The document discusses an enhanced cloud storage solution that ensures data reliability and confidentiality while allowing efficient data forwarding without retrieval. It introduces an all-or-nothing-transform-based encryption and a variant of ElGamal proxy re-encryption, which improves efficiency by only requiring updates to partial data blocks. The scheme ensures that the original data owner cannot decrypt or forward the re-encrypted data after a complete forwarding, a feature called 'original inaccessibility'.

1. Reliable and confidential cloud storage with efficient data forwarding
functionality
Abstract:
Cloud computing is a promising computing paradigm which has drawn extensive
attention. Serious concerns over the reliability and confidentiality of the
outsourced data are arising. Traditional encryption methods can, guarantee data
confidentiality, however, it also limits the cloud's functionality as few operations
are supported over encrypted data. In this study, the authors construct an
enhanced cloudthat not only provides secure and robust data storage, but also
supports the functionality that the cipher data can be forwarded without being
retrieved back. Specifically, they design an all-or-nothing-transform-based
encryption and a variant of ElGamal-based proxy re-encryption algorithms,
blending them with Reed-Solomon code, the authors' scheme is quite more
efficient compared with previous studies because it only needs to update partial
data blocks instead of the whole file for data forwarding. Besides, the authors'
scheme also satisfies another practical property that the original data owner can
no longer decrypt or forward the re-encrypted data to others after a complete
forwarding instance, which is termed to be `original inaccessibility' in this study.
Analysis shows that the authors' scheme is secure and satisfactory. Finally, the
authors theoretically and experimentally evaluate its performance and the results
indicate that their scheme is efficient during file dispersal, forward and retrieval.