Preliminary Program
AtheCrypt will start an hour later, due to the snow!
(*Click on the arrow icon
to view talk details.)| 9:30 - 10:00 | Registration - Opening |
| 10:00 - 10:45 |
Saferandom: Self-Verifiable Raffles from Stock Market values and Bitcoin blocks
Konstantinos Chalkias, Newcrypt
Abstract: Unlike conventional lotteries using ping pong balls or electronic raffles where a randomization algorithm runs internally at a
safe hardware infrastructure, public data that is very difficult to be a-priori predicted has been proposed as an undeniable source of randomness. Some
examples of open data sets that can be used as random beacons include a) the aggregated closing prices of the stocks that comprise an index in the stock
market b) weather conditions such as temperature, wind and humidity at a certain time in the major world capitals c) official flight landing times at biggest
airports and d) the next block in a proof-of-work blockchain, like Bitcoin.
Saferandom is a decentralized, self-verifiable method for conducting raffles, which is tamper-proof and can be verified by anyone from the comfort of his/her home.
The protocol also benefits from the blockchain's inherent support for data ownership proof, document time-stamping and content integrity resulting to a complete
infrastructure that supports secure raffles and transparent statistical sampling.
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| 10:45 - 11:30 |
Laconic Receiver Oblivious Transfer And its Applications
Antigoni Polychroniadou, Aarhus University
Abstract: In this talk, we will introduce a novel technique for secure computation over large inputs. Based on the Decisional Diffie-Hellman (DDH)
assumption, we provide a new Oblivious Transfer (OT) protocol with a laconic receiver. In particular, the laconic OT allows a receiver to commit to a large
input $D$ (of length $m$) via a short message. Subsequently, a single short message by a sender allows the receiver to learn $s_{D_i}$ , where $s_{0}$ , $s_{1}$
and $i \in [m]$ are dynamically chosen by the sender. All prior constructions of OT required the receiver message to grow with $m$.
Such an OT is apt for realizing secure computation over large data. More specifically, we show applications of laconic OT to non-interactive
secure computation and homomorphic encryption for RAM programs.
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| 11:30 - 12:00 | Break |
| 12:00 - 12:45 |
Residue Number System as a Side-Channel Attack Countermeasure for ECC
Louiza Papachristodoulou, iCIS, RU Nijmegen
Abstract: Elliptic Curve Cryptography operations rely heavily on the strong security of scalar multiplication.
However, this operation is vulnerable to side-channel (SCA) and fault injection (FA) attacks. The use of alternative arithmetic systems like Residue Number
System (RNS) for all scalar multiplication underline operations has been proposed as an efficient countermeasure approach for the above attacks. In RNS, a
number is represented as a set of smaller numbers, where each one is the result of the modular reduction with a given moduli basis. Under certain requirements,
a number can be uniquely transformed from the integers to the RNS domain (and vice versa) and all arithmetic operations can be performed in RNS. This representation
provides an inherent SCA and FA resistance to many attacks and can be further enhanced by additional RNS arithmetic manipulations or more traditional algorithmic
countermeasures. In this presentation, I am going to show the potentials of RNS as an SCA and FA countermeasure, provide a description of RNS based SCA and FA
resistance means through appropriate scalar multiplication algorithmic variations and present some practical results from an implementation on an ARM Cortex A7
processor.
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| 12:45 - 13:30 |
Trust Is Risk: A Decentralized Financial Trust Platform
Orfeas Thyfronitis Litos, National Technical University of Athens
Abstract: Reputation in centralized systems uses stars and review-based trust.
Such systems require manual intervention and secrecy to avoid
manipulation. In autonomous and open source decentralized systems this
luxury is not available. Previous peer-to-peer reputation systems do not
allow for financial arguments pertaining to reputation. We propose a
concrete Sybil-resilient decentralized reputation system where direct
trust is defined as lines-of-credit using bitcoin’s 1-of-2 multisig. We
introduce a new model for bitcoin wallets in which user coins are split
among trusted associates. Indirect trust is subsequently defined
transitively. This enables formal game theoretic arguments pertaining to
risk analysis. We prove that risk and max flows are equivalent in our
model. Our system allows for concrete financial decisions on the
monetary amount a pseudonymous party can be trusted with. Through
algorithmic trust redistribution, the risk incurred from making a
purchase from a pseudonymous party in this manner remains invariant.
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| 13:30 - 15:00 | Lunch Break |
| 15:00 - 15:45 |
Reliable Communication with Limited Knowledge
Aris Pagourtzis, National Technical University of Athens
Abstract: TBA
|
| 15:45 - 16:30 |
Location Privacy Through Private Equality Testing
Marios Magioladitis, Ionian University
Abstract: We propose a practical, privacy-preserving equality testing
protocol which allows two users to learn if they share the same
encrypted input data.
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| 16:30 - 17:00 | Break |
| 17:00 - 17:45 |
CTX: Eliminating BREACH with Context Hiding
Dimitris Karakostas, National Technical University of Athens
Abstract: The BREACH attack presented at Black Hat USA 2013 has still not been
mitigated, despite new developments and optimizations presented at Black
Hat Asia 2016. This class of attacks presents itself in all practical web
applications which use compression together with encryption and has not
been fixed in even the most recent versions of TLS 1.3.
In this talk, we present a generic defense method which eliminates
compression-detectability features of existing protocols. We describe CTX,
Context Transformation Extension, a cryptographic method which defends
against BREACH, CRIME, TIME, and generally any compression side-channel
attack. CTX uses context hiding in a per-origin manner to separate secrets
from different origins in order to avoid cross-compressibility. We will
show a demo of the defense and illustrate how it eliminates the attacks.
Our implementation runs at the application layer, is opt-in, and does not
require modifications to web standards or the underlying web server.
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| 17:45 - 18:30 |
Productizing TLS Attacks: The Rupture API
Eva Sarafianou, National Technical University of Athens
Abstract: In this presentation, we extend Rupture, a generic browser TLS side-channel attack framework that was presented in Black Hat Asia 2016,
with a new, open source, usable RESTful API and web interface. We take advantage of the modularity of Rupture to create a robust RESTful API. Our API uses
the existing Rupture modules - the client, injector, sniffer and backend consisting of the strategy and analyzer components - which have high expressibility so
that any side-channel TLS attack such as for example all of CRIME, BREACH, POODLE, TIME, HEIST or BEAST can be implemented.
We will show a demo of the RESTful API and web interface. We will configure a victim and launch a complete BREACH attack against a target in order to illustrate
the automation and usability of the API and the web interface.
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| 18:30 | End |
