Cryptographic techniques are used to secure confidential data from unauthorized access but these techniques are
very sensitive to noise. A single bit change in encrypted data can have catastrophic impact over the decrypted
data. This paper addresses the problem of removing bit error in visual data which are encrypted using AES
algorithm in the CBC mode. In order to remove the noise, a method is proposed which is based on the statistical
analysis of each block during the decryption. The proposed method exploits local statistics of the visual data
and confusion/diffusion properties of the encryption algorithm to remove the errors. Experimental results show
that the proposed method can be used at the receiving end for the possible solution for noise removing in visual
data in encrypted domain.
Multiplicative homomorphic properties of a cryptosystem can be used in various applications requiring security,
protection and authentication e.g. digital fingerprinting, electronic voting, on line betting etc. Secret sharing
between two or more parties exploiting multiplicative homomorphic property of RSA results into erroneous blocks
while extracting the message. The generation of these erroneous blocks limits the capabilities of homomorphic
properties of RSA to be used in its full extend. This paper provides three different approaches as solutions to
the problem of erroneous blocks in image. These solutions are: mean value approach, shortest distance approach
and image preprocessing approach. It has been observed that shortest distance approach results into good
PSNR but it is computationally expensive. The best approach with high PSNR is image preprocessing approach
before sharing process, which results into no erroneous blocks in the extracted image, thus no extra extraction
techniques are required.
In this paper we present a new approach for sharing a secret image between l users exploiting additive homomorphic
property of Paillier algorithm. With a traditional approach, when a dealer wants to share an image between
l players, the secret image must be sequentially encrypted l + 1 times using l + 1 keys (secret or public keys).
When the dealer and the l players want to extract the secret image, they must decrypt sequentially, keeping the
same order of the encryption step, by using l + 1 keys (secret or private). With the proposed approach, during
the encryption step, each player encrypts his own secret image using the same public key given by the dealer,
the dealer encrypts the secret image to be shared with the same key and then the l secret encrypted images plus
the encrypted image to be shared are multiplied between them to get a scrambled image. After this step, the
dealer can securely use the private key to decrypt this scrambled image to get a new scrambled image which
corresponds to the addition of the l + 1 original images because of the additive homomorphic property of Paillier
algorithm. When the l players want to extract the secret image, they do not need the dealer and to use keys.
Indeed, with our approach, to extract the secret image, the l players need only to subtract their own secret image
from the scrambled image. In this paper we illustrate our approach with an example of a captain who wants to
share a secret treasure map between l pirates. Experimental results and security analysis show the effectiveness
of the proposed scheme.