  Quantum algorithm is a key tool for cryptanalysis. At present, people are
committed to building powerful quantum algorithms and tapping the potential of
quantum algorithms, so as to further analyze the security of cryptographic
algorithms under quantum computing. Recombining classical quantum algorithms is
one of the current ideas to construct quantum algorithms. However, they cannot
be easily combined, the feasibility of quantum algorithms needs further
analysis in quantum environment. This paper reanalyzes the existing combined
algorithm Grover-meets-Simon algorithm in terms of the principle of deferred
measurement. First of all, due to the collapse problem caused by the
measurement, we negate the measurement process of Simon's algorithm during the
process of the Grover-meets-Simon algorithm. Second, since the output of the
unmeasured Simon algorithm is quantum linear systems of equations, we discuss
the solution of quantum linear systems of equations and find it feasible to
consider the deferred measurement of the parallel Simon algorithm alone.
Finally, since the Grover-meets-Simon algorithm involves an iterative problem,
we reconsider the feasibility of the algorithm when placing multiple
measurements at the end. According to the maximum probability of success and
query times, we get that the Grover-meets-Simon algorithm is not an effective
attack algorithm when putting the measurement process of the Simon algorithm in
the iterative process at the end of Grover-meets-Simon algorithm.
