[Pkg-javascript-commits] [node-miller-rabin] 01/37: lib: initial

[Bastien Roucariès]

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rouca pushed a commit to branch master
in repository node-miller-rabin.

commit 401db8429fe6c01bb403745ed0dec7789b918c8e
Author: Fedor Indutny <fedor at indutny.com>
Date:   Wed Nov 5 12:30:22 2014 -0500

    lib: initial
---
 .gitignore       |  2 ++
 lib/mr.js        | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 package.json     | 34 ++++++++++++++++++++++++++++++++++
 test/api-test.js | 19 +++++++++++++++++++
 4 files changed, 103 insertions(+)

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..1ca9571
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+node_modules/
+npm-debug.log
diff --git a/lib/mr.js b/lib/mr.js
new file mode 100644
index 0000000..4ff6c6f
--- /dev/null
+++ b/lib/mr.js
@@ -0,0 +1,48 @@
+var bn = require('bn.js');
+var brorand = require('brorand');
+
+exports.test = function test(n, k) {
+  var len = n.bitLength();
+  var red = bn.mont(n);
+  var rone = new bn(1).toRed(red);
+
+  // Fermat test
+  if (new bn(2).toRed(red).redPow(n.subn(1)).cmp(rone) !== 0)
+    return false;
+
+  if (!k)
+    k = Math.max(1, (len / 48) | 0);
+
+  // Find d and s, (n - 1) = (2 ^ s) * d;
+  var n1 = n.subn(1);
+  var n2 = n1.subn(1);
+  for (var s = 0; !n1.testn(s); s++) {}
+  var d = n.shrn(s);
+
+  var rn1 = n1.toRed(red);
+
+  var prime = true;
+  for (; k > 0; k--) {
+    do
+      var a = new bn(brorand(Math.ceil(len / 8)));
+    while (a.cmpn(2) < 0 || a.cmp(n2) > 0);
+
+    var x = a.toRed(red).redPow(d);
+    if (x.cmp(rone) === 0 || x.cmp(rn1) === 0)
+      continue;
+
+    for (var i = 1; i < s; i++) {
+      x = x.redSqr();
+
+      if (x.cmp(rone) === 0)
+        return false;
+      if (x.cmp(rn1) === 0)
+        break;
+    }
+
+    if (i === s)
+      return false;
+  }
+
+  return prime;
+};
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..3e7417a
--- /dev/null
+++ b/package.json
@@ -0,0 +1,34 @@
+{
+  "name": "miller-rabin",
+  "version": "1.0.0",
+  "description": "Miller Rabin algorithm for primality test",
+  "main": "lib/mr.js",
+  "scripts": {
+    "test": "mocha --reporter=spec test/**/*-test.js"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git at github.com:indutny/miller-rabin"
+  },
+  "keywords": [
+    "prime",
+    "miller-rabin",
+    "bignumber"
+  ],
+  "author": "Fedor Indutny <fedor at indutny.com>",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/indutny/miller-rabin/issues"
+  },
+  "homepage": "https://github.com/indutny/miller-rabin",
+  "devDependencies": {
+    "bn.js": "^0.15.0",
+    "mocha": "^2.0.1"
+  },
+  "peerDependencies": {
+    "bn.js": "^0.15.0"
+  },
+  "dependencies": {
+    "brorand": "^1.0.1"
+  }
+}
diff --git a/test/api-test.js b/test/api-test.js
new file mode 100644
index 0000000..476a9ef
--- /dev/null
+++ b/test/api-test.js
@@ -0,0 +1,19 @@
+var assert = require('assert');
+var mr = require('../');
+var bn = require('bn.js');
+
+describe('Miller-Rabin', function() {
+  it('should test number for primality', function() {
+    assert(!mr.test(new bn(221)));
+    assert(mr.test(new bn(257)));
+
+    var p = new bn('dba8191813fe8f51eaae1de70213aafede8f323f95f32cff' +
+                   '8b64ebada275cfb18a446a0150e5fdaee246244c5f002ce0' +
+                   'aca97584be1745f2dd1eea2849c52aac8c4b5fb78a1c4da7' +
+                   '052774338d3310a6e020c46168cb1f94014e9312511cc4fb' +
+                   '79d695bb732449f0e015745b86bfa371dc6ca7386e9c7309' +
+                   '5549c2e4b8002873', 16);
+    assert(mr.test(p));
+    assert(!mr.test(p.subn(1)));
+  });
+});

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