  The evolution of Quantum Key Distribution (QKD) relies on innovative methods
to enhance its security and efficiency. Unextendible Product Bases (UPBs) hold
promise in quantum cryptography due to their inherent indistinguishability, yet
they are underutilized in QKD protocols. This work introduces a protocol
utilizing UPBs to establish quantum keys between distant parties. Specifically,
we propose a protocol utilizing a $3\times 3$ tile UPB, where Alice
sequentially transmits subsystem states to Bob through quantum channels. The
protocol's security is underpinned by the no-cloning theorem, prohibiting the
cloning of orthogonal states. We analyze potential attacks, including
intercept-resend and detector blinding attacks when quantum channels are
noiseless, and discuss the challenges posed by the indistinguishability of our
protocol for eavesdroppers, thereby enhancing QKD security.
