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See detailA Decoder for a Symbol-Constrained Code (preliminary version)
Franck, Christian UL

E-print/Working paper (2017)

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See detailEfficient Implementation of Pedersen Commitments Using Twisted Edwards Curves
Franck, Christian UL; Groszschädl, Johann UL

in Mobile, Secure, and Programmable Networking - Third International Conference, {MSPN} 2017, Paris, France, June 29-30, 2017, Revised Selected Papers (2017)

Cryptographic commitment schemes are used in many contexts, whereby the size of the secret data and the security requirements depend on the target application. Using a software library that has been ... [more ▼]

Cryptographic commitment schemes are used in many contexts, whereby the size of the secret data and the security requirements depend on the target application. Using a software library that has been designed for other purposes (e.g., key-exchange or digital signatures) to compute commitments can be complicated or inefficient. We present in this paper a flexible implementation of Pedersen commitments based on elliptic curves in twisted Edwards form. The implementation supports a set of five curves of varying cryptographic strength, which are defined over 127, 159, 191, 223, and 255-bit pseudo-Mersenne prime fields. One can dynamically (i.e., at runtime) choose one of the curves according to the required level of security, and it is also possible to adapt to the size of the data to be committed by varying the number of base points. The point arithmetic is performed with optimized formulas using extended coordinates and dynamically pre-computed tables are utilized to speed up the scalar multiplication. Our implementation is written in ANSI C (with optional x86 assembler optimizations for the field arithmetic) and was compiled and tested successfully with Visual C on Windows, gcc on Linux, and clang on macOS. We present detailed benchmarking results for the field and point arithmetic on all five curves. When using an Intel Core i7 processor clocked at 2.7 GHz as test platform, we can compute more than 38,000 commitments per second on a twisted Edwards curve over a 127-bit field. [less ▲]

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See detailAssessing Performance of Internet of Things-based Mobile Crowdsensing Systems for Sensing as a Service Applications in Smart Cities
Capponi, Andrea UL; Fiandrino, Claudio UL; Franck, Christian UL et al

in 8th IEEE International Conference on Cloud Computing Technology and Science (CloudCom) (2016, December)

The Internet of Things (IoT) paradigm makes the Internet more pervasive. IoT devices are objects equipped with computing, storage and sensing capabilities and they are interconnected with communication ... [more ▼]

The Internet of Things (IoT) paradigm makes the Internet more pervasive. IoT devices are objects equipped with computing, storage and sensing capabilities and they are interconnected with communication technologies. Smart cities exploit the most advanced information technologies to improve public services. For being effective, smart cities require a massive amount of data, typically gathered from sensors. The application of the IoT paradigm to smart cities is an excellent solution to build sustainable Information and Communication Technology (ICT) platforms and to produce a large amount of data following Sensing as a Service (S^2aaS) business models. Having citizens involved in the process through mobile crowdsensing (MCS) techniques unleashes potential benefits as MCS augments the capabilities of existing sensing platforms. To this date, it remains an open challenge to quantify the costs the users sustain to contribute data with IoT devices such as the energy from the batteries and the amount of data generated at city-level. In this paper, we analyze existing solutions, we provide guidelines to design a large-scale urban level simulator and we present preliminary results from a prototype. [less ▲]

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See detailUntraceable VoIP Communication based on DC-nets
Franck, Christian UL; Sorger, Ulrich UL

E-print/Working paper (2016)

Untraceable communication is about hiding the identity of the sender or the recipient of a message. Currently most systems used in practice (e.g., TOR) rely on the principle that a message is routed via ... [more ▼]

Untraceable communication is about hiding the identity of the sender or the recipient of a message. Currently most systems used in practice (e.g., TOR) rely on the principle that a message is routed via several relays to obfuscate its path through the network. However, as this increases the end-to-end latency it is not ideal for applications like Voice-over-IP (VoIP) communication, where participants will notice annoying delays if the data does not arrive fast enough. We propose an approach based on the paradigm of Dining Cryptographer networks (DC-nets) that can be used to realize untraceable communication within small groups. The main features of our approach are low latency and resilience to packet-loss and fault packets sent by malicious players. We consider the special case of VoIP communication and propose techniques for a P2P implementation. We expose existing problems and sketch possible future large-scale systems composed of multiple groups. [less ▲]

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See detailSome Properties of Homogenous Trellis-Constrained Codes
Franck, Christian UL; Sorger, Ulrich UL

Poster (2016)

We consider Homogenous Trellis-Constrained Codes (HTCC), a generalization of Turbo-codes where all bits are constrained. No efficient decoding algorithm is known for these codes, so our results are ... [more ▼]

We consider Homogenous Trellis-Constrained Codes (HTCC), a generalization of Turbo-codes where all bits are constrained. No efficient decoding algorithm is known for these codes, so our results are primarily of theoretical interest. We propose a technique to derive an upper bound for the maximum-likelihood (ML) decoding of BSC errors. Our tech- nique is based on the weight distributions of the constituent codes and it can also be used when a specific number of errors e is known. We observe that with an ML-decoder some HTCC codes exhibit an error correcting performance close to that of random codes. For those codes we also observe a significant performance gap between ML-decoding and practical decoding based on belief-propagation. [less ▲]

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See detailDining Cryptographers are Practical
Franck, Christian UL; van de Graaf, Jeroen

E-print/Working paper (2015)

The dining cryptographers protocol provides information-theoretically secure sender and recipient untraceability. However, the protocol is considered to be impractical because a malicious participant may ... [more ▼]

The dining cryptographers protocol provides information-theoretically secure sender and recipient untraceability. However, the protocol is considered to be impractical because a malicious participant may disrupt the communication. We propose an implementation which provides information-theoretical security for senders and recipients, and in which a disruptor with limited computational capabilities can easily be detected. [less ▲]

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See detailDining Cryptographers with 0.924 Verifiable Collision Resolution
Franck, Christian UL

in Annales Universitatis Mariae Curie-Skłodowska. Sectio AI, Informatica (2014), 14(1), 49-59

The dining cryptographers protocol implements a multiple access channel in which senders and recipients are anonymous. A problem is that a malicious participant can disrupt communication by deliberately ... [more ▼]

The dining cryptographers protocol implements a multiple access channel in which senders and recipients are anonymous. A problem is that a malicious participant can disrupt communication by deliberately creating collisions. We propose a computationally secure dining cryptographers protocol with collision resolution that achieves a maximum stable throughput of 0.924 messages per round and which allows to easily detect disruptors. [less ▲]

Detailed reference viewed: 40 (4 UL)
See detailOn Intersection Codes and Iterative Decoding
Franck, Christian UL

Doctoral thesis (2013)

Detailed reference viewed: 100 (22 UL)
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See detailA Lower Bound for the Minimum Distance of Intersection Codes
Franck, Christian UL; Sorger, Ulrich UL

in A Lower Bound for the Minimum Distance of Intersection Codes (2010)

Intersection codes are a superclass of Turbo- and LDPC codes. This class contains codes constructed by intersecting interleaved constituent codes. We propose a lower bound for the minimum distance of ... [more ▼]

Intersection codes are a superclass of Turbo- and LDPC codes. This class contains codes constructed by intersecting interleaved constituent codes. We propose a lower bound for the minimum distance of these codes. Using this bound, we compare intersection codes obtained from different constituent codes. [less ▲]

Detailed reference viewed: 60 (4 UL)