encryption.java~140~

用JAVA编写的用密码学中DES算法加密解密文件的程序

    for(int i=0; i<16; i++)
    {
      passIP+=textInBi.charAt(IP[i]-1);
    }
    System.out.println("****************************passIP is "+passIP);
    g1=passIP.substring(0,8);
    g2=passIP.substring(8,16);
    //first pass F and combine
    passF=functionF(g1,subkey1);
    System.out.println("**********************pass function F1 is "+passF);
    passCombine1=combine(passF,g2);
    System.out.println("*************************passCombine1 is "+passCombine1);
    //second pass F and combine
    passF=functionF(passCombine1,subkey2);
    System.out.println("****************************pass function F2 is "+passF);
    passCombine2=combine(passF,g1);
    System.out.println("******************************passCombine2 is "+passCombine2);
    //concate two subString with 8 bits
    beforeIP_1=passCombine1+passCombine2;
    System.out.println("the length of before IP-1 is "+beforeIP_1.length());
    for(int i=0; i<16; i++)
    {
      passIP_1+=beforeIP_1.charAt(IP_1[i]-1);
    }
    System.out.println("passIP_1 is"+passIP_1);
    subEncry=biToText(passIP_1);
    return subEncry;
  }

  public String biToText(String bi)
  {
    String text="";
    String subBi="";
    int biToD=0;
    System.out.println("bi is "+bi+" the length is "+bi.length());
    for(int i=0; i<bi.length();i++)
    {
      subBi=bi.substring(i,i+8);
      System.out.println("subString "+i+" is "+subBi);
      i+=7;
      biToD=Integer.parseInt(convertBToD(subBi));
      System.out.println("decimal "+i+" is"+biToD);
      text+=(char)biToD;
      System.out.println("subtext is "+text);
    }
    return text;
  }

  public String textToBi(String subText)
  {
    String bi="";
    String sub1="";
    String sub2="";
    int c1=subText.charAt(0);
    int c2=subText.charAt(1);

    sub1=convertDToB(c1,8);
    System.out.println("sub1 is "+sub1);
    sub2=convertDToB(c2,8);
    bi=sub1+sub2;
    System.out.println("&&&&&&&&&&&&&&&&&&&&&&&key is "+bi);
    return bi;
  }

  public String functionF(String R, String subkey)
  {
    String E="812345456781";
    String P="64735182";
    String passE="";
    String passCombine="";

    String passSBox1="";
    String passSBox2="";
    String passSBox="";
    String passP="";
    //R pass E
    for(int i=0; i<12; i++)
    {
      passE+=R.charAt(Integer.parseInt(E.substring(i,i+1))-1);
    }

    //E pass combination
    passCombine+=combine(passE, subkey);

    //get two substirng with 6 digits
    String beforeSBox1=passCombine.substring(0,6);
    String beforeSBox2=passCombine.substring(6,12);

    //get two substring with 4 digits
    passSBox1=passSBox(1,beforeSBox1);
    passSBox2=passSBox(2,beforeSBox2);

    //print out combine
    System.out.println("box1 is ");
    for(int i=0; i<passSBox1.length();i++)
    {
      System.out.print(passSBox1.charAt(i));
    }
    //print out combine
    System.out.println("SBox2 is ");
    for(int i=0; i<passSBox2.length();i++)
    {
      System.out.print(passSBox2.charAt(i));
    }

    //concate two substring into one
    passSBox=passSBox1+passSBox2;

    //pass P
    for(int i=0; i<passSBox.length(); i++)
    {
      passP+=passSBox.charAt(Integer.parseInt(P.substring(i,i+1))-1);

    }
    return passP;
  }

  public String combine(String G1, String G2)
  {
    String combine="";
    if(G1.length()==G2.length())
    {
      for(int i=0; i<G1.length(); i++)
      {
        combine+=XOR(G1.charAt(i),G2.charAt(i));
      }
    }
    return combine;
  }

  public char XOR(char a, char b)
  {
    char c;
    if(a==b)
        c='0';
    else
        c='1';
    return c;
  }

  //subString with 6 bits to pass box to get a string with 4 digits
  public String passSBox(int box, String beforeBox)
  {
    String afterBox="";

    //get row number in binary
    String row=beforeBox.substring(0,1);
    row+=beforeBox.charAt(5);

    //get colum number in binary
    String colum="";
    for(int i=1; i<=4;i++)
    {
      colum+=beforeBox.charAt(i);
    }

    //convert binary to decimal to get row and colum in s-box
    String inBoxRow=convertBToD(row);
    String inBoxColum=convertBToD(colum);
    int iRow=Integer.parseInt(inBoxRow);
    int iColum=Integer.parseInt(inBoxColum);
    afterBox=inSBox(box,iRow,iColum);
    return afterBox;
  }

  //convert binary to decimal
  public String convertBToD(String a)
  {
    int ctr=1, decimal=0;
    for (int i = a.length()-1; i>=0; i--)
    {
      if(a.charAt(i)=='1')
        decimal+=ctr;
      ctr*=2;
    }
    String converted = "" + decimal;
    return converted;
  }

  //find the number in S-Box
  public String inSBox(int box, int row, int colum)
  {
    int boxNum=0;
    String bin;
    int[][] SBox1=
    {
      {14, 4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7},
      {0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8},
      {4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0},
      {15, 12, 8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13},
    };
    int[][] SBox2=
    {
      {15, 1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10},
      {3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5},
      {0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15},
      {13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14, 9},
    };
    if(box==1)
      boxNum=SBox1[row][colum];
    if(box==2)
      boxNum=SBox2[row][colum];
    //get binary with 4 digits in string from s-box
    bin=convertDToB(boxNum,4);
    return bin;
  }

  //convert decimal number into binary in String
  public String convertDToB (int deci,int bits)
  {
    String bi="";
    //convert decimal into binary
    while (deci>=1)
    {
      if(deci%2==0)
        bi+="0";
      if(deci%2==1)
        bi+="1";
      deci/=2;
    }
    if(bits==4)
    {
      //let String bi has four digits
      while (bi.length() != 4)
      {
        bi += "0";
      }
    }
    if(bits==8)
     {
       //let String bi has four digits
       while (bi.length() != 8)
       {
         bi += "0";
       }
     }

    bi=inverse(bi);
    return bi;
  }

//inverse binary order
  public String inverse(String oldS)
  {
    String newS="";
    for(int i=oldS.length()-1; i>=0; i--)
    {
      newS+=oldS.charAt(i);
    }
    return newS;
  }

  //calculate two subkeys
  public  String[] calSubKey(String Key)
 {
   String[] subKey = new String[2];
  //PC1 condition
  int[] PC1 = {11,15,4,13,7,9,3,
               2,5,14,6,10,12,1};

  int[] PC2 = {6,11,4,8,13,3,
               12,5,1,10,2,9};
  //the key After PC1
  String passKey1= "";

  //the subKey1 and subKey2
  String subKey1 = "";
  String subKey2 = "";

  //the result of key after PC1
  for(int i=0;i<PC1.length;i++)
  {
    passKey1 += Key.charAt(PC1[i]-1);
  }

  //Divide the result into left bits(cKey) and right bits(dKey)
  String cKey = passKey1.substring(0,7);
  String dKey = passKey1.substring(7);

  //Calculate subKey1-------------------------------
  //Shift to the right at 2 positions for both c and d
  String c1Key = cKey.substring(5)+cKey.substring(0,5);
  String d1Key = dKey.substring(5)+dKey.substring(0,5);

  //combine c1 and d1
  String tempKey1 = "";
  tempKey1 = c1Key + d1Key;

  //after PC2,get K1
  for(int i=0;i<PC2.length;i++)
  {
    subKey1+=tempKey1.charAt(PC2[i]-1);
  }

  //Calculate subKey2----------------------------------
  //Shift to the right at 2 positions for both c1 and d1
  String c2Key = c1Key.substring(5)+c1Key.substring(0,5);
  String d2Key = d1Key.substring(5)+d1Key.substring(0,5);

  //combine c2 and d2
  String tempKey2 = "";
  tempKey2 = c2Key + d2Key;

  //pass PC2 , get k2
  for(int i=0;i<PC2.length;i++)
  {
    subKey2+=tempKey2.charAt(PC2[i]-1);
  }

  subKey[0] = subKey1;
  subKey[1] = subKey2;
  return subKey;
 }
}