  Recently, a quantum multi-party summation protocol based on the quantum
Fourier transform has been proposed [Quantum Inf Process 17: 129, 2018]. The
protocol claims to be secure against both outside and participant attacks.
However, a closer look reveals that the player in charge of generating the
required multi-partite entangled states can launch two kinds of attacks to
learn about other parties' private integer strings without being caught. In
this paper, we present these attacks, and propose countermeasures to make the
protocol secure again. The improved protocol not only can resist these attacks
but also remove the need for the quantum Fourier transform and encoding quantum
operations by participants.
