diff --git a/lib/elliptic/ec/key.js b/lib/elliptic/ec/key.js
index 8d075fb3..69054b3e 100644
--- a/lib/elliptic/ec/key.js
+++ b/lib/elliptic/ec/key.js
@@ -89,6 +89,9 @@ KeyPair.prototype._importPublic = function _importPublic(key, enc) {
 
 // ECDH
 KeyPair.prototype.derive = function derive(pub) {
+  if(!pub.validate()) {
+    assert(pub.validate(), 'public point not validated');
+  }
   return pub.mul(this.priv).getX();
 };
 
diff --git a/lib/elliptic/ec/key.js.orig b/lib/elliptic/ec/key.js.orig
new file mode 100644
index 00000000..8d075fb3
--- /dev/null
+++ b/lib/elliptic/ec/key.js.orig
@@ -0,0 +1,107 @@
+'use strict';
+
+var BN = require('bn.js');
+
+function KeyPair(ec, options) {
+  this.ec = ec;
+  this.priv = null;
+  this.pub = null;
+
+  // KeyPair(ec, { priv: ..., pub: ... })
+  if (options.priv)
+    this._importPrivate(options.priv, options.privEnc);
+  if (options.pub)
+    this._importPublic(options.pub, options.pubEnc);
+}
+module.exports = KeyPair;
+
+KeyPair.fromPublic = function fromPublic(ec, pub, enc) {
+  if (pub instanceof KeyPair)
+    return pub;
+
+  return new KeyPair(ec, {
+    pub: pub,
+    pubEnc: enc
+  });
+};
+
+KeyPair.fromPrivate = function fromPrivate(ec, priv, enc) {
+  if (priv instanceof KeyPair)
+    return priv;
+
+  return new KeyPair(ec, {
+    priv: priv,
+    privEnc: enc
+  });
+};
+
+KeyPair.prototype.validate = function validate() {
+  var pub = this.getPublic();
+
+  if (pub.isInfinity())
+    return { result: false, reason: 'Invalid public key' };
+  if (!pub.validate())
+    return { result: false, reason: 'Public key is not a point' };
+  if (!pub.mul(this.ec.curve.n).isInfinity())
+    return { result: false, reason: 'Public key * N != O' };
+
+  return { result: true, reason: null };
+};
+
+KeyPair.prototype.getPublic = function getPublic(compact, enc) {
+  // compact is optional argument
+  if (typeof compact === 'string') {
+    enc = compact;
+    compact = null;
+  }
+
+  if (!this.pub)
+    this.pub = this.ec.g.mul(this.priv);
+
+  if (!enc)
+    return this.pub;
+
+  return this.pub.encode(enc, compact);
+};
+
+KeyPair.prototype.getPrivate = function getPrivate(enc) {
+  if (enc === 'hex')
+    return this.priv.toString(16, 2);
+  else
+    return this.priv;
+};
+
+KeyPair.prototype._importPrivate = function _importPrivate(key, enc) {
+  this.priv = new BN(key, enc || 16);
+
+  // Ensure that the priv won't be bigger than n, otherwise we may fail
+  // in fixed multiplication method
+  this.priv = this.priv.umod(this.ec.curve.n);
+};
+
+KeyPair.prototype._importPublic = function _importPublic(key, enc) {
+  if (key.x || key.y) {
+    this.pub = this.ec.curve.point(key.x, key.y);
+    return;
+  }
+  this.pub = this.ec.curve.decodePoint(key, enc);
+};
+
+// ECDH
+KeyPair.prototype.derive = function derive(pub) {
+  return pub.mul(this.priv).getX();
+};
+
+// ECDSA
+KeyPair.prototype.sign = function sign(msg, enc, options) {
+  return this.ec.sign(msg, this, enc, options);
+};
+
+KeyPair.prototype.verify = function verify(msg, signature) {
+  return this.ec.verify(msg, signature, this);
+};
+
+KeyPair.prototype.inspect = function inspect() {
+  return '<Key priv: ' + (this.priv && this.priv.toString(16, 2)) +
+         ' pub: ' + (this.pub && this.pub.inspect()) + ' >';
+};
diff --git a/lib/elliptic/ec/signature.js b/lib/elliptic/ec/signature.js
index 165b179a..85c63701 100644
--- a/lib/elliptic/ec/signature.js
+++ b/lib/elliptic/ec/signature.js
@@ -33,11 +33,24 @@ function getLength(buf, p) {
     return initial;
   }
   var octetLen = initial & 0xf;
+
+  // Indefinite length or overflow
+  if (octetLen === 0 || octetLen > 4) {
+    return false;
+  }
+
   var val = 0;
   for (var i = 0, off = p.place; i < octetLen; i++, off++) {
     val <<= 8;
     val |= buf[off];
+    val >>>= 0;
   }
+
+  // Leading zeroes
+  if (val <= 0x7f) {
+    return false;
+  }
+
   p.place = off;
   return val;
 }
@@ -61,6 +74,9 @@ Signature.prototype._importDER = function _importDER(data, enc) {
     return false;
   }
   var len = getLength(data, p);
+  if (len === false) {
+    return false;
+  }
   if ((len + p.place) !== data.length) {
     return false;
   }
@@ -68,21 +84,37 @@ Signature.prototype._importDER = function _importDER(data, enc) {
     return false;
   }
   var rlen = getLength(data, p);
+  if (rlen === false) {
+    return false;
+  }
   var r = data.slice(p.place, rlen + p.place);
   p.place += rlen;
   if (data[p.place++] !== 0x02) {
     return false;
   }
   var slen = getLength(data, p);
+  if (slen === false) {
+    return false;
+  }
   if (data.length !== slen + p.place) {
     return false;
   }
   var s = data.slice(p.place, slen + p.place);
-  if (r[0] === 0 && (r[1] & 0x80)) {
-    r = r.slice(1);
+  if (r[0] === 0) {
+    if (r[1] & 0x80) {
+      r = r.slice(1);
+    } else {
+      // Leading zeroes
+      return false;
+    }
   }
-  if (s[0] === 0 && (s[1] & 0x80)) {
-    s = s.slice(1);
+  if (s[0] === 0) {
+    if (s[1] & 0x80) {
+      s = s.slice(1);
+    } else {
+      // Leading zeroes
+      return false;
+    }
   }
 
   this.r = new BN(r);
diff --git a/lib/elliptic/ec/signature.js.orig b/lib/elliptic/ec/signature.js.orig
new file mode 100644
index 00000000..165b179a
--- /dev/null
+++ b/lib/elliptic/ec/signature.js.orig
@@ -0,0 +1,135 @@
+'use strict';
+
+var BN = require('bn.js');
+
+var elliptic = require('../../elliptic');
+var utils = elliptic.utils;
+var assert = utils.assert;
+
+function Signature(options, enc) {
+  if (options instanceof Signature)
+    return options;
+
+  if (this._importDER(options, enc))
+    return;
+
+  assert(options.r && options.s, 'Signature without r or s');
+  this.r = new BN(options.r, 16);
+  this.s = new BN(options.s, 16);
+  if (options.recoveryParam === undefined)
+    this.recoveryParam = null;
+  else
+    this.recoveryParam = options.recoveryParam;
+}
+module.exports = Signature;
+
+function Position() {
+  this.place = 0;
+}
+
+function getLength(buf, p) {
+  var initial = buf[p.place++];
+  if (!(initial & 0x80)) {
+    return initial;
+  }
+  var octetLen = initial & 0xf;
+  var val = 0;
+  for (var i = 0, off = p.place; i < octetLen; i++, off++) {
+    val <<= 8;
+    val |= buf[off];
+  }
+  p.place = off;
+  return val;
+}
+
+function rmPadding(buf) {
+  var i = 0;
+  var len = buf.length - 1;
+  while (!buf[i] && !(buf[i + 1] & 0x80) && i < len) {
+    i++;
+  }
+  if (i === 0) {
+    return buf;
+  }
+  return buf.slice(i);
+}
+
+Signature.prototype._importDER = function _importDER(data, enc) {
+  data = utils.toArray(data, enc);
+  var p = new Position();
+  if (data[p.place++] !== 0x30) {
+    return false;
+  }
+  var len = getLength(data, p);
+  if ((len + p.place) !== data.length) {
+    return false;
+  }
+  if (data[p.place++] !== 0x02) {
+    return false;
+  }
+  var rlen = getLength(data, p);
+  var r = data.slice(p.place, rlen + p.place);
+  p.place += rlen;
+  if (data[p.place++] !== 0x02) {
+    return false;
+  }
+  var slen = getLength(data, p);
+  if (data.length !== slen + p.place) {
+    return false;
+  }
+  var s = data.slice(p.place, slen + p.place);
+  if (r[0] === 0 && (r[1] & 0x80)) {
+    r = r.slice(1);
+  }
+  if (s[0] === 0 && (s[1] & 0x80)) {
+    s = s.slice(1);
+  }
+
+  this.r = new BN(r);
+  this.s = new BN(s);
+  this.recoveryParam = null;
+
+  return true;
+};
+
+function constructLength(arr, len) {
+  if (len < 0x80) {
+    arr.push(len);
+    return;
+  }
+  var octets = 1 + (Math.log(len) / Math.LN2 >>> 3);
+  arr.push(octets | 0x80);
+  while (--octets) {
+    arr.push((len >>> (octets << 3)) & 0xff);
+  }
+  arr.push(len);
+}
+
+Signature.prototype.toDER = function toDER(enc) {
+  var r = this.r.toArray();
+  var s = this.s.toArray();
+
+  // Pad values
+  if (r[0] & 0x80)
+    r = [ 0 ].concat(r);
+  // Pad values
+  if (s[0] & 0x80)
+    s = [ 0 ].concat(s);
+
+  r = rmPadding(r);
+  s = rmPadding(s);
+
+  while (!s[0] && !(s[1] & 0x80)) {
+    s = s.slice(1);
+  }
+  var arr = [ 0x02 ];
+  constructLength(arr, r.length);
+  arr = arr.concat(r);
+  arr.push(0x02);
+  constructLength(arr, s.length);
+  var backHalf = arr.concat(s);
+  var res = [ 0x30 ];
+  constructLength(res, backHalf.length);
+  res = res.concat(backHalf);
+  return utils.encode(res, enc);
+};
diff --git a/test/ecdh-test.js b/test/ecdh-test.js
index 9f8f6f0d..4eb4fe3b 100644
--- a/test/ecdh-test.js
+++ b/test/ecdh-test.js
@@ -25,3 +25,17 @@ describe('ECDH', function() {
   test('ed25519');
   test('secp256k1');
 });
+
+describe('ECDH twist attack', () => {
+  it('should be able to prevent a twist attack for secp256k1', () => {
+    var bobEcdh = new elliptic.ec('secp256k1');
+    var malloryEcdh = new elliptic.ec('secp256k1');
+    var bob = bobEcdh.genKeyPair();
+    // This is a bad point that shouldn't be able to be passed to derive.
+    // If a bad point can be passed it's possible to perform a twist attack.
+    var mallory = malloryEcdh.keyFromPublic({ x: 14, y: 16 });
+    assert.throws(function () {
+      bob.derive(mallory.getPublic());
+    });
+  });
+});
diff --git a/test/ecdh-test.js.orig b/test/ecdh-test.js.orig
new file mode 100644
index 00000000..9f8f6f0d
--- /dev/null
+++ b/test/ecdh-test.js.orig
@@ -0,0 +1,27 @@
+var assert = require('assert');
+var elliptic = require('../');
+var hash = require('hash.js');
+
+describe('ECDH', function() {
+  function test(name) {
+    it('should work with ' + name + ' curve', function() {
+      var ecdh = new elliptic.ec(name);
+      var s1 = ecdh.genKeyPair();
+      var s2 = ecdh.genKeyPair();
+      var sh1 = s1.derive(s2.getPublic());
+      var sh2 = s2.derive(s1.getPublic());
+
+      assert.equal(sh1.toString(16), sh2.toString(16));
+
+      var sh1 = s1.derive(ecdh.keyFromPublic(s2.getPublic('hex'), 'hex')
+                              .getPublic());
+      var sh2 = s2.derive(ecdh.keyFromPublic(s1.getPublic('hex'), 'hex')
+                              .getPublic());
+      assert.equal(sh1.toString(16), sh2.toString(16));
+    });
+  }
+
+  test('curve25519');
+  test('ed25519');
+  test('secp256k1');
+});