Group-Oriented Encryption and Signature
Date Issued
2004
Date
2004
Author(s)
Wu, Ming-Luen
DOI
en-US
Abstract
Computer networks bring tremendous progress to the
information-based society. Companies, organizations, and
governments have been using computers and networks to process or transmit digital data. But this also results in many different types of security requirements for group-oriented cryptographic applications.
In this thesis we study existing cryptographic tools and then use them to design more complex cryptographic systems. Several fundamental cryptographic primitives are useful not only as stand-alone applications but also as building blocks in the designing of secure cryptographic objects. Using these building blocks, we develop new cryptographic applications, including a full public-key traitor-tracing scheme and a convertible group undeniable signature scheme.
A fully public-key traitor-tracing scheme is a public-key
traitor-tracing scheme that allows a subscriber to choose his or her own private decryption key without others learning the key. The distributor of the digital content uses the public data coming from all subscribers to compute a public encryption key. The paid contents are then transmitted to the subscribers, after being
encrypted with the public key. Each subscriber can decrypt the data using his or her own secret key. Even if a coalition of subscribers conspire to create a pirate decoder with a tamper-free decryption key, there is a tracing algorithm to trace them. A realization of the scheme is presented in this thesis. Our scheme is long-lived, which means that the subscribers' secret keys need
not be regenerated after the pirate key is detected or when
subscribers join or leave the system. Finally, our scheme
guarantees anonymity.
A group undeniable signature satisfies the following
requirements: (1) only group members can anonymously sign on behalf of the group; (2) a verifier must interact with the group manager to verify the signature; (3) the group manager can identify the signer of a valid signature. A convertible group undeniable signature scheme allows the group manager to turn select group undeniable signatures into universally verifiable group signatures. An efficient realization of the scheme is proposed in this thesis. Our scheme is unforgeable, exculpable, unlinkable, and coalition-resistant. The proposed scheme allows the group manager to delegate the ability to confirm and deny signatures to trusted parties. The sizes of the public key and signatures are independent of the group size.
Subjects
可轉換性
群體不可否認簽章
背叛者追蹤
group undeniable signature
traitor-tracing
convertibility
Type
thesis
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