| Summary: | 碩士 === 國立政治大學 === 資訊科學系 === 107 === Policy-controlled signature (PCS) was first introduced by Thorncharoensri \textit{et al}. at ICICS $2009$. It is a new type of digital signature in which a signer can sign the message with some policies, but only verifiers who have the correct policy credentials can verify the signature. In the pioneering paper, Thorncharoensri \textit{et al}. proposed a generic construction based on bilinear pairings and defined its security models. With the rapid development of quantum computers, it will be difficult to avoid the quantum attacks in the future. This work shows that the attribute-based encryption and signature scheme can construct the policy-controlled signature scheme. Therefore, assuming that, with this preparation, a lattice could withstand quantum attacks, this work adopts Bert's signature protocol and Rahman's encryption protocol to propose the first decentralized PCS based on the lattice. Specifically, it is a decentralized scheme in which any user can become an authority and then issue a signer key or policy credentials. This thesis makes two contributions. On the one hand, it introduces the first policy-controlled signature that is quantum resistant. On the other hand, this new scheme avoids the problem of fully trusting a single certificate authority.
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