src/secret.html

   1 <html>
   2 <head>
   3 <style type="text/css">
   4         @media print {
   5                 #pages > div{
   6                         page-break-after: always;
   7                 }
   8
   9                 fieldset{
  10                         display: none;
  11                 };
  12         }
  13
  14         @media screen {
  15                 #pages{
  16                         display: none;
  17                 }
  18         }
  19
  20         td{
  21                 text-align: right;
  22                 padding: 10px;
  23         }
  24         td:nth-child(2n){
  25                 background:#ccc;
  26         }
  27         tr:nth-child(2) td{
  28                 border-width: 0 0 5px 0;
  29                 border-style: solid;
  30
  31         }
  32         .half{
  33                 border: 1px solid black;
  34         }
  35         .num{
  36                 width: 40px;
  37         }
  38
  39         #pages span {
  40         border: 1px solid gray;
  41         display: inline-block;
  42         margin: 3px;
  43         padding: 3px;
  44         }
  45         textarea{
  46                 width: 100%;
  47                 min-height: 150px;
  48         }
  49
  50
  51 </style>
  52 <script type="text/javascript">
  53 var prime=257;
  54 function createElement(e,t){return '<'+e+'>'+t+'</'+e+'>';} // html element with content t
  55 function getElement(i){return document.getElementById(i);}
  56 function setHtmlOf(i,t){getElement(i).innerHTML=t};
  57 function valueOfField(i){return getElement(i).value;} // value of element with id
  58
  59 function rand256(){
  60         return Math.floor(Math.random() * 256);
  61 }
  62
  63 /* Split number into the shares */
  64 function split(number, number_of_shares, needed) {
  65     var coef = [number]
  66     var shares = [];
  67
  68     for(var coef_index = 1; coef_index < needed; coef_index++){
  69         coef[coef_index] = rand256();
  70     }
  71
  72     for(var share_number = 1; share_number <= number_of_shares; share_number++) {
  73         var sum = 0;
  74         for (var coef_index =0; coef_index<needed; coef_index++){
  75                 sum += coef[coef_index]*Math.pow(share_number,coef_index);
  76         }
  77
  78         shares[share_number-1] = sum % prime;
  79     }
  80     return shares;
  81 }
  82
  83 function collect(){
  84         var divs=document.getElementsByClassName('share');
  85         var shares=[],lastValue;
  86         for (var div_index=0; div_index<divs.length; div_index++){
  87                 var div=divs[div_index];
  88                 var inputs = div.getElementsByTagName('input');
  89                 var share_number=0;
  90                 for (var j=0; j<inputs.length;j++){
  91                         var input = inputs[j];
  92                         if (input.className == 'num') {
  93                                 share_number=input.value;
  94                         } else {
  95                                 string=input.value;
  96                                 if (share_number>0 && string!='') {
  97                                         var parts = string.split(' ');
  98                                         shares[div_index] = { share_number, parts };
  99                                 }
 100                         }
 101                 }
 102         }
 103         if (string!=''){
 104                 var clone=div.cloneNode(true);
 105                 var inputs=clone.getElementsByTagName('input');
 106                 for (var j=0; j<inputs.length; j++) inputs[j].value='';
 107                 div.parentNode.appendChild(clone);
 108         }
 109         return shares;
 110 }
 111
 112 function gcdD(a,b) {
 113     if (b == 0) return [a, 1, 0];
 114     else {
 115         var n = Math.floor(a/b), c = a % b, r = gcdD(b,c);
 116         return [r[0], r[2], r[1]-r[2]*n];
 117     }
 118 }
 119
 120 function modInverse(k) {
 121     k = k % prime;
 122     var r = (k < 0) ? -gcdD(prime,-k)[2] : gcdD(prime,k)[2];
 123     return (prime + r) % prime;
 124 }
 125
 126 function join(shares) {
 127     var sum = 0;
 128
 129     for(j = 0; j < shares.length; j++) {
 130         var numerator = 1;
 131         var denominator = 1;
 132         for(m = 0; m < shares.length; m++) {
 133             if(j == m) continue; // If not the same value
 134             numerator = (numerator * shares[m].share_number) % prime;
 135             denominator = (denominator * (shares[m].share_number - shares[j].share_number)) % prime;
 136         }
 137         sum = (prime + sum + (shares[j].share * numerator * modInverse(denominator))) % prime;
 138     }
 139
 140     return sum;
 141 }
 142
 143 function decode(){
 144         var shares_list=collect(); // fetch shares
 145         var codeCount=null;
 146         for (var i=0; i<shares_list.length; i++) {
 147                 if (codeCount == null){
 148                         codeCount = shares_list[i].parts.length;
 149                 } else {
 150                         codeCount=Math.min(shares_list[i].parts.length,codeCount);
 151                 }
 152         }
 153
 154         var ascii=document.getElementById('ascii');
 155         ascii.innerHTML='ascii: ';
 156         result.innerHTML='Passphrase: ';
 157
 158
 159         for (var codeIndex = 0; codeIndex<codeCount; codeIndex++){
 160                 shares_for_code = [];
 161                 for (var share_index=0; share_index<shares_list.length; share_index++){
 162                         var share_number = shares_list[share_index].share_number;
 163                         var share = shares_list[share_index].parts[codeIndex];
 164                         shares_for_code[share_index] = { share_number, share };
 165                 }
 166
 167                 var code = join(shares_for_code);
 168                 ascii.innerHTML += code+' ';
 169                 result.innerHTML+= String.fromCharCode(code);
 170
 171         }
 172 }
 173
 174 function secret2numbers(string){
 175         var string_pos,share_number,coef,char_code,x,sum;
 176         var number_of_shares = valueOfField('shares');
 177         var treshold             = valueOfField('treshold');
 178         var results = [];
 179
 180         // create table elements for displaying the shares
 181         var char_cells      = createElement('th','char');;
 182         var char_code_cells = createElement('th','ascii');;
 183
 184         // decompose string, for each character create secrets from asccii code
 185         for (string_pos=0; string_pos<string.length;string_pos++) {
 186                 char_code        = string.charCodeAt(string_pos);
 187                 char_cells      += createElement('td',string[string_pos]);
 188                 char_code_cells += createElement('td',char_code);
 189
 190                 results[string_pos] = split(char_code,number_of_shares,treshold);
 191         }
 192
 193         var code=createElement('tr',char_cells)+createElement('tr',char_code_cells);
 194         var pages=getElement('pages');
 195         var explanation=valueOfField('explanation').replace('%n',valueOfField('treshold')).replace(/\n/g,'<br/>');
 196         pages.innerHTML='';
 197         for (share_number=0;share_number<number_of_shares;share_number++){
 198                 var line=createElement('th','share '+(share_number+1));
 199                 var page='';
 200                 for (string_pos=0;string_pos<string.length;string_pos++){
 201                         line+=createElement('td',results[string_pos][share_number]);
 202                         page+=createElement('span',results[string_pos][share_number]);
 203                 }
 204                 code+=createElement('tr',line);
 205                 pages.innerHTML+=createElement('div',  createElement('p',explanation)+createElement('p','Your share number: '+(share_number+1))+createElement('p',page)   );
 206         }
 207         setHtmlOf('tab',code);
 208         return char_code;
 209 }
 210 </script>
 211 </head>
 212 <body>
 213         <fieldset>
 214                 <legend>Decode secret from shares</legend>
 215                 <div>
 216                         <div class="share">
 217                                 Share #<input class="num" value="1" />: <input class="code" onkeyup="decode();"/>
 218                         </div>
 219                 </div>
 220                 <p id="ascii"></p>
 221                 <p id="result"></p>
 222         </fieldset>
 223         <fieldset>
 224                 <legend>Create shares from secret</legend>
 225                 Explanation to add:<br/>
 226                 <textarea id="explanation" name="explanation">
 227 This document is a PART of a secret passphrase. At least %n of these secret parts are required to reconstruct the original passphrase.
 228 In the event of (enter condition here), you may meet with other secret-part holders to unite your keys.
 229
 230 To obtain the secret phassphrase:
 231 <ol>
 232         <li>collect at least %n secret shares</li>
 233         <li>go to [url of this page]</li>
 234         <li>enter the share number and the respective numbers separated by spaces</li>
 235 </ol>
 236 The passphrase obtained will give you access to [insert description of secured thing here...].
 237
 238 [More instructions]
 239
 240 Info: These secrets were generated using the "Shamir's Secret Sharing" algorithm.
 241                 </textarea><br/>
 242                 Passphrase parts to generate: <input id="shares" value="5" /></br>
 243                 Minimum nuber of shares required to recreate secret: <input id="treshold" value="3" /></br>
 244                 Secret: <input name="secret" onkeyup="secret2numbers(this.value);" />
 245                 <table id="tab"></table>
 246                 <ol>
 247                 <li>Set the explanation you want.</li>
 248                 <li>Enter the number of parts and shares you wish.</li>
 249                 <li>Enter your secret passphrase</li>
 250                 <li>Hit Ctrl+P or go to print via the menu</li>
 251                 </ol>
 252         </fieldset>
 253         <div id="pages"></div>
 254 </body>
 255 </html>