  Recently an attack strategy was proposed by Chau [H. F. Chau,
quant-ph/0602099 v3], which was claimed to be able to break all quantum string
seal protocols, including the one proposed by He [G. P. He, Int. J. Quant.
Inform. 4, 677 (2006)]. Here it will be shown that the information obtained in
He's protocol by the attack is trivial. Thus Chau's conclusion that all quantum
string seals are insecure is wrong. It will also be shown that some other
claims in Chau's paper are inaccurate either.
