Biblio

In this paper, we present the enhancement of a lightweight key-policy attribute-based encryption (KP-ABE) scheme designed for the Internet of Things (IoT). The KP-ABE scheme was claimed to achieve ciphertext indistinguishability under chosen-plaintext attack in the selective-set model but we show that the KP-ABE scheme is insecure even in the weaker security notion, namely, one-way encryption under the same attack and model. In particular, we show that an attacker can decrypt a ciphertext which does not satisfy the policy imposed on his decryption key. Subsequently, we propose an efficient fix to the KP-ABE scheme as well as extending it to be a hierarchical KP-ABE (H-KP-ABE) scheme that can support role delegation in IoT applications. An example of applying our H-KP-ABE on an IoT-connected healthcare system is given to highlight the benefit of the delegation feature. Lastly, using the NIST curves secp192k1 and secp256k1, we benchmark the fixed (hierarchical) KP-ABE scheme on an Android phone and the result shows that the scheme is still the fastest in the literature.

Steganography is a method of hiding information, whereas the goal of cryptography is to make data unreadable. Both of these methodologies have their own advantages and disadvantages. Encrypted messages are easily detectable. If someone is spying on communication channel for encrypted message, he/she can easily identify the encrypted messages. Encryption may draw unnecessary attention to the transferred messages. This may lead to cryptanalysis of the encrypted message if the spy tries to know the message. If the encryption technique is not strong enough, the message may be deciphered. In contrast, Steganography tries to hide the data from third party by smartly embedding the data to some other file which is not at all related to the message. Here care is to be taken to minimize the modification of the container file in the process of embedding data. But the disadvantage of steganography is that it is not as secure as cryptography. In the present method the authors have introduced three-step security. Firstly the secret message is encrypted using bit level columnar transposition method introduced by Nath et al and after that the encrypted message is embedded in some image file along with its size. Finally the modified image is encoded into a QR Code TM. The entire method has also been implemented for the Android mobile environment. This method may be used to transfer confidential message through Android mobile phone.