Finding Collisions in a Quantum World: Quantum Black-Box Separation of Collision-Resistance and One-Wayness

Since the celebrated work of Impagliazzo and Rudich (STOC 1989), a number of black-box impossibility results have been established. However, these works only ruled out classical black-box reductions among cryptographic primitives. Therefore it may be possible to overcome these impossibility results by using quantum reductions. To exclude such a possibility, we have to extend these impossibility results to the quantum setting. In this paper, we study black-box impossibility in the quantum setting. We first formalize a quantum counterpart of fully-black-box reduction following the formalization by Reingold, Trevisan and Vadhan (TCC 2004). Then we prove that there is no quantum fully-black-box reduction from collision-resistant hash functions to one-way permutations (or even trapdoor permutations). We take both of classical and quantum implementations of primitives into account. This is an extension to the quantum setting of the work of Simon (Eurocrypt 1998) who showed a similar result in the classical setting

Long-range charge transport in single G-quadruplex DNA molecules

DNA and DNA-based polymers are of interest in molecular electronics because of their versatile and programmable structures. However, transport measurements have produced a range of seemingly contradictory results due to differences in the measured molecules and experimental set-ups, and transporting significant current through individual DNA-based molecules remains a considerable challenge. Here, we report reproducible charge transport in guanine-quadruplex (G4) DNA molecules adsorbed on a mica substrate. Currents ranging from tens of picoamperes to more than 100 pA were measured in the G4-DNA over distances ranging from tens of nanometres to more than 100 nm. Our experimental results, combined with theoretical modelling, suggest that transport occurs via a thermally activated long-range hopping between multi-tetrad segments of DNA. These results could re-ignite interest in DNA-based wires and devices, and in the use of such systems in the development of programmable circuits