added question.min

helios/templates/election_build.html

@@ -1,7 +1,7 @@
 {% extends "base.html" %}
 
 {% block content %}
-  <h2 class="title">{{utils.get_host}} {{election.name}} &mdash; Build <span style="font-size:0.7em;">[<a href="./view">done</a>]</span></h2>
+  <h2 class="title">{{election.name}} &mdash; Build <span style="font-size:0.7em;">[<a href="./view">done</a>]</span></h2>
 
   <script language="javascript">
     Helios.setup();
@@ -59,6 +59,7 @@ <h2 class="title">{{utils.get_host}} {{election.name}} &mdash; Build <span style
       question['question'] = form['question'].value;
 
       // integer
+      question['min'] = parseInt(form['min'].value);
       question['max'] = parseInt(form['max'].value);
 
       $(question.answers).each(function(i, answer) {

helios/templates/vote.html

@@ -69,6 +69,23 @@ <h3>Fingerprint: <span id="election_hash"></span></h3>
   BOOTH.show($('#election_div')).processTemplate({'election' : BOOTH.election});
 };
 
+// check if the current question is ok
+BOOTH.validate_question = function(question_num) {
+    // check if enough answers are checked
+    if (BOOTH.ballot.answers[question_num].length < BOOTH.election.questions[question_num].min) {
+        alert('You need to select at least ' + BOOTH.election.questions[question_num].min + ' answer(s).');
+        return false;
+    }
+
+    return true;
+};
+
+BOOTH.validate_and_confirm = function(question_num) {
+  if (BOOTH.validate_question(question_num)) {
+      BOOTH.show_confirm();
+  }
+};
+
 BOOTH.show_question = function(question_num) {
   BOOTH.show_progress('1');
   BOOTH.show($('#question_div')).processTemplate({'question_num' : question_num, 

static/bigint.js

@@ -13,7 +13,6 @@
 BigInt = Class.extend({
   init: function(value, radix) {
     if (value == null) {
-      debugger;
       throw "null value!";
     }
 

static/elgamal.js

@@ -246,6 +246,7 @@ ElGamal.Ciphertext = Class.extend({
     // go through all plaintexts and simulate the ones that must be simulated.
     // note how the interface is as such so that the result does not reveal which is the real proof.
     var self = this;
+
     var proofs = $(list_of_plaintexts).map(function(p_num, plaintext) {
       if (p_num == real_index) {
         // no real proof yet
@@ -268,6 +269,7 @@ ElGamal.Ciphertext = Class.extend({
       var commitments = $(proofs).map(function(proof_num, proof) {
         return proof.commitment;
       });
+
       var disjunctive_challenge = challenge_generator(commitments);
 
       // now we must subtract all of the other challenges from this challenge.
@@ -283,7 +285,7 @@ ElGamal.Ciphertext = Class.extend({
 
     // set the real proof
     proofs[real_index] = real_proof;
-
+        
     return new ElGamal.DisjunctiveProof(proofs);
   },
 

static/helios.js

@@ -146,15 +146,19 @@ UTILS.open_window_with_content = function(content) {
 };
 
 // generate an array of the first few plaintexts
-UTILS.generate_plaintexts = function(pk, num) {
+UTILS.generate_plaintexts = function(pk, min, max) {
   var last_plaintext = BigInt.ONE;
 
   // an array of plaintexts
-  var plaintexts = []
+  var plaintexts = [];
+
+  if (min == null)
+    min = 0;
 
   // questions with more than one possible answer, add to the array.
-  for (var i=0; i<=num; i++) {
-    plaintexts[i] = new ElGamal.Plaintext(last_plaintext, pk, false);
+  for (var i=0; i<=max; i++) {
+    if (i >= min)
+      plaintexts.push(new ElGamal.Plaintext(last_plaintext, pk, false));
     last_plaintext = last_plaintext.multiply(pk.g).mod(pk.p);
   }
 
@@ -191,8 +195,9 @@ HELIOS.EncryptedAnswer = Class.extend({
     var individual_proofs = [];
     var overall_proof = null;
 
-    // possible plaintexts [0, 1, .. , question.max]
-    var plaintexts = UTILS.generate_plaintexts(pk, question.max);
+    // possible plaintexts [question.min .. , question.max]
+    var plaintexts = UTILS.generate_plaintexts(pk, question.min, question.max);
+    var zero_one_plaintexts = UTILS.generate_plaintexts(pk, 0, 1);
 
     // keep track of whether we need to generate new randomness
     var generate_new_randomness = false;    
@@ -220,12 +225,12 @@ HELIOS.EncryptedAnswer = Class.extend({
         randomness[i] = Random.getRandomInteger(pk.q);        
       }
 
-      choices[i] = ElGamal.encrypt(pk, plaintexts[plaintext_index], randomness[i]);
+      choices[i] = ElGamal.encrypt(pk, zero_one_plaintexts[plaintext_index], randomness[i]);
 
       // generate proof
       if (generate_new_randomness) {
         // generate proof that this ciphertext is a 0 or a 1
-        individual_proofs[i] = choices[i].generateDisjunctiveProof(plaintexts, plaintext_index, randomness[i], ElGamal.disjunctive_challenge_generator);        
+        individual_proofs[i] = choices[i].generateDisjunctiveProof(zero_one_plaintexts, plaintext_index, randomness[i], ElGamal.disjunctive_challenge_generator);        
       }
 
       if (progress)
@@ -245,7 +250,14 @@ HELIOS.EncryptedAnswer = Class.extend({
 
       // prove that the sum is 0 or 1 (can be "blank vote" for this answer)
       // num_selected_answers is 0 or 1, which is the index into the plaintext that is actually encoded
-      overall_proof = hom_sum.generateDisjunctiveProof(plaintexts, num_selected_answers, rand_sum, ElGamal.disjunctive_challenge_generator);
+      //
+      // now that "plaintexts" only contains the array of plaintexts that are possible starting with min
+      // and going to max, the num_selected_answers needs to be reduced by min to be the proper index
+      var overall_plaintext_index = num_selected_answers;
+      if (question.min)
+        overall_plaintext_index -= question.min;
+
+      overall_proof = hom_sum.generateDisjunctiveProof(plaintexts, overall_plaintext_index, rand_sum, ElGamal.disjunctive_challenge_generator);
       if (progress)
         progress.tick();
     }
@@ -409,7 +421,7 @@ HELIOS.EncryptedVote = Class.extend({
   },
 
   verifyProofs: function(pk, outcome_callback) {
-    var zero_or_one = UTILS.generate_plaintexts(pk, 1);
+    var zero_or_one = UTILS.generate_plaintexts(pk, 0, 1);
 
     var VALID_P = true;
 
@@ -431,7 +443,7 @@ HELIOS.EncryptedVote = Class.extend({
         });
 
         // possible plaintexts [0, 1, .. , question.max]
-        var plaintexts = UTILS.generate_plaintexts(pk, self.election.questions[ea_num].max);
+        var plaintexts = UTILS.generate_plaintexts(pk, self.election.questions[ea_num].min, self.election.questions[ea_num].max);
 
         // check the proof on the overall product
         var overall_check = overall_result.verifyDisjunctiveProof(plaintexts, enc_answer.overall_proof, ElGamal.disjunctive_challenge_generator);

static/templates/booth/question.html

@@ -1,13 +1,18 @@
 
-<h3 style="border-bottom: 1px solid black;">Question #{$T.question_num + 1} </h3>
+<h3 style="border-bottom: 1px solid black;">Question #{$T.question_num + 1} of {$T.last_question_num + 1}</h3>
 
 <form onsubmit="return false;" class="prettyform" id="answer_form">
 <input type="hidden" name="question_num" value="{$T.question_num}" />
 
 <p>
 <em>{$T.question.question}</em>
-
- (select {$T.question.max} answer{#if $T.question.max > 1}s{#/if})
+<br />
+<span style="font-size: 0.6em;">(select 
+{#if $T.question.min && $T.question.min > 0}
+at least {$T.question.min} answer{#if $T.question.min > 1}s{#/if}, 
+{#/if} 
+up to {$T.question.max} answer{#if $T.question.max > 1}s{#/if})
+</span>
 </p>
 
 
@@ -24,16 +29,16 @@ <h3 style="border-bottom: 1px solid black;">Question #{$T.question_num + 1} </h3
 {#/for}
 
 <div style="float: right;">
-<input type="button" onclick="BOOTH.show_confirm();" value="Review all Choices" />
+<input type="button" onclick="BOOTH.validate_and_confirm({$T.question_num});" value="Review all Choices" />
 </div>
 
 {#if $T.question_num != 0}
-<input type="button" onclick="BOOTH.show_question({$T.question_num -1});" value="Previous" />
+<input type="button" onclick="if (BOOTH.validate_question({$T.question_num})) {BOOTH.show_question({$T.question_num -1});}" value="Previous" />
 &nbsp;
 {#/if}
 
 {#if $T.question_num < $T.last_question_num}
-<input type="button" onclick="BOOTH.show_question({$T.question_num +1});" value="Next" />
+<input type="button" onclick="if (BOOTH.validate_question({$T.question_num})) {BOOTH.show_question({$T.question_num +1});}" value="Next" />
 &nbsp;
 {#/if}
 

static/templates/builder/question.html

@@ -15,6 +15,9 @@ <h4>New Question</h4>
 <label for="question">Full Question:</label>
 <textarea name="question" id="question" cols="40" rows="3" wrap="soft">{$T.question.question}</textarea><br />
 
+<label for="max">Min # of Answers:</label>
+<input type="text" name="min" id="min" size="3" value="{$T.question.min || 0}" /><br />
+
 <label for="max">Max # of Answers:</label>
 <input type="text" name="max" id="max" size="3" value="{$T.question.max || 1}" /><br />
 <!--<input type="hidden" name="max" id="max" value="1" />-->