Generalised impossible differentials of advanced encryption standard

A class of generalized four-round impossible differentials of advanced encryption standard (AES) was presented. AES is a 128 bit block cipher with a 128,192 or 256 bit secret key. A data block of the AES is expressed as an array of 4*4 bytes with byte indexing. It was shown that these are the best that can be constructed with the miss-in-the- middle technique. Construction of an impossible differential with the miss-in-the middle technique requires concatenation of two probability one truncated differentials with contradiction in the middle.