OP-01-024 Random Range Bias in DSA/Elgamal (Low). Fix ranges, add TWO constant to BigInteger.

Thomas Oberndörfer · Thomas Oberndörfer · commit 3f626f4bfb23 · 2014-03-21T17:12:02.000+01:00
diff --git a/src/crypto/public_key/dsa.js b/src/crypto/public_key/dsa.js
@@ -49,7 +49,7 @@ function DSA() {
     // or s = 0 if signatures are generated properly.
     var k, s1, s2;
     while (true) {
-      k = random.getRandomBigIntegerInRange(BigInteger.ONE.add(BigInteger.ONE), q.subtract(BigInteger.ONE));
+      k = random.getRandomBigIntegerInRange(BigInteger.ONE, q.subtract(BigInteger.ONE));
       s1 = (g.modPow(k, p)).mod(q);
       s2 = (k.modInverse(q).multiply(hash.add(x.multiply(s1)))).mod(q);
       if (s1 != 0 && s2 != 0) {
diff --git a/src/crypto/public_key/elgamal.js b/src/crypto/public_key/elgamal.js
@@ -32,9 +32,8 @@ function Elgamal() {
 
   function encrypt(m, g, p, y) {
     //  choose k in {2,...,p-2}
-    var two = BigInteger.ONE.add(BigInteger.ONE);
-    var pMinus2 = p.subtract(two);
-    var k = random.getRandomBigIntegerInRange(two, pMinus2);
+    var pMinus2 = p.subtract(BigInteger.TWO);
+    var k = random.getRandomBigIntegerInRange(BigInteger.ONE, pMinus2);
     k = k.mod(pMinus2).add(BigInteger.ONE);
     var c = [];
     c[0] = g.modPow(k, p);
diff --git a/src/crypto/public_key/jsbn.js b/src/crypto/public_key/jsbn.js
@@ -730,6 +730,7 @@ BigInteger.prototype.modPowInt = bnModPowInt;
 // "constants"
 BigInteger.ZERO = nbv(0);
 BigInteger.ONE = nbv(1);
+BigInteger.TWO = nbv(2);
 
 module.exports = BigInteger;
 
diff --git a/src/crypto/public_key/rsa.js b/src/crypto/public_key/rsa.js
@@ -40,13 +40,12 @@ function SecureRandom() {
 
 var blinder = BigInteger.ZERO;
 var unblinder = BigInteger.ZERO;
-var TWO = BigInteger.ONE.add(BigInteger.ONE);
 
 function blind(m, n, e) {
   if (unblinder.bitLength() === n.bitLength()) {
     unblinder = unblinder.square().mod(n);
   } else {
-    unblinder = random.getRandomBigIntegerInRange(TWO, n);
+    unblinder = random.getRandomBigIntegerInRange(BigInteger.TWO, n);
   }
   blinder = unblinder.modInverse(n).modPow(e, n);
   return m.multiply(blinder).mod(n);
