Abstract
In this paper we emphasize the importance of unique certified one-time key pairs in Buyer-Seller Watermarking (BSW) protocols. We distinguish between reactive unbinding attacks, in which the seller reacts to illicit file sharing by fabricating further evidence of such activity, and pre-emptive unbinding attacks, in which the seller gains an advantage by taking action that pre-empts the file being shared. We demonstrate the importance of certified one-time key pairs in the BSW protocol by Lei et al., for protecting against pre-emptive unbinding attacks, and subsequently reveal a new attack on a recently published BSW protocol due to its omission of unique key pairs.