implementation of 4 round impossible differential of AES

Hi,
I'm trying to implement 4 round impossible differential of AES according to [Impossible differential cryptanalysis of 7-round Advanced Encryption Standard (AES) by Raphael C. & -W. Phan].
It seems round 1 & 2 working properly but round 3 & 4 not ok. I'm using java language, my method is as follows.

        public void fourRoundDifferential()
       {
               KeyExpansion();
           for(int i = 0; i < 16; i ++){
               C1[i] = extend_key[i]^P1[i];
                           C2[i] = extend_key[i]^P2[i];
           }
                   for(int r = 1; r < 5 ; r++){
                       System.out.println("\nround-"+r);
                       if(r < 3){//round 1 & 2
                            for(int j = 0; j < 16; j++){
                                C1[j] = SubWord(C1[j]);
                                C2[j] = SubWord(C2[j]);
                            }
                            System.out.print("\n");
                            for(int x = 0; x < 16; x++){
                                System.out.print(" | SB-"+x+", = "+(C1[x]^C2[x]));
                            }
                            ShiftRow1();
                            ShiftRow2();
                            System.out.print("\n");
                            for(int x = 0; x < 16; x++){
                                System.out.print(" | SR-"+x+", = "+(C1[x]^C2[x]));
                            }
                            MixColumn1();
                            MixColumn2();
                            System.out.print("\n");
                            for(int x = 0; x < 16; x++){
                                System.out.print(" | MC-"+x+", = "+(C1[x]^C2[x]));
                            }
                            for(int i = 0; i < 16; i ++){
                                C1[i] = C1[i]^extend_key[r*16+i];
                                C2[i] = C2[i]^extend_key[r*16+i];
                            }
                            System.out.print("\n");
                            for(int x = 0; x < 16; x++){
                                System.out.print(" | AR-"+x+", = "+(C1[x]^C2[x]));
                            }
                       }else
                           if(r >= 3){//round 3 & 4
                                for(int j = 0; j < 16; j++){
                                    C1[j] = invSubWord(C1[j]);
                                    C2[j] = invSubWord(C2[j]);
                                }
                            System.out.print("\n");
                            for(int x = 0; x < 16; x++){
                                System.out.print(" | SB-"+x+", = "+(C1[x]^C2[x]));
                            }
                                invShiftRow1();
                                invShiftRow2();
                            System.out.print("\n");
                            for(int x = 0; x < 16; x++){
                                System.out.print(" | SR-"+x+", = "+(C1[x]^C2[x]));
                            }
                                if(r == 3){
                                    invMixColumn1();
                                    invMixColumn2();
                                    System.out.print("\n");
                                    for(int x = 0; x < 16; x++){
                                        System.out.print(" | MC-"+x+", = "+(C1[x]^C2[x]));
                                    }
                                }

                                for(int i = 0; i < 16; i ++){
                                    C1[i] = C1[i]^extend_key[160-r*16+i];
                                    C2[i] = C2[i]^extend_key[160-r*16+i];
                                }
                            System.out.print("\n");
                            for(int x = 0; x < 16; x++){
                                System.out.print(" | AR-"+x+", = "+(C1[x]^C2[x]));
                            }
                           }
                   }
       }

Edited by WingedPanther, 08 January 2011 - 03:58 PM.
add code tags (the # button)