- Jens-Matthias Bohli, Christian Henrich, Carmen Kempka and Jörn Müller-Quade
"Enhancing Electronic Voting Machines on the Example of Bingo Voting"
IEEE Transactions on Information Forensics and Security, vol. 4, pp. 745-750, 2009
[Abstract]
The main purpose of cryptographic voting schemes is to
provide transparency while protecting ballot secrecy and to enable a fast
tally. In this paper, we address three major issues of cryptographic voting
schemes. First we discuss the problem of secrecy and coercion resistance
in the situation of a corrupted voting machine. While hard to obtain in
general, we propose and analyze a novel approach that uses encapsulated
design and minimizes the information that can compromise ballot secrecy.
The second issue we address is the assumption that an adversary does
not know which receipts are checked and the problem of receipt stealing.
Many voting schemes with receipts share this vulnerability. We provide
a solution that increases protection of each vote and which can be generalized
for voting schemes that use computers to form the receipt. The
last issue discussed in this paper is the question of how an election can be
contested. For this, an error or a manipulation must not only be detected
but also proven. While the problems and solutions are described for Bingo
Voting, we argue that the problems are shared by many cryptographic
voting schemes and that the solutions presented in this work give insight
in the prerequisites needed for a secure election.
- Jens-Matthias Bohli, Alban Hessler, Osman Ugus, Dirk Westhoff
"Security enhanced multi-hop over the air reprogramming with fountain codes"
IEEE SENSEAPP 2009
[Abstract]
Recently, several code update approaches for multi-hop sensor networks have
been proposed basically addressing two orthogonal problems: security and efficient over the
air reprogramming. Unfortunately, the proposed security solutions for code update
mechanisms are only considering early proposed over the air reprogramming solutions like
e.g. Deluge or MOAP. Therefore, currently available
symmetric key based secure code update
schemes are not per se suited to support advanced coding techniques such as Fountain Codes.
In this work, we provide means to secure this promising technique mainly with efficient symmetric cryptographic primitives and demonstrate its applicability for
efficient and robust over the air reprogramming.
- Jens-Matthias Bohli, Christoph Sorge, and Dirk Westhoff
"Initial observations on economics, pricing, and penetration of the internet of things market"
ACM Comput. Commun. Rev. (Editorial Note), vol. 39, no. 2, pp. 50-55, 2009.
[Abstract]
One expectation about the future Internet is the participation of
billions of sensor nodes, integrating the physical with the digital
world. This Internet of Things can offer new and enhanced
services and applications based on knowledge about the environment and
the entities within. Millions of micro-providers could come into
existence, forming a highly fragmented market place with new business
opportunities to offer commercial services.
In the related field of Internet and Telecommunication services, the design of markets and pricing schemes has been a vital
research area in itself. We discuss how these findings can be transferred
to the Internet of Things. Both the appropriate market structure and
corresponding pricing schemes need to be well understood to enable a
commercial success of sensor-based services.
We show some steps that an evolutionary establishment of this market
might have to take.
- Jens-Matthias Bohli and Andreas Pashalidis
"Relations among Privacy Notions"
Financial Cryptography and Data Security, FC'09, Lecture Notes in Computer Science, vol. 5628, pp. 362-380, Springer, 2009.
[Abstract]
[Full Version]
This paper presents a hierarchy of privacy notions that covers
multiple anonymity and unlinkability variants. The underlying definitions,
which are based on the idea of indistinguishability between two
worlds, provide new insights into the relation between, and the fundamental
structure of, different privacy notions. We apply our definitions
to group signatures and anonymous communication systems, and show
how they relate to existing definitions.
- Osman Ugus and Dirk Westhoff and Jens-Matthias Bohli
"A ROM-friendly Secure Code Update mechanism for WSNs using a stateful-verifier T-time Signature Scheme"
ACM Conference on Wireless Network Security, WiSec'09, pp. 29-40, ACM, 2009.
[Abstract]
Several mechanisms have been proposed to efficiently authenticate multicast of finite data streams as needed for code image
updates in wireless sensor networks (WSNs). They involve either a public-key digital signature or loose time synchronization
between the sender and the receivers. What usually does not get any attention is the program memory (ROM) occupied by
these mechanisms which do not fulfill the primary task of a sensor network.
An optimized implementation of the elliptic curve digital signature scheme occupies up to 25%
of the ROM of a TelosB node; the same or even more is needed for time synchronization schemes.
Therefore, if sensor networks do not need public-key operations or time synchronization for their primary task, these
SCU mechanism are not suitable for coexistence with the application code on the sensor nodes. This work contributes in two directions.
Firstly, we propose a stateful-verifier T-time signature scheme based on Merkle's one-time
signature. Secondly, we propose a protocol exploiting our signature scheme for securing existing code image update protocols for
WSNs minimizing ROM overhead to 1% on TelosB motes.
- Emiliano De Cristofaro and Jens-Matthias Bohli and Dirk Westhoff
"FAIR: Fuzzy based Aggregation providing In-network Resilience for real-time Wireless Sensor Networks"
ACM Conference on Wireless Network Security, WiSec'09, pp. 253-260, ACM, 2009.
[Abstract]
This work introduces FAIR, a novel framework for Fuzzy-based
Aggregation providing In-network Resilience for Wireless Sensor Networks (WSN).
FAIR addresses the possibility of malicious aggregator nodes manipulating data. It provides data-integrity based on a trust level of the WSN response
and it tolerates link or node failures.
Compared to available solutions, it offers a general aggregation model and makes the trust level visible to the querier.
We classify the proposed approach as
complementary to protocols ensuring resilience against sensor leaf nodes providing faulty data.
Thanks to our flexible resilient framework and due to the use of Fuzzy Inference Schemes, we achieve promising results
within a short design cycle.
- Jens-Matthias Bohli and Christoph Sorge
"Key-Substitution-Angriffe und das Signaturgesetz"
Datenschutz und Datensicherheit, vol. 32, no. 6, pp. 388-393, 2008
[Abstract]
Der vorliegende Beitrag widerlegt die gängige Annahme, nahezu jedes kryptographische Signaturverfahren
erfülle die Anforderungen an fortgeschrittene elektronische Signaturen.
Auch Algorithmen, die nach üblichen Kriterien der Kryptographie als sicher bezeichnet werden,
werden den Anforderungen des Gesetzgebers nicht gerecht. Key-Substitution-Angriffe
gefährden auch heute übliche Signaturalgorithmen. Der Artikel geht auch auf Gegenmaßnahmen
ein und betrachtet Folgen für die qualifizierte Signatur.
- Jens-Matthias Bohli, Alban Hessler, Osman Ugus, and Dirk Westhoff
"A Secure and Resilient WSN Roadside Architecture for Intelligent Transport
Systems"
ACM Conference on Wireless Network Security, WiSec '08, pp. 161-171, ACM, 2008
[Abstract]
We propose a secure and resilient WSN roadside architec-
ture for intelligent transport systems which supports the
two complementary services accident prevention and post-
accident investigation. Our WSN security architecture is
stimulated by the understanding that WSN roadside islands
will only be rolled-out and used when hardware costs are
close to the minimum. We provide a purely software based
security solution which does not rely on costly HW compo-
nents like road side units (RSU) or tamper resistant modules
on sensor nodes. We use existing components, but also de-
scribe protocols that may be of independent interest.
- Jens-Matthias Bohli, Jörn Müller-Quade, and Stefan Röhrich
"Bingo Voting: Secure and coercion-free voting using a trusted random number generator"
E-Voting and Identity, VOTE-ID 2007, Lecture Notes in Computer Science, vol. 4896, pp. 111-124, Springer, 2007
[Abstract]
It is debatable if current direct-recording electronic votingmachines
can sufficiently be trusted for a use in elections. Reports about malfunctions
and possible ways ofmanipulation abound. Voting schemes have
to fulfill seemingly contradictory requirements: On one hand the election
process should be verifiable to prevent electoral fraud and on the other
hand each vote should be deniable to avoid coercion and vote buying.
This work presents a new verifiable and coercion-free voting scheme
Bingo Voting, which is based on a trusted random number generator. As
a motivation for the new scheme two coercion/vote buying attacks on
voting schemes are presented which show that it can be dangerous to let
the voter contribute randomness to the voting scheme.
A proof-of-concept implementation of the scheme shows the practicality
of the scheme: all costly computations can be moved to a non time
critical pre-voting phase.
- Jens-Matthias Bohli, Jörn Müller-Quade, and Stefan Röhrich
"Long-term Secure Key Establishment"
Long-Term and Dynamical Aspects of Information Security: Emerging Trends in Information and Communication Security,
Nova Science Publishers, ISBN 1-60021-912-8, 2007
[Abstract]
In this paper we present a long-term secure key establishment protocol. Long-term
security means resistance against attacks even if later, after completion of the protocol,
some security assumptions become invalid. This makes the attacker more powerful,
e.g. able to solve a formerly hard problem. In this setting we assume the hardness
of the Diffie-Hellman problem during the protocol run, but later the attacker is able to
solve the discrete logarithm problem which, e.g., is possible if quantum computers can
be built. We achieve the security through combining the computationalDiffie-Hellman
key exchange with a classic Needham-Schroeder like protocol which uses symmetric
encryption and a key distribution server. There are no known fundamental quantumattacks
against good symmetric encryption schemes, which gives us long-term security.
Through combination with the Diffie-Hellmann key exchange we achieve protection
against a corrupted server as long as the Diffie-Hellman assumption holds and it allows
us to give an efficient protocol with three rounds and five messages.
- Jens-Matthias Bohli, María Isabel González Vasco, and Rainer Steinwandt
"Secure Group Key Establishment Revisited"
International Journal of Information Security,
vol. 6, no. 4, pp. 243-254, 2007
[Abstract]
We examine the popular proof models for group key establishment of
Bresson et al. and point out missing security
properties addressing malicious protocol participants.
We show that established group key establishment
schemes from CRYPTO 2003 and ASIACRYPT 2004 do
not fully meet these new requirements. Next to giving a formal
definition of these extended security properties, we prove a
variant of the explored proposal from ASIACRYPT 2004
secure in this stricter sense. Our proof builds on the Computational Diffie Hellman (CDH) assumption and the random oracle model.
- Michel Abdalla, Jens-Matthias Bohli, María Isabel González
Vasco and Rainer Steinwandt
"(Password) Authenticated Key Establishment: From 2-Party to Group"
Theory of Cryptography Conference -- TCC 2007,
Lecture Notes in Computer Science, vol. 4392, pp. 499-514, Springer, 2007
- Jens-Matthias Bohli, Benjamin Glas and Rainer Steinwandt
"Towards Provably Secure Group Key Agreement Building on Group Theory"
Progress in Cryptology -- VIETCRYPT 2006,
Lecture Notes in Computer Science, vol. 4341, pp. 322-336, Springer, 2006
- Jens-Matthias Bohli and Rainer Steinwandt
"Deniable Group Key Agreement"
Progress in Cryptology -- VIETCRYPT 2006,
Lecture Notes in Computer Science, vol. 4341, pp. 298-311, Springer, 2006
[Abstract]
Especially for key establishment protocols to be used in internet
applications, the (privacy) concern of deniability
arises: Can a protocol transcript be used---possibly by a
participant---to prove the involvement of another party in the protocol?
For two party key establishment protocols, a common technique for achieving
deniability is the replacement of signature-based message
authentication with authentication based on symmetric keys.
We explore the question of deniability in the context of group key establishment: Taking into account malicious insiders, using a
common symmetric key for authentication is critical, and the question of how to achieve deniability arises.
Building on a model of Bresson et al., we offer a formalization of deniability and present a group key agreement offering
provable security in the usual sense, deniability, and security guarantees against malicious insiders. Our approach for achieving deniability through
a suitably distributed Schnorr-signature might also be of independent interest.
- Jens-Matthias Bohli, Benjamin Glas and Rainer Steinwandt
"Algebraic Cryptosystems and Side Channel Attacks: Braid Groups and DPA"
accepted for publication in Congressus Numerantium
- Jens-Matthias Bohli, María Isabel González Vasco and Rainer Steinwandt
"A Subliminal-free Variant of ECDSA"
Information Hiding -- IH2006,
Lecture Notes in Computer Science, vol. 4437, pp. 375-387, Springer, 2007
- Jens-Matthias Bohli
"A Framework for Robust Group Key Agreement"
ACIS'06 in Computational Science and Its Applications -- ICCSA 2006 (3),
Lecture Notes in Computer Science, vol. 3982, pp. 355-364, Springer, 2006
- Jens-Matthias Bohli, Stefan Röhrich and Rainer Steinwandt
"Key substitution attacks revisited: Taking into account malicious signers"
International Journal of Information Security,
vol. 5, no. 1, pp. 30-36, 2006
- Jens-Matthias Bohli, Jörn Müller-Quade and Stefan Röhrich
"Fairness and Correctness in Case of a Premature Abort"
Progress in Cryptology -- INDOCRYPT 2005,
Lecture Notes in Computer Science, vol. 3797, pp. 322-331, Springer, 2005
- Jens-Matthias Bohli, María Isabel González Vasco and Rainer Steinwandt
"Burmester-Desmedt Tree-Based Key Transport Revisited: Provable Security."
Cryptology ePrint Archive, Report 2005/360
- Jens-Matthias Bohli, Jörn Müller-Quade and Stefan Röhrich
"On Group Key Agreement with Cheater Identification"
Western European Workshop on Research in Cryptology 2005, Leuven
- Jens-Matthias Bohli, María Isabel González Vasco, Consuelo Martínez and Rainer
Steinwandt
"Weak Keys in MST1"
Designs, Codes and Cryptography,
vol. 37, no. 3, pp. 509-524, 2005.
- Jens-Matthias Bohli and Rainer Steinwandt
"On Subliminal Channels in Deterministic Signature Schemes"
Information Security and Cryptology - ICISC 2004,
Lecture Notes in Computer Science, vol. 3506, pp. 182-194, Springer, 2005.
- Jens-Matthias Bohli
"Algorithmen für iterative Entscheidungen in der Signalverarbeitung"
Diplomarbeit, Universität Karlsruhe, 2003
- Jens-Matthias Bohli
"Schwache Schlüssel des Public-Key-Systems $MST_1$"
Studienarbeit, Universität Karlsruhe, 2001
