Power analysis attacks on an implementation of AES algorithm

Cryptographic Algorithms are widely used in order to ensure information security. AES (Advanced Encryption Standard) algorithm is one of the algorithms of symmetric block encryption that are used for this purpose.The Advanced Encryption Standard (AES) is a cryptographic algorithm that published by National Institute of Standards and Technology (NIST) to protect electronic data in November 2001. It is widely used in cryptographic systems as from the date it is approved. The AES algorithm is a symmetric block cipher that can encrypt (encipher) and decrypt (decipher)information.AES algorithm, since it is mathematically powerful, is resistant to classical cryptoanalysis. However, there exists another attack technique that doesn?t care mathematical structure of the algorithm. This technique is side-channel analysis attacks.Side-channel attacks are considered as a fundamental threat by those who study about cryptography thanks to the first article about timing analysis published in 1996. No physical intervention is carried out to the cryptographic system in those attacks. The attacker analyzes data produced by the system during its runtime. If those data informs about parameters ensuring the confidentiality of the system, this information is called Side-channel Information.Side-channel analysis attacks are classified with respect to the side channel information that they use. Those are power analysis attacks, timing analysis attacks, electromagnetic analysis attacks and acoustics analysis attacks. The most powerful among them is power analysis attacks. A portion of power analysis attacks analyzes the relationship between the power that the cryptographic system consumes and the process that it carries out. This attack technique is called Simple Power Analysis (DPA).In another power analysis attack; however, the relationship between the power that the cryptographic system consumes and the data it processes is analyzed. This attack technique is called Differential Power Analysis (DPA). Especially DPA technique is pretty widely used. DPA attacks also implemented on AES algorithm.Some methods are offered to protect AES algorithm application against DPA attacks. One of these methods is masking application. In application of masking, Random data is added to intermediate values produced by the algorithm. That way, the attacker cannot make a connection between the intermediate value that the system produces and the consumed power. One of these masking techniques is IAIK Masking that proposes by Oswald. IAIK Masking is widely used in AES applications. However, different attacking techniques are offered for masked cryptographic systems as well. Those attacks are applicable for different situations and systems. Moreover, efficiency of each attack varies for different situations. Within this thesis, those attack techniques will be practically applied for a IAIK Masked AES Algorithm that implemented on an FPGA system. Later on, efficiency of each attack technique will be analyzed using real outcomes and they will be compared to each other.Keywords: Side channel attacks, differantial power analysis, IAIK mask.