Jintai Ding, from the Department of Mathematics of the University of Cincinnati
Date & time: Friday, January 18th, 16:00h - 17:00
Location: Instituto Superior Técnico, Lisbon, Room P3.10, Mathematics Building
Blockchain technology is now going through explosive development with the aim to build a new generation of revolutionary financial technology. The most successful example is new digital currency bitcoin. The fundamental building block in blockchain technology is actually cryptographic algorithms, which is why bitcoin is actually called a cryptocurrency. The main cryptographic algorithms used in blockchain technology are hash functions and elliptic curve digital signatures. As we all know, quantum computers are not such a significant threat to the security of Hash functions but it can be fatal to the elliptic curve digital signatures. In this presentation, we will first show how the quantum computers can threat the security of blockchain technology, in particular, why the existing blockchain technology used in bitcoins can not fundamentally avoid such a practical attack. Then we will explain the challenges we will face if if we just plug in existing post-quantum cryptographic solutions as a drop-in to replace the existing elliptic curve signatures, in particular, the key size problem and a few others. In the end, we will present some of the new solutions we have been developing to deal with these fundamental problems including a new type of proof of work algorithms, which, we believe, provide very viable solutions for the future long term secure blockchain technology.
Gonçalo Quinta and Rui André, from Instituto Superior Técnico
Date & time: Wednesday, December 5th, 16:00h
Location: Instituto Superior Técnico, Lisbon, Seminar room (2.8.3), Physics Building
We present a classification scheme for quantum entanglement based on topological links. This is done by identifying a nonrigid ring to a particle, attributing the act of cutting and removing a ring to the operation of tracing out the particle, and associating linked rings to entangled particles. This analogy naturally leads us to a classification of multipartite quantum entanglement based on all possible distinct links for any given number of rings. We demonstrate the use of this new classification scheme for three and four qubits and its potential in the context of qubit networks. More Information..