ABSTRACT
With data storage and sharing services in
the cloud, users can easily modify and share data as a group. To ensure share data
integrity can be verified publicly, users in the group need to compute
signatures on all the blocks in shared data. Different blocks in shared data
are generally signed by different users due to data modifications performed by
different users. For security reasons, once a user is revoked from the group,
the blocks which were previously signed by this revoked user must be re-signed
by an existing user. The straightforward method, which allows an existing user
to download the corresponding part of shared data and re-sign it during user revocation,
is inefficient due to the large size of shared data in the cloud. In this paper,
we propose a novel public auditing mechanism
For
the integrity of shared data with efficient user revocation in mind. By
utilizing the idea of proxy re-signatures, we allow the cloud tore-sign blocks
on behalf of existing users during user revocation, so that existing users do
not need to download and re-sign blocks by themselves. In addition, a public
verifier is always able to audit the integrity of shared data without
retrieving the entire data from the
Cloud, even
if some part of shared data has been re-signed by the cloud. Moreover, our
mechanism is able to support batch auditing by verifying multiple auditing
tasks simultaneously. Experimental results show that our mechanism can
significantly improve the efficiency of user revocation.
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