Restricted universal designated verifier signature
Similar to hand-written signatures, digital signatures are designed to provide authenticity, integrity and non-repudiation. In the arena of ubiquitous computing, the ability of convincing any third party should be restricted. In a service such as an Internet trial-browsing service, a user is allowed to access the service of t times without any charge, but will be charged on the t+1 count of access. In this paper, we introduce the notion of restricted universal designated verifier signature. In this notion, a signature holder can convince up to t verifiers, and the convincing statement is designated to these verifiers. However, when the signature holder uses the signature for t+1 times, then the signature will become publicly available. We note that this type of signature schemes has many applications in practice.