||An efficient and fault-tolerant cloud storage scheme for file owners is presented in this paper.|
A large file is first divided into secrets, and each secret is then divided
into shares by using a (k, l, L, n)-threshold secret sharing scheme.
These shares are finally uploaded into n-l cloud storage servers.
To retrieve the file, any k shares of each secret are first retrieved
from some of the servers.
The value of each secret can then be computed from these k shares, and
the original files can then be assembled from these secrets.
The scheme achieves the following security for the file owners:
(1) Secrecy: at least k shares are obtained, the contents of the file
cannot be reconstructed, including the cloud storage owner.
(2) Fault-tolerant: Only need k shares to reconstruct the file.
(3) Can be used to delete a file permanently: by letting k=n and store one
share by the file owner.
If the share stored by the file owner is deleted, the file can no longer
be reconstructed any more.
The proposed scheme adopted the Satoshi et al.'s secret sharing scheme and J. Kurihara et al's ramp secret sharing scheme to reduce
the total storage required.
It uses J. Kurihara et al's ramp secret sharing scheme, in which only XOR operations are
needed to reduce the computational cost.
The improvement is significant when n is small and the secret size is
large, the efficiency of the scheme.
Therefore, the proposed protocol is practical in cloud storage.