檢視模板:資訊安全:SDES 的原始碼

===Simplified DES===

* [http://sdrv.ms/YX9S0s S-DES教學]
* [http://sdrv.ms/125igf1 S-DES填空表單]
Simplified DES (S-DES) has similar properties and structure to DES with much smaller parameters (See following S-DES scheme).

====s-DES Scheme(S-DES 圖解)====

[[File:S-DES Scheme.png|600px]]

====s-DES 金鑰產生過程====
Following is the key generation process:


[[File:Key Generation for S-DES.png|600px]]

====s-DES加密過程====
Encryption:

[[File:S-DES Encryption Detail.png|600px]]

====S-DES的Java程式====
<source lang="c">
 public class sdes{
  private static short[] plainText={0,0,0,0,0,0,0,0}; //明文空間，將輸入的8位元一一放入此short陣列(為求運算方便)
  private static short[] Key1 ={1,0,1,0,0,1,0,0}; //子金鑰1
  private static short[] Key2 ={0,1,0,0,0,0,1,1};//子金鑰2

  private static short[] bitIndex={128,64,32,16,8,4,2,1};

  private static char[] IP =  {'1','5','2','0','3','7','4','6'};  //"26314857";
  private static char[] IP1 = {'3','0','2','4','6','1','7','5'};  //"41357286";
  private static char[] EP =  {'3','0','1','2','1','2','3','0'};  //"41232341";
  private static char[] P4 =  {'1','3','2','0'};      //"2431";
  private static char[] SW =  {'4','5','6','7','0','1','2','3'};  //"56781234";
  private static char[] P8 =  {'5','2','6','3','7','4','9','8'};  //637485A9";
  private static char[] P10 = {'2','4','1','6','3','9','0','8','7','5'}; //35274A1986";

  private static short[][] S0 = {{1,0,3,2},
                                 {3,2,1,0},
                                 {0,2,1,3},
                                 {3,1,3,2}};

  private static short[][] S1 = {{0,1,2,3},
                                 {2,0,1,3},
                                 {3,0,1,0},
                                 {2,1,0,3}};


  private static short[] tempText = {0,0,0,0,0,0,0,0};

  private static void printText(short[] Text){
    int i;
    for(i=0;i<8;i++) System.out.print(Text[i]);
    System.out.println();
  }

  public static void fx(short[] PT, short[] Key){
    int i,r,c,s;
    short[] leftText = {0,0,0,0};
    short[] rightText = {0,0,0,0};
    short[] fText = {0,0,0,0,0,0,0,0};
    short[] temp4Text = {0,0,0,0};

    for(i=4;i<8;i++) rightText[i-4] = PT[i]; //extract right part of plaintext

//perform EP
    for(i=0; i<8; i++) tempText[i] = rightText[(short)EP[i]-48];
    for(i=0; i<8; i++) fText[i] = tempText[i];
    System.out.print("After E/P : ");printText(fText);       

    for(i=0; i<8; i++) fText[i] ^= Key[i]; //Xor!
    System.out.print("Key is "); printText(Key);
    System.out.print("After XOR with Key : ");printText(fText);

    for(i=0;i<4;i++) leftText[i] = fText[i];    
    for(i=4;i<8;i++) rightText[i-4] = fText[i];

//perform S0 and S1
    r = (leftText[0]<<1) + leftText[3]; System.out.print("S0, Row is "+r+",");
    c = (leftText[1]<<1) + leftText[2]; System.out.print("Col is "+c+" ");
    s = S0[r][c];
    System.out.println("S0 is "+s);
    temp4Text[0] = ((s&2) == 0)? (short)0:(short)1;
    temp4Text[1] = ((s&1) == 0)? (short)0:(short)1; 

    r = (rightText[0]<<1) + rightText[3]; System.out.print("S1, Row is "+r+",");
    c = (rightText[1]<<1) + rightText[2]; System.out.print("Col is "+c+" ");
    s = S1[r][c];
    System.out.println("S1 is "+s);
    temp4Text[2] = ((s&2) == 0)? (short)0:(short)1;
    temp4Text[3] = ((s&1) == 0)? (short)0:(short)1;

//Perform P4
    for(i=0; i<4; i++) tempText[i] = temp4Text[(short)P4[i]-48];
    for(i=0; i<4; i++) temp4Text[i] = tempText[i];
    System.out.print("Apply P4 ");
    for(i=0; i<4; i++) System.out.print(temp4Text[i]);
    System.out.println();

    for(i=0; i<4; i++) leftText[i] = PT[i];

//Xor left and right processed with F-Box
    System.out.print("After XOR with the left part(See the above of diagram):");
    for(i=0; i<4; i++) {
      leftText[i] ^= temp4Text[i];
      System.out.print(leftText[i]);
    }
    System.out.println();
    for(i=0; i<4; i++) PT[i] = leftText[i];


  }

  public static void main(String args[]){
    short plainInt,i;
    if (args.length == 0) System.exit(0);
    plainInt = Short.parseShort(args[0]); //將將輸入的明文字串轉換成short

    for (i=0; i<8; i++) plainText[i] = ((plainInt & bitIndex[i])== 0) ? (short)0 : (short)1; //將明文數字中的每一個位元一一抓取出來測試，設定明文陣列
    System.out.print("The plaintext is "); printText(plainText);

//Perform IP operation
    for(i=0; i<8; i++) tempText[i] = plainText[(short)IP[i]-48];
    for(i=0; i<8; i++) plainText[i] = tempText[i];
    System.out.print("plaintexst after IP is ");
    printText(plainText);

//Round 1   

  System.out.println("Round 1..... ");
  fx(plainText, Key1);
  System.out.print("After round1, the plaintext is ");printText(plainText);

//Perform SW
    for(i=0; i<8; i++) tempText[i] = plainText[(short)SW[i]-48];
    for(i=0; i<8; i++) plainText[i] =  tempText[i];
    System.out.print("After SW, plaintext is ");
    printText(plainText);

//Round 2
  System.out.println("\nRound 2..... ");
  fx(plainText, Key2);
  System.out.print("After round 2, the plaintext is ");printText(plainText);

//Perform IP-1
    for(i=0; i<8; i++) tempText[i] = plainText[(short)IP1[i]-48];
    for(i=0; i<8; i++) plainText[i] =  tempText[i];
    System.out.print("Finally, ciphertext is ");
    printText(plainText);

  }
}
</source>