2,955 research outputs found
Combinatorics on words in information security: Unavoidable regularities in the construction of multicollision attacks on iterated hash functions
Classically in combinatorics on words one studies unavoidable regularities
that appear in sufficiently long strings of symbols over a fixed size alphabet.
In this paper we take another viewpoint and focus on combinatorial properties
of long words in which the number of occurrences of any symbol is restritced by
a fixed constant. We then demonstrate the connection of these properties to
constructing multicollision attacks on so called generalized iterated hash
functions.Comment: In Proceedings WORDS 2011, arXiv:1108.341
HashCore: Proof-of-Work Functions for General Purpose Processors
Over the past five years, the rewards associated with mining Proof-of-Work
blockchains have increased substantially. As a result, miners are heavily
incentivized to design and utilize Application Specific Integrated Circuits
(ASICs) that can compute hashes far more efficiently than existing general
purpose hardware. Currently, it is difficult for most users to purchase and
operate ASICs due to pricing and availability constraints, resulting in a
relatively small number of miners with respect to total user base for most
popular cryptocurrencies. In this work, we aim to invert the problem of ASIC
development by constructing a Proof-of-Work function for which an existing
general purpose processor (GPP, such as an x86 IC) is already an optimized
ASIC. In doing so, we will ensure that any would-be miner either already owns
an ASIC for the Proof-of-Work system they wish to participate in or can attain
one at a competitive price with relative ease. In order to achieve this, we
present HashCore, a Proof-of-Work function composed of "widgets" generated
pseudo-randomly at runtime that each execute a sequence of general purpose
processor instructions designed to stress the computational resources of such a
GPP. The widgets will be modeled after workloads that GPPs have been optimized
for, for example, the SPEC CPU 2017 benchmark suite for x86 ICs, in a technique
we refer to as inverted benchmarking. We provide a proof that HashCore is
collision-resistant regardless of how the widgets are implemented. We observe
that GPP designers/developers essentially create an ASIC for benchmarks such as
SPEC CPU 2017. By modeling HashCore after such benchmarks, we create a
Proof-of-Work function that can be run most efficiently on a GPP, resulting in
a more accessible, competitive, and balanced mining market
Formal Computational Unlinkability Proofs of RFID Protocols
We set up a framework for the formal proofs of RFID protocols in the
computational model. We rely on the so-called computationally complete symbolic
attacker model. Our contributions are: i) To design (and prove sound) axioms
reflecting the properties of hash functions (Collision-Resistance, PRF); ii) To
formalize computational unlinkability in the model; iii) To illustrate the
method, providing the first formal proofs of unlinkability of RFID protocols,
in the computational model
Quantum attacks on Bitcoin, and how to protect against them
The key cryptographic protocols used to secure the internet and financial
transactions of today are all susceptible to attack by the development of a
sufficiently large quantum computer. One particular area at risk are
cryptocurrencies, a market currently worth over 150 billion USD. We investigate
the risk of Bitcoin, and other cryptocurrencies, to attacks by quantum
computers. We find that the proof-of-work used by Bitcoin is relatively
resistant to substantial speedup by quantum computers in the next 10 years,
mainly because specialized ASIC miners are extremely fast compared to the
estimated clock speed of near-term quantum computers. On the other hand, the
elliptic curve signature scheme used by Bitcoin is much more at risk, and could
be completely broken by a quantum computer as early as 2027, by the most
optimistic estimates. We analyze an alternative proof-of-work called Momentum,
based on finding collisions in a hash function, that is even more resistant to
speedup by a quantum computer. We also review the available post-quantum
signature schemes to see which one would best meet the security and efficiency
requirements of blockchain applications.Comment: 21 pages, 6 figures. For a rough update on the progress of Quantum
devices and prognostications on time from now to break Digital signatures,
see https://www.quantumcryptopocalypse.com/quantum-moores-law
IMPROVING SMART GRID SECURITY USING MERKLE TREES
Abstract—Presently nations worldwide are starting to convert their aging electrical power infrastructures into modern, dynamic power grids. Smart Grid offers much in the way of efficiencies and robustness to the electrical power grid, however its heavy reliance on communication networks will leave it more vulnerable to attack than present day grids. This paper looks at the threat to public key cryptography systems from a fully realized quantum computer and how this could impact the Smart Grid. We argue for the use of Merkle Trees in place of public key cryptography for authentication of devices in wireless mesh networks that are used in Smart Grid applications
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