  It is called blind quantum computation(BQC) that a client who has limited
quantum technologies can delegate her quantum computing to a server who has
fully-advanced quantum computers. But the privacy of the client's quantum
inputs, algorithms and outputs is still a challenge. To realize a secure BQC,
we mainly study how to hide quantum fourier transform (QFT) performed on Bell
states. In this paper, three cases are considered as follows. For the first
case, we design primary BQC protocols of QFT performed on qubits 12 of
belonging to $\{|\phi^\pm\rangle_{12},$ $|\psi^\pm\rangle_{12}\}$ with relevant
circuits. To strengthen security, we construct enhanced BQC protocols of QFT
performed on qubits 13 of any two Bell states
$|\xi\rangle_{12}\otimes|\theta\rangle_{34}$ with relevant quantum circuits.
Featured the property of stronger security, we give generalized BQC protocols
of QFT performed on qubits 13 and 24 of any two Bell states with relevant
quantum circuits respectively. At last, we analyze and prove the blindness and
correctness.
