src/ScharedSecret.java

   1 import java.io.IOException;
   2 import java.sql.Time;
   3 import java.util.Random;
   4
   5 public class ScharedSecret {
   6         static Random rand=new Random();
   7
   8         public static int r10(){
   9                 return rand.nextInt(10);
  10         }
  11
  12         public static int[] encodeBit(boolean bit){
  13                 int threshold=22;
  14                 int dist=3;
  15
  16                 int low = threshold-dist;
  17                 int high = threshold+dist;
  18
  19                 int d1,d2,d3,d4,d5;
  20                 //System.out.println("\nbit: "+(bit?1:0));
  21                         if (bit){
  22                                 //System.out.println("bounds: ["+threshold+"..."+high+"]");
  23                                 d1=r10();
  24                                 while(d1+18<threshold) d1=r10();
  25                                 //System.out.println("d1 = "+d1);
  26
  27                                 d2=r10();
  28                                 while (d1+d2+9<threshold||d1+d2>high) d2=r10();
  29                                 //System.out.println("d2 = "+d2);
  30
  31                                 d3=r10();
  32                                 while (d1+d2+d3<threshold||d1+d2+d3>high)d3=r10();
  33                                 //System.out.println("d3 = "+d3);
  34
  35                                 d4=r10();
  36                                 while (d1+d2+d3+d4 > high) d4=r10();
  37                                 //System.out.println("d4 = "+d4);
  38
  39                                 d5=r10();
  40                                 while (d1+d2+d3+d4+d5 > high) d5=r10();
  41                                 //System.out.println("d5 = "+d5);
  42
  43
  44                         } else {
  45                                 //System.out.println("bounds: ["+low+"..."+threshold+"]");
  46                                 d1=r10();
  47                                 while(d1+18<low) d1=r10();
  48                                 //System.out.println("d1 = "+d1);
  49
  50                                 d2=r10();
  51                                 while (d1+d2+9<low) d2=r10();
  52                                 //System.out.println("d2 = "+d2);
  53
  54                                 d3=r10();
  55                                 while (d1+d2+d3>threshold||d1+d2+d3<low)d3=r10();
  56                                 //System.out.println("d3 = "+d3);
  57
  58                                 d4=r10();
  59                                 while (d1+d2+d3+d4>threshold||d1+d2+d3+d4<low) d4=r10();
  60                                 //System.out.println("d4 = "+d4);
  61
  62                                 d5=r10();
  63                                 while (d1+d2+d3+d4+d5 > threshold||d1+d2+d3+d4+d5<low) d5=r10();
  64                                 //System.out.println("d5 = "+d5);
  65                         }
  66
  67                         //System.out.println(""+d1+d2+d3+d4+d5+" ("+(d1+d2+d3+d4+d5)+")");
  68                 int[] result = {d1,d2,d3,d4,d5};
  69                 return result;
  70         }
  71
  72         public static String[] encodeChar(char c){
  73                 String binary = Integer.toBinaryString(c & 0xFF);
  74
  75                 while (binary.length()<8) binary='0'+binary;
  76                 System.out.print(binary+" ");
  77                 String code1="";
  78                 String code2="";
  79                 String code3="";
  80                 String code4="";
  81                 String code5="";
  82                 for (int i=0; i<8;i++){
  83                         int[] digits = encodeBit(binary.charAt(i)=='1');
  84                         int index = rand.nextInt(4);
  85                         code1+=digits[index];
  86                         if (index!=4)digits[index]=digits[4]; // move last digit to position of used digit
  87
  88                         index = rand.nextInt(3);
  89                         code2+=digits[index];
  90                         if (index!=3)digits[index]=digits[3]; // move last digit to position of used digit
  91
  92                         index = rand.nextInt(2);
  93                         code3+=digits[index];
  94                         if (index!=2)digits[index]=digits[2]; // move last digit to position of used digit
  95
  96                         index = rand.nextInt(1);
  97                         code4+=digits[index];
  98                         code5+=digits[1-index];
  99                 }
 100                 String[] result = {code1,code2,code3,code4,code5};
 101                 return result;
 102         }
 103
 104         private static String secret(String[] args){
 105                 if (args != null && args.length > 0) return args[0];
 106
 107                 try {
 108                         String secret = "";
 109                         System.out.println("Please enter your secret:");
 110                         int c;
 111                         while ((c = System.in.read()) != 10){
 112                                 secret+=(char)c;
 113                         }
 114                         return secret;
 115                 } catch (IOException e) {
 116                         e.printStackTrace();
 117                         System.exit(1);
 118                 }
 119                 return null;
 120         }
 121
 122         public static void main(String[] args) {
 123                 String secret = secret(args);
 124                 String [] codes = { "", "", "", "", "" };
 125                 System.out.print("  Binary: ");
 126                 for (int i=0; i<secret.length();i++){
 127                         String[] chars = encodeChar(secret.charAt(i));
 128                         for (int j = 0; j<5; j++) codes[j] += chars[j]+" ";
 129                 }
 130                 System.out.println();
 131
 132                 for (int j=0; j<5; j++) System.out.println("\nSecret "+j+": "+codes[j]);
 133                 System.out.print("\nChecksum: ");
 134                 for (int i=0; i<codes[0].length(); i++){
 135
 136                         if (i%9==8) {
 137                                 System.out.print(" ");
 138                         } else {
 139                                 System.out.print((codes[0].charAt(i)
 140                                                                                                  +codes[1].charAt(i)
 141                                                                                                  +codes[2].charAt(i)
 142                                                                                                  +codes[3].charAt(i)
 143                                                                                                  +codes[4].charAt(i))>(240+22)?1:0);
 144                         }
 145                 }
 146         }
 147 }