Affiliation: Institute of Information Engineering, CAS
On the Correctness of An Approach Against Side-channel attacks
Side-channel attacks are a very powerful cryptanalytic technique. Li and Gu [ProvSec'07] proposed an approach against side-channel attacks, which states that a symmetric encryption scheme is IND-secure in side-channel model, if it is IND-secure in black-box model and there is no adversary who can recover the whole key of the scheme computationally in side-channel model, i.e. WKR-SCA ^ IND -> IND-SCA. Our researches show that it is not the case. We analyze notions of security against key recovery attacks and security against distinguishing attacks, and then construct a scheme which is WKR-SCA-secure and IND-secure, but not IND-SCA-secure in the same side-channel environment. Furthermore, even if the scheme is secure again partial key recovery attacks in side-channel model, this approach still does not hold true.
Cryptanalysis of the MEM Mode of Operation
The MEM mode is a nonce-based enciphering mode of operation proposed by Chakraborty and Sarkar, which was claimed to be secure against symmetric nonce respecting adversaries. We show that this is not correct by using two very simple attcks. One attack need one decryption and one decryption queries, and the other only need one encryption query.