Quantum Computation and Information Seminar 

25/07/2014, 16:15 — 17:15 — Room P3.10, Mathematics Building
Ricardo Loura, SQIG - IT

Noise Analysis of a Two-state Quantum Bit Commitment Protocol

Commitment schemes are fundamental primitives in cryptography. In particular, a Bit Commitment (BC) scheme allows one user, Alice, to choose a bit value $b=\{0,1\}$, and upon request prove to a second user, Bob, that the value she chose was indeed b. The protocol is said to be secure if Alice is unable to change her mind once the choice is made, and Bob is unable to discover Alice’s choice until she willingly presents her proof. Unfortunately, there are no unconditionally secure BC protocols, meaning that the security of BC protocols relies on some assumptions. In the classical world, these assumptions are of computational nature. In this work, we present a BC protocol which makes use of quantum mechanical phenomena, and whose security is based on technological limitations rather than computational hardness. Furthermore, we carefully analyse the effects of noise throughout the entirety of the protocol, and prove that, in a sense, it is always advantageous for a cheating Alice to introduce extra noise prior to her measurements.