[Pkg-javascript-commits] [node-diffie-hellman] 11/88: add prime generation

[Bastien Roucariès]

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rouca pushed a commit to branch master
in repository node-diffie-hellman.

commit feb843bb68872e2b2387839c10d0ecfa66476662
Author: Calvin Metcalf <cmetcalf at appgeo.com>
Date:   Wed Nov 5 07:11:22 2014 -0500

    add prime generation
---
 generatePrime.js | 138 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 138 insertions(+)

diff --git a/generatePrime.js b/generatePrime.js
new file mode 100644
index 0000000..368eeef
--- /dev/null
+++ b/generatePrime.js
@@ -0,0 +1,138 @@
+module.exports = generatePrime;
+
+var goodPrimes = {
+  256: 'k256',
+  224: 'p224',
+  192: 'p192',
+  25519: 'p25519'
+};
+function generatePrime(len, crypto) {
+  if (len in goodPrimes) {
+    return goodPrimes[len];
+  } else { 
+    return findPrime(len, crypto);
+  }
+}
+
+// based on find-prime by Kenan Yildirim
+// https://github.com/KenanY/find-prime
+
+//and
+//bigi https://github.com/cryptocoinjs/bigi
+//which is based on jsbn by Tom Wu
+//http://www-cs-students.stanford.edu/~tjw/jsbn/
+var BN = require('bn.js');
+var GCD_30_DELTA = [new BN(6), new BN(4), new BN(2), new BN(4), new BN(2), new BN(4), new BN(6), new BN(2)];
+
+
+function getMillerRabinTests(bits) {
+  if (bits <= 100) return 27;
+  if (bits <= 150) return 18;
+  if (bits <= 200) return 15;
+  if (bits <= 250) return 12;
+  if (bits <= 300) return 9;
+  if (bits <= 350) return 8;
+  if (bits <= 400) return 7;
+  if (bits <= 500) return 6;
+  if (bits <= 600) return 5;
+  if (bits <= 800) return 4;
+  if (bits <= 1250) return 3;
+  return 2;
+}
+var lowprimes = [
+  2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71,
+  73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151,
+  157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233,
+  239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317,
+  331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419,
+  421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503,
+  509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607,
+  613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701,
+  709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811,
+  821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911,
+  919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997
+];
+
+var lplim = (1 << 26) / lowprimes[lowprimes.length - 1];
+
+// (public) test primality with certainty >= 1-.5^t
+function isProbablePrime(n, t) {
+  var i, x = n.abs();
+  if (x.isEven()) return false;
+  i = 1;
+  while (i < lowprimes.length) {
+    var m = lowprimes[i],
+      j = i + 1;
+    while (j < lowprimes.length && m < lplim) m *= lowprimes[j++];
+    m = x.modn(m);
+    while (i < j) if (m % lowprimes[i++] === 0) return false;
+  }
+  return millerRabin(x, t);
+}
+function getLowestSetBit(n) {
+  var i = -1;
+  var len = n.bitLength();
+  while (++i < len) {
+    if (n.testn(i)) {
+      return i;
+    }
+  }
+  return -1;
+}
+// (protected) true if probably prime (HAC 4.24, Miller-Rabin)
+function millerRabin(n, t) {
+  var n1 = n.sub(new BN(1));
+  var mp = BN.mont(n);
+  var k = getLowestSetBit(n1);
+  if (k <= 0) return false;
+  var r = n1.shrn(k);
+  t = (t + 1) >> 1;
+  if (t > lowprimes.length) t = lowprimes.length;
+  var a;
+  var j, bases = []
+  for (var i = 0; i < t; ++i) {
+    for (;;) {
+      j = lowprimes[Math.floor(Math.random() * lowprimes.length)]
+      if (bases.indexOf(j) == -1) break;
+    }
+    bases.push(j);
+    a = new BN(j);
+    var y = a.toRed(mp).redPow(r).fromRed();
+    if (y.cmp(new BN(1)) != 0 && y.cmp(n1) != 0) {
+      var j = 1
+      while (j++ < k && y.cmp(n1) != 0) {
+        y = y.toRed(mp).redPow(new BN(2)).fromRed();
+        if (y.cmp(new BN(1)) == 0) return false
+      }
+      if (y.cmp(n1) != 0) return false
+    }
+  }
+  return true
+}
+function findPrime(bits, crypto) {
+
+  function generateRandom(bits) {
+    var bytes = bits >> 3;
+    bytes = bytes || 1;
+    return new BN(crypto.randomBytes(bits/8));
+  }
+  var num = generateRandom(bits);
+
+  var deltaIdx = 0;
+
+  var mrTests = getMillerRabinTests(num.bitLength());
+
+
+  while (true) {
+    if (num.bitLength() > bits) {
+      num = generateRandom(bits);
+    }
+
+    if(isProbablePrime(num, mrTests)) {
+      return num;
+    }
+
+    num.iadd(GCD_30_DELTA[deltaIdx++ % 8]);
+  }
+
+}
\ No newline at end of file

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