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Producing Trustworthy Hardware Using Untrusted Components, Personnel and Resources
Computer security is a full-system property, and attackers will always
go after the weakest link in a system. In modern computer systems,
the hardware supply chain is an obvious and vulnerable point of
attack. The ever-increasing complexity of hardware systems, along with
the globalization of the hardware supply chain, has made it unreasonable
to trust hardware. Hardware-based attacks, known as backdoors, are easy
to implement and can undermine the security of systems built on top of
compromised hardware. Operating systems and other software can only be
secure if they can trust the underlying hardware systems.
The full supply chain for creating hardware includes multiple processes,
which are often addressed in disparate threads of research, but which we
consider as one unified process. On the front-end side, there is the soft
design of hardware, along with validation and synthesis, to ultimately
create a netlist, the document that defines the physical layout of
hardware. On the back-end side, there is a physical fabrication process,
where a chip is produced at a foundry from a supplied netlist, followed
in some cases by post-fabrication testing. Producing a trustworthy chip
means securing the process from the early design stages through to the
post-fabrication tests.
We propose, implement and analyze a series of methods for making
the hardware supply chain resilient against a wide array of known and
possible attacks. These methods allow for the design and fabrication of
hardware using untrustworthy personnel, designs, tools and resources,
while protecting the final product from large classes of attacks, some
known previously and some discovered and taxonomized in this work.
The overarching idea in this work is to take a full-process view of
the hardware supply chain. We begin by securing the hardware design and
synthesis processes uses a defense-in-depth approach. We combine this
work with foundry-side techniques to prevent malicious modifications
and counterfeiting, and finally apply novel attestation techniques to
ensure that hardware is trustworthy when it reaches users.
For our design-side security approach, we use defense-in-depth
because in practice, any security method can potentially subverted, and
defense-in-depth is the best way to handle that assumption. Our approach
involves three independent steps. The first is a functional analysis
tool (called FANCI), applied statically to designs during the coding and
validation stages to remove any malicious circuits. The second step is
to include physical security circuits that operate at runtime. These
circuits, which we call trigger obfuscation circuits, scramble data at
the microarchitectural level so that any hardware backdoors remaining in
the design cannot be triggered at runtime. The third and final step is to
include a runtime monitoring system that detects any backdoor payloads
that might have been achieved despite the previous two steps. We design
two different versions of this monitoring system. The first, TrustNet, is
extremely lightweight and protects against an important class of attacks
called emitter backdoors. The second, DataWatch, is slightly more heavyweight
(though still efficient and low overhead) that can catch a wider variety
of attacks and can be adapted to protect against nearly any type of
digital payload. We taxonomize the types of attacks that are possible
against each of the three steps of our defense-in-depth system and show
that each defense provides strong coverage with low (or negligible)
overheads to performance, area and power consumption.
For our foundry-side security approach, we develop the first foundry-side
defense system that is aware of design-side security. We create a
power-based side-channel, called a beacon. This beacon is essentially a
benign backdoor. It can be turned on by a special key (not provided to
the foundry), allowing for security attestation during post-fabrication
testing. By designing this beacon into the design itself, the beacon
requires neither keys nor storage, and as such exists in the final chip
purely by virtue of existing in the netlist. We further obfuscate the
netlist itself, rendering the task of reverse engineering the beacon
(for a foundry-side adversary) intractable. Both the inclusion of the
beacon and the obfuscation process add little to area and power costs
and have no impact on performance.
All together, these methods provide a foundation on which hardware
security can be developed and enhanced. They are low overhead and
practical, making them suitable for inclusion in next generation
hardware. Moving forward, the criticality of having trustworthy hardware
can only increase. Ensuring that the hardware supply chain can be trusted
in the face of sophisticated adversaries is vital. Both hardware design
and hardware fabrication are increasingly international processes, and
we believe continuing with this unified approach is the correct path
for future research. In order for companies and governments to place
trust in mission-critical hardware, it is necessary for hardware to be
certified as secure and trustworthy. The methods we propose can be the
first steps toward making this certification a reality
Moving target defense for securing smart grid communications: Architectural design, implementation and evaluation
Supervisory Control And Data Acquisition (SCADA) communications are often subjected to various kinds of sophisticated cyber-attacks which can have a serious impact on the Critical Infrastructure such as the power grid. Most of the time, the success of the attack is based on the static characteristics of the system, thereby enabling an easier profiling of the target system(s) by the adversary and consequently exploiting their limited resources. In this thesis, a novel approach to mitigate such static vulnerabilities is proposed by implementing a Moving Target Defense (MTD) strategy in a power grid SCADA environment, which leverages the existing communication network with an end-to-end IP Hopping technique among the trusted peer devices. This offers a proactive L3 layer network defense, minimizing IP-specific threats and thwarting worm propagation, APTs, etc., which utilize the cyber kill chain for attacking the system through the SCADA network. The main contribution of this thesis is to show how MTD concepts provide proactive defense against targeted cyber-attacks, and a dynamic attack surface to adversaries without compromising the availability of a SCADA system.
Specifically, the thesis presents a brief overview of the different type of MTD designs, the proposed MTD architecture and its implementation with IP hopping technique over a Control Center–Substation network link along with a 3-way handshake protocol for synchronization on the Iowa State’s Power Cyber testbed. The thesis further investigates the delay and throughput characteristics of the entire system with and without the MTD to choose the best hopping rate for the given link. It also includes additional contributions for making the testbed scenarios more realistic to real world scenarios with multi-hop, multi-path WAN. Using that and studying a specific attack model, the thesis analyses the best ranges of IP address for different hopping rate and different number of interfaces. Finally, the thesis describes two case studies to explore and identify potential weaknesses of the proposed mechanism, and also experimentally validate the proposed mitigation alterations to resolve the discovered vulnerabilities. As part of future work, we plan to extend this work by optimizing the MTD algorithm to be more resilient by incorporating other techniques like network port mutation to further increase the attack complexity and cost
Wink: Deniable Secure Messaging
End-to-end encrypted (E2EE) messaging is an essential first step towards
combating increasingly privacy-intrusive laws. Unfortunately, it is vulnerable
to compelled key disclosure -- law-mandated, coerced, or simply by device
compromise. This work introduces Wink, the first plausibly-deniable messaging
system protecting message confidentiality even when users are coerced to hand
over keys/passwords. Wink can surreptitiously inject hidden messages in the
standard random coins (e.g., salt, IVs) used by existing E2EE protocols. It
does so as part of legitimate secure cryptographic functionality deployed
inside widely-available trusted execution environments (TEEs) such as
TrustZone. This provides a powerful mechanism for hidden untraceable
communication using virtually unchanged unsuspecting existing E2EE messaging
apps, as well as strong plausible deniability. Wink has been demonstrated with
multiple existing E2EE applications (including Telegram and Signal) with
minimal (external) instrumentation, negligible overheads, and crucially without
changing on-wire message formats
Security of Ubiquitous Computing Systems
The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license
Security of Ubiquitous Computing Systems
The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license
Subliminal Hash Channels
Due to their nature, subliminal channels are mostly regarded as being malicious, but due to recent legislation efforts users\u27 perception might change. Such channels can be used to subvert digital signature protocols without degrading the security of the underlying primitive. Thus, it is natural to find countermeasures and devise subliminal-free signatures. In this paper we discuss state-of-the-art countermeasures and introduce a generic method to bypass them
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