A Research Of Power Analysis Attacks Method And Countermeasures On Advanced Encryption Standard

The application of smart card is increasing in such fields like transportation, electronic money, ID card, etc. Major advantage of smart card is that internal data like secret key can be used for internal processing and only the result is open to the public access. However, the internal data kept inside smart card can be found out using side channel attack. When cryptographic processing is occurred using input message and secret key, side channel signals like power consumption or electromagnetic radiation may be leaked and used to find out the secret key.Power analysis is a kind of side channel attacks that makes use of power consumption information. It is a key technique in encryption field and this technique is based on its cross-correlation between the operation instruction, data in cryption system and the power consumption. The attacker can obtain the relevant power curves easily, whether the cryption system is realized by hardware or software. Power analysis technique is a serious menace for cryption system. It is necessary to study that how to break the encryption system using power analysis technique and designing advanced encryption algorithms that can prevent power analysis.In this thesis, the methods and key techniques of power attacks against AES and mathematic analysis are studied. New countermeasure algorithms is provided. The main works are described as follows:Firstly, The fundamental principle of differential power analysis attacks(DPA) against Advanced Encryption Standard(AES) are described in detail. An improved model is proposed for DPA Based on the simulation of DPA power by Hamming Distance and the method of correlation factor. Based on this model, a principle to selecting D function is proposed and corresponding theory is demonstrated, experimental results of the simulation are presented and the "ghost peak" problem is explained. Secondly, a new method based on Walsh spectrum is proposed to reveal the key embedded in cryptographic. Furthermore, conclusion are drawn and proved that the vulnerability against power analysis caused by the highly nonlinear S-boxes. Experimental results indicate that the new method speeds up the revelation of key and yields higher precision.At last, the advanced MASK method against power analysis attacks is introduced. The advantage and disadvantage between the Boolean Masking Method and the Multiplicative Masking method are analysis. Based on the small size smart card using logic circuit, a modification of masking method that is resistant to HODPA and more efficient than previous methods is proposed.