The bit-pattern integral attack of reduced-round AC block cipher

A new way to cryptanalysis the AC block cipher is presented in this document. The AC block cipher is based upon the bit-slice technology. By using the bit-pattern integral attack, a 2-round integral distinguisher can be get; then using this distinguisher can attack on 3-round of AC block cipher. It is shown that the full subkey of 3-round AC can be recovered with 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12.5</sup> chosen plaintexts and 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">56</sup> partial decryptions. Therefore, 3-round AC is not immune to bit-pattern integral attack. Moreover, our attack has the lowest memory requirements compared to existing attack on AC.