  Recently, Xie et al. (IEEE Transactions on Information Forensics and
Security, vol. 16, pp. 3068-3081, 2021) proposed a privacy-preserving Online
Ride-Hailing (ORH) protocol that does not make use of a trusted third-party
server. The primary goal of such privacy-preserving ORH protocols is to ensure
the privacy of riders' and drivers' location data w.r.t. the ORH Service
Provider (SP). In this note, we demonstrate a passive attack by the SP in the
protocol of Xie et al. that enables it to completely recover the location of
the rider as well as that of the responding drivers in each and every ride
request query.
