  Quantum Key Distribution (QKD) is a technique enabling provable secure
communication but faces challenges in device characterization, posing potential
security risks. Device-Independent (DI) QKD protocols overcome this issue by
making minimal device assumptions but are limited in distance because they
require high detection efficiencies, which refer to the ability of the
experimental setup to detect quantum states. It is thus desirable to find
quantum key distribution protocols that are based on realistic assumptions on
the devices as well as implementable over long distances. In this work, we
consider a one-sided DI QKD scheme with two measurements per party and show
that it is secure against coherent attacks up to detection efficiencies greater
than 50.1% specifically on the untrusted side. This is almost the theoretical
limit achievable for protocols with two untrusted measurements. Interestingly,
we also show that, by placing the source of states close to the untrusted side,
our protocol is secure over distances comparable to standard QKD protocols.
