Timothé Bramas

Bit commitment is a fundamental primitive of secure two-party computation. While unconditional quantum security remains impossible without additional assumptions, the noisy-storage model offers a path forward by assuming limited adversarial quantum memory. Existing protocols in the noisy-storage model have addressed realistic photon sources. However, Measurement-Device-Independence (MDI), a powerful technique developed primarily for Quantum Key Distribution to eliminate vulnerabilities from untrusted measurement devices, has not yet been applied to bit commitment. In this work, we introduce MDI protocols for Randomised String Commitment (RSC) in the noisy-storage model and analyse their security with both ideal single-photon sources and practical photon sources. Our first protocol handles multiphoton emissions from weak coherent pulse sources using decoy-state techniques. We demonstrate that positive secure committed string rates are achievable in the asymptotic limit despite source imperfections. Our second protocol takes a fundamentally different approach, drawing inspiration from Twin-Field Quantum Key Distribution: both parties send phase-modulated coherent pulses to a central station performing single-photon interference. Showing that this protocol achieves positive committed string rates is part of ongoing work. Our work brings MDI bit commitment closer to experimental realisation and opens a new design direction by leveraging the toolbox developed for twin-field protocols.