In a recent paper, an improvement of quantum sealed-bid auction protocol is proposed by introducing hash function. However, in this comment, it is shown that the improvement brings in other problems which would not complete the task of a sealed-bid auction fairly.
In this paper, the cryptanalysis about the quantum sealed-bid auction, whose feature is that by introducing a postconfirmation mechanism the malicious bidders cannot collude with auctioneers, is given. We found that a malicious bidder can obtain the other bidders' bids with a probability of 0.854. Moreover, there will be a higher probability if some bidders collude to attack the other bidders' bids. To prevent such attacks, we propose an effective improvement by means of the hash function.