Differential Fault Analysis Of Block Ciphers

Differential Fault Analysis (DFA) is a kind of attack which based on attacking implementation of algorithms by faults induced in hardwares. Since its emergence, DFA has been applied to several kinds of ciphers in our real world, containing public key ciphers and block ciphers. In this thesis, using byte-oriented random fault model, we mainly focus on application of DFA on three kinds of block cipher Serpent , KeeLoq and FOX.Serpent is a new block cipher as a candidate for the Advanced Encryption Standard. By using techniques of differential cryptanalysis and the specialty of the diffusion layer and the key schedule, we present a practical fault analysis attacks on Serpent. It is shown by experiments that the 128 bit master key can be obtained through 20 faulty ciphertexts on average. The results imply that Serpent is not immune to differential fault analysis.KeeLoq is a block cipher with a 32-bit block size and a 64-bit key. It is widely used in wireless devices that unlock the doors and alarms in cars manufactured. In this paper, based on the differential property of the non-linear function NLF, we present a practical differential fault analysis attacks on KeeLoq. Theory and experiments show that we can recover 1 bit key through 0.71 faulty ciphertexts on average.FOX is a family of symmetric block ciphers that helps to secure digital media, communications, and storage. In this paper, we present an improved fault attack on FOX64. Our improved method can deduce any round subkey through 4.25 faults on average. Compared with the previous fault attack, which recovers the last round sub-key through 11.45 faults on average, the number of faults in our improved attack is significantly reduced. Further, the technique of the proposed attack in this paper can also be easily extended to other series of FOX.