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Entropy library assumes cards are discarded

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and removed the duplicate logic from the UI logic.
This commit is contained in:
Ian Coleman
2016-11-17 14:28:26 +11:00
parent bbc29c80f4
commit 6422c1cd57
3 changed files with 81 additions and 67 deletions
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src/js/entropy.js
+46
View File
@@ -117,6 +117,40 @@ window.Entropy = new (function() {
while (entropyBin.length < expectedBits) {
entropyBin = "0" + entropyBin;
}
// Assume cards are NOT replaced.
// Additional entropy decreases as more cards are used. This means
// entropy is measured using n!, not base^n.
// eg the second last card can be only one of two, not one of fifty two
// so the added entropy for that card is only one bit at most
if (base.asInt == 52) {
// Get the maximum value without replacement
var totalDecks = Math.ceil(base.parts.length / 52);
var totalCards = totalDecks * 52;
var totalCombos = factorial(52).pow(totalDecks);
var totalRemainingCards = totalCards - base.parts.length;
var remainingDecks = Math.floor(totalRemainingCards / 52);
var remainingCards = totalRemainingCards % 52;
var remainingCombos = factorial(52).pow(remainingDecks).multiply(factorial(remainingCards));
var currentCombos = totalCombos.divide(remainingCombos);
var numberOfBits = Math.log2(currentCombos);
var maxWithoutReplace = BigInteger.pow(2, numberOfBits);
// aggresive flooring of numberOfBits by BigInteger.pow means a
// more accurate result can be had for small numbers using the
// built-in Math.pow function.
if (numberOfBits < 32) {
maxWithoutReplace = BigInteger(Math.round(Math.pow(2, numberOfBits)));
}
// Get the maximum value with replacement
var maxWithReplace = BigInteger.pow(52, base.parts.length);
// Calculate the new value by scaling the original value down
var withoutReplace = entropyInt.multiply(maxWithoutReplace).divide(maxWithReplace);
// Left pad with zeros based on number of bits
var entropyBin = withoutReplace.toString(2);
var numberOfBitsInt = Math.floor(numberOfBits);
while (entropyBin.length < numberOfBitsInt) {
entropyBin = "0" + entropyBin;
}
}
// Supply a 'filtered' entropy string for display purposes
var entropyClean = base.parts.join("");
var entropyHtml = base.parts.join("");
@@ -221,4 +255,16 @@ window.Entropy = new (function() {
return BigInteger.log(x) / BigInteger.log(2);
};
// Depends on BigInteger
function factorial(n) {
if (n == 0) {
return 1;
}
f = BigInteger.ONE;
for (var i=1; i<=n; i++) {
f = f.multiply(new BigInteger(i));
}
return f;
}
})();
src/js/index.js
+10 -42
View File
@@ -791,20 +791,21 @@
}
function showEntropyFeedback(entropy) {
var numberOfBits = entropy.binaryStr.length;
var strength = "extremely weak";
if (entropy.binaryStr.length >= 64) {
if (numberOfBits >= 64) {
strength = "very weak";
}
if (entropy.binaryStr.length >= 96) {
if (numberOfBits >= 96) {
strength = "weak";
}
if (entropy.binaryStr.length >= 128) {
if (numberOfBits >= 128) {
strength = "strong";
}
if (entropy.binaryStr.length >= 160) {
if (numberOfBits >= 160) {
strength = "very strong";
}
if (entropy.binaryStr.length >= 192) {
if (numberOfBits >= 192) {
strength = "extremely strong";
}
// If time to crack is less than one day, and password is considered
@@ -825,38 +826,17 @@
console.log("Error detecting entropy strength with zxcvbn:");
console.log(e);
}
var bitsStr = getNumberOfEntropyBits(entropy);
var wordCount = Math.floor(entropy.binaryStr.length / 32) * 3;
var entropyTypeStr = getEntropyTypeStr(entropy);
var wordCount = Math.floor(numberOfBits / 32) * 3;
var bitsPerEvent = Math.log2(entropy.base.asInt).toFixed(2);
DOM.entropyFiltered.html(entropy.cleanHtml);
DOM.entropyType.text(entropyTypeStr);
DOM.entropyStrength.text(strength);
DOM.entropyEventCount.text(entropy.base.ints.length);
DOM.entropyBits.text(bitsStr);
DOM.entropyBits.text(numberOfBits);
DOM.entropyWordCount.text(wordCount);
DOM.entropyBinary.text(entropy.binaryStr);
DOM.entropyBitsPerEvent.text(Math.log2(entropy.base.asInt).toFixed(2));
}
function getNumberOfEntropyBits(entropy) {
var bitsStr = entropy.binaryStr.length.toString();
// If using cards, assume they are not reused, thus additional entropy
// decreases as more cards are used. This means entropy is measured
// using n!, not base^n.
// eg the second last card can be only one of two, not one of fifty two
// so the added entropy for that card is only one bit at most
if (entropy.base.asInt == 52) {
var totalDecks = Math.ceil(entropy.base.parts.length / 52);
var totalCards = totalDecks * 52;
var totalCombos = factorial(52).pow(totalDecks);
var totalRemainingCards = totalCards - entropy.base.parts.length;
var remainingDecks = Math.floor(totalRemainingCards / 52);
var remainingCards = totalRemainingCards % 52;
var remainingCombos = factorial(52).pow(remainingDecks) * factorial(remainingCards);
var currentCombos = totalCombos.divide(remainingCombos);
bitsStr = currentCombos.toString(2).length.toString();
}
return bitsStr
DOM.entropyBitsPerEvent.text(bitsPerEvent);
}
function getEntropyTypeStr(entropy) {
@@ -922,18 +902,6 @@
return typeStr;
}
// Depends on BigInteger
function factorial(n) {
if (n == 0) {
return 1;
}
f = BigInteger.ONE;
for (var i=1; i<=n; i++) {
f = f.multiply(new BigInteger(i));
}
return f;
}
var networks = [
{
name: "Bitcoin",