SARG04 Protocol: PNS-Resistant Quantum Key Distribution

SARG04 is a variant of quantum key distribution built on the same four polarization states as BB84 — but it changes the sifting rule that turns raw photon measurements into a shared secret key. Rather than revealing which basis she used, Alice reveals a pair of non-orthogonal states that includes the one she actually sent, and Bob can only extract a bit when his own measurement rules out one member of that pair by elimination. This simulator streams polarized photons across a real optical channel in 3D, applies the exact SARG04 sifting logic every round, and tracks the resulting key rate and error rate live — including what happens the moment an intercept-resend eavesdropper joins the line, which is precisely the attack this protocol was designed to make costlier to hide.