Christoph Ludwig

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We propose a practical sampling reduction algorithm for lattice bases based on work by Schnorr [1] as well as two even more effective generalizations. We report the empirical behaviour of these algorithms. We describe how Sampling Reduction allows to stage lattice attacks against the NTRU cryptosystem with smaller BKZ parameters than before and conclude(More)
We report experiments on the security of the GGH-like cryptosystem proposed by Micciancio. Based on these experiments, we conclude that the system can be securely used only in lattice dimensions ≥ 782. Further experiments on the efficiency of the system show that it requires key sizes of 1MByte and more and that the key generation as well as the decryption(More)
We propose a new lattice reduction method. Our algorithm approximates shortest lattice vectors up to a factor ≤ (k/6) and makes use of Grover’s quantum search algorithm. The proposed method has the expected running time O(n(k/6)A+nA). That is about the square root of the running time O(n(k/6)A+nA) of Schnorr’s recent random sampling reduction which in turn(More)
Digital signatures have become a key technology for making the Internet and other IT infrastructures secure. But in 1994 Peter Shor showed that quantum computers can break all digital signature schemes that are used today and in 2001 Chuang and his coworkers implemented Shor’s algorithm for the first time on a 7-qubit NMR quantum computer. This paper(More)
We describe the Distributed Object-Oriented Threads System (DOTS), a programming environment designed to support object-oriented fork/join parallel programming in a heterogeneous distributed environment. A mixed network of Windows NT PC’s and UNIX workstations is transformed by DOTS into a homogeneous pool of anonymous compute servers forming together a(More)
TextGrid is a new Grid project in the framework of the German D-Grid initiative, with the aim to deploy Grid technologies for humanities scholars working on historical (German) texts. Its two roots, humanities computing and eScience (Grid computing used by research together with modern communication technologies), are the basis for TextGrid to provide(More)
The last few years have seen a massive push towards collaborative working methods in the humanities. Many large and small eHumanities Digital Ecosystems (DEs) have sprung into existence. The big challenge ahead is now to see how these subsystems can begin to merge into one larger eHumanities DE while still maintaining their individual characters and(More)
The chirp of single-cycle microwave fields after interaction with pairs of parallel diffraction gratings is measured in a phase-sensitive terahertz spectrometer. Novel transmission grating pairs recently proposed by Tournois, which combine diffraction and refraction effects, yield an almost linear group delay over a bandwidth that exceeds that of(More)
Philological research is very much concerned with the idea of data provenance. However, existing provenance models in eResearch and eScience for data and workflow are ill-applicable to the specific challenges of philological research in the digital age. In philology, provenance data must be collected not only for the complete research objects, but also for(More)