LASIGE Talks are fortnightly/monthly events to publicize recently distinguished publications or ongoing cutting-edge work by researchers from the research centre, consolidating the scientific culture of the LASIGE community.

Speakers: João Ferreira (LASIGE) and Hasan Heydari (LASIGE)
Date: December 11, 2024, 11h45
Where: C6.3.27

Program:
11:45 João Ferreira
12:05 Hasan Heydari
12:25 Q&A + Lunch

Talk1: CRAFTING VIRTUAL REALITIES: DESIGNING A VR END-USER AUTHORING PLATFORM FOR PERSONALISED EXPOSURE THERAPY
Speaker: João Ferreira
Exposure therapy (ET) gradually introduces people to the objects, animals, or situations they fear to help them overcome the angst with that source of anxiety. VR(ET) enables exposure to various triggers in the safety of the
clinical or home environments. While prior work has explored how specific VR environments support therapy in contexts such as social anxiety or arachnophobia, therapy’s individualised nature is often overlooked. We used
an iterative participatory design approach to develop an authoring platform for therapists, enabling them to tailor VR environments during exposure by changing and parameterising elements and reapplying past scenes. We used this platform as a design probe in a study with ten therapists to elicit discussions about the design of VRET experiences and therapists’ authoring needs. Findings highlight the value of controlling the stimuli presented to patients and deviating from stereotypical scenarios, and the importance of further investigating the therapist’s virtual representation. João Ferreira’s research falls in the IHCI research line.

Talk2: FROM BIRTHDAY PARADOX TO BYZANTINE CONSENSUS-IMPROVING MESSAGE COMPLEXITY
IN BLOCKCHAINS
Speaker: Hasan Heydari
Byzantine consensus is a classical distributed computing problem in which a set of peers must agree on a single value among those they propose. In recent years, the rise of blockchains has made this problem extremely relevant, as these systems require mutually untrusted nodes to agree on a sequence of valid
transactions to be processed. Most protocols addressing this problem are deterministic, adopting a pessimistic approach where the adversary has control over the network, leading to a high number of messages being exchanged. The birthday paradox, a counterintuitive concept from combinatorics, demonstrates
that, in a group of just 23 people, there is a greater than 50% chance that two people share the same birthday.
However, to ensure two people have the same birthday deterministically, a group with 366 people is required due to the pigeonhole principle! In this talk, we will explore how the birthday paradox combined with cryptographic tools such as verifiable random functions, can be employed to design a novel consensus protocol in pragmatic settings where the adversary has less control over the network. This consensus protocol guarantees safety and liveness with high probability while achieving a message complexity of $O(n\sqrt{n})$ — an improvement of $\sqrt{n}$ over previous latency-optimal protocols. Hasan Heydari’s research falls in the CPS, DS2, ToC research lines.