Abstract-For the purpose of deterring unauthorized duplication and distribution of multimedia contents, a seller may insert a unique digital watermark into each copy of the multimedia contents to be sold. When an illegal replica is found in the market sometime later, the seller can determine the responsible distributor by examining the watermark embedded. However, the accusation against the charged distributor, who was the buyer in some earlier transaction, is objectionable because the seller also has access to the watermarked copies and, hence, is able to release such a replica on her own. In this paper, a watermarking protocol is proposed to avoid such difficulties, known as the customer's right problem, in the phase of arbitration. The proposed watermarking protocol also provides a fix to Memon and Wong's scheme by solving the unbinding problem. In addition, the buyer is no longer required to contact the watermark certification authority during transactions, and the anonymity of the buyer can be retained through a trusted third party. The result is an efficient and anonymous buyer-seller watermarking protocol.

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In the schemes designed for ubiquitous computing remote access to private dato is generally achieved by requiring users to deposit the data on certoin. always-on-line servers in the network infrastructure. However. when the data to be accessed remotely is somewhat sensitive, as implied by many opplications of personal computing, users may prefer to warehouse the data in their residences rather than in somepublicplaces. In this paper, a navel scheme is proposed to realize personal computing ubiquitously by satisfving such demand The proposed scheme employs home-automation techniques to grant properly authenticated users remote access to the dnta stored somewhere offthe i@astructure (e.g., their personal workstations) while avoiding the expense of deploying high-avoilability servers at home. It also provides three kin& of authentication mechanisms and hence allows users to choose among different levels of the tradeoff between security and ubiquity, providing a complete solution for ubiquitous personal computing.

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