting Authority (NBA). In an effort to understand the capacity of this infrastructure, a multi-disciplinary group of volunteers from the hack66 Observatory in Nicosia has collected and analyzed connectivity measurements from end-user connections on a variety of websites and services. Their report was presented at the 7th International Conference on e-Democracy.

For their experiments, the hack66 Observatory team put together a testlist comprising of domains from the National Betting Authority blocklist, the CitizenLab lists for Greece and Turkey, and WordPress blogs banned in Turkey as reported at the Lumen Database. The analysis was based on over 45,000 measurements from four residential ISPs operating in the Republic of Cyprus, that were anonymously submitted using a custom OONI probe during the months of March to May 2017. In addition, the team collected data using open DNS resolvers in Cyprus. Early findings suggest that the most common blocking method is DNS hijacking. Furthermore, the measurements indicate that some of the ISPs have deployed middle-boxes – network components capable of performing censorship, traffic manipulation or surveillance.

A closer inspection on the variations of the censorship mechanism implementations among ISPs raised concerns with regard to transparency and privacy: some ISPs do not inform users why a blocked website is not accessible; while others redirect requests to a web server controlled by the NBA, that could in turn log user identifiers such as their IP address. Similarly, the hack66 Observatory team was able to identify a number of unreported Internet censorship cases, entries in the NBA blocklist that either are invalid or that require sophisticated blocking techniques, and collateral damage due to blocking of email delivery to the regulated domains.

Understanding the case of Internet freedom in Cyprus becomes more complicated when the geopolitical situation is taken into consideration. Apart from the Republic of Cyprus, the island of Cyprus is divided into three other segments: the self-declared Turkish Republic of Northern Cyprus; the United Nations-controlled Green Line buffer zone; and the Sovereign Base Areas of Akrotiri and Dhekelia that remain under British control for military purposes. Measurements from the Multimax ISP operating in the area occupied by Turkey indicate network interference practices similar to those of mainland Turkey. This could be interpreted as the existence of two distinct regimes in terms of information policy on the island of Cyprus. No volunteers submitted measurements from the UN buffer zone or the British Sovereign bases. However, it is known via the Snowden revelations that GCHQ is operating a wiretap base in Cyprus codenamed “SOUNDER”, jointly funded by the NSA.

The purpose of the hack66 Observatory is to “to collect and analyze data, and routes of data through EMEA, […] in order to promote evidence based policy making”. The timing is just right, given the recent RoC government announcement of a new bill in the making, to regulate media operations and stop fake news. With their report, the hack66 Observatory aims to provide policy makers with a valuable asset for understanding the limitations and implications of the existing censorship infrastructure, and to start a debate around Internet freedom on the entirety of the island of Cyprus.

Smart Contracts and Bribes

We propose smart contracts that allows a wealthy adversary to rent existing hashing power and attack Nakamoto-style consensus protocols. Our bribery smart contracts highlight:

  • The use of Ethereum’s uncle block reward to directly subsidise a bribery attack,
  • The first history-revision attack requiring no trust between the briber and bribed miners.
  • The first realisation of a Goldfinger attack, using a contract that rewards miners in one cryptocurrency (e.g. Ethereum) for reducing the utility of another cryptocurrency (e.g. Bitcoin).

This post provides an overview of the full paper (by Patrick McCorry, Alexander Hicks and Sarah Meiklejohn) which will be presented at the 5th Workshop on Bitcoin and Blockchain Research, held at this year’s Financial Cryptography and Data Security conference.

What is a bribery attack?

Fundamentally, a wealthy adversary (let’s call her Alice) wishes to manipulate the blockchain in some way. For example, by censoring transactions, revising the blockchain’s history or trying to reduce the utility of another blockchain.

But purchasing hardware up front and competing with existing miners is discouragingly expensive, and may require a Boeing or two. Instead, it may be easier and more cost-effective for Alice to temporarily rent hashing power and obtain a majority of the network’s hash rate before performing the attack.

Continue reading Smart Contracts and Bribes