diff --git a/lib/bcoin/siphash.js b/lib/bcoin/siphash.js
new file mode 100644
index 00000000..27cc84bf
--- /dev/null
+++ b/lib/bcoin/siphash.js
@@ -0,0 +1,184 @@
+/*!
+ * siphash.js - siphash for bcoin
+ * Copyright (c) 2016, Christopher Jeffrey (MIT License).
+ * https://github.com/indutny/bcoin
+ *
+ * Ported from:
+ * https://github.com/bitcoin/bitcoin/blob/master/src/hash.cpp
+ */
+
+/**
+ * Javascript siphash implementation. Used for compact block relay.
+ * @param {Buffer} data - Blocks are uint64le's.
+ * @param {Buffer} k0 - Must be encoded as a uint64le.
+ * @param {Buffer} k1 - Must be encoded as a uint64le.
+ * @returns {Buffer} uint64le
+ */
+
+function siphash(data, k0, k1) {
+  var out = new Buffer(8);
+  var blocks = Math.ceil(data.length / 8);
+  var c0 = { hi: 0x736f6d65, lo: 0x70736575 };
+  var c1 = { hi: 0x646f7261, lo: 0x6e646f6d };
+  var c2 = { hi: 0x6c796765, lo: 0x6e657261 };
+  var c3 = { hi: 0x74656462, lo: 0x79746573 };
+  var f0 = { hi: blocks << 27, lo: 0 };
+  var f1 = { hi: 0, lo: 0xff };
+  var i, d, v0, v1, v2, v3;
+
+  k0 = read(k0, 0);
+  k1 = read(k1, 0);
+
+  // Init
+  v0 = xor64(c0, k0);
+  v1 = xor64(c1, k1);
+  v2 = xor64(c2, k0);
+  v3 = xor64(c3, k1);
+
+  // Blocks
+  for (i = 0; i < blocks; i++) {
+    d = read(data, i * 8);
+    xor64(v3, d);
+    sipround(v0, v1, v2, v3);
+    sipround(v0, v1, v2, v3);
+    xor64(v0, d);
+  }
+
+  // Finalization
+  xor64(v3, f0);
+  sipround(v0, v1, v2, v3);
+  sipround(v0, v1, v2, v3);
+  xor64(v0, f0);
+  xor64(v2, f1);
+  sipround(v0, v1, v2, v3);
+  sipround(v0, v1, v2, v3);
+  sipround(v0, v1, v2, v3);
+  sipround(v0, v1, v2, v3);
+  xor64(v0, v1);
+  xor64(v0, v2);
+  xor64(v0, v3);
+
+  write(out, v0, 0);
+
+  return out;
+}
+
+function sipround(v0, v1, v2, v3) {
+  sum64(v0, v1);
+  rotl64(v1, 13);
+  xor64(v1, v0);
+
+  rotl64(v0, 32);
+
+  sum64(v2, v3);
+  rotl64(v3, 16);
+  xor64(v3, v2);
+
+  sum64(v0, v3);
+  rotl64(v3, 21);
+  xor64(v3, v0);
+
+  sum64(v2, v1);
+  rotl64(v1, 17);
+  xor64(v1, v2);
+
+  rotl64(v2, 32);
+}
+
+/*
+ * Helpers
+ */
+
+function sum64(a, b) {
+  var r, carry;
+
+  r = a.lo + b.lo;
+  carry = (r - (r % 0x100000000)) / 0x100000000;
+  a.hi = (a.hi + b.hi + carry) & 0xffffffff;
+  a.lo = r & 0xffffffff;
+
+  if (a.hi < 0)
+    a.hi += 0x100000000;
+
+  if (a.lo < 0)
+    a.lo += 0x100000000;
+
+  return a;
+}
+
+function rotl64(x, b) {
+  var hi, lo, h1, l1, h2, l2, c;
+
+  // v1 = x << b
+  if (b < 32) {
+    h1 = x.hi << b;
+    c = x.lo >>> (32 - b);
+    l1 = x.lo << b;
+    h1 |= c;
+  } else {
+    h1 = x.lo << (b - 32);
+    l1 = 0;
+  }
+
+  // v2 = x >> (64 - b)
+  b = 64 - b;
+  if (b < 32) {
+    h2 = x.hi >>> b;
+    c = x.hi & (0xffffffff >>> (32 - b));
+    l2 = x.lo >>> b;
+    l2 |= c << (32 - b);
+  } else {
+    h2 = 0;
+    l2 = x.hi >>> (b - 32);
+  }
+
+  // v1 | v2
+  hi = h1 | h2;
+  lo = l1 | l2;
+
+  x.hi = hi;
+  x.lo = lo;
+
+  if (x.hi < 0)
+    x.hi += 0x100000000;
+
+  if (x.lo < 0)
+    x.lo += 0x100000000;
+
+  return x;
+}
+
+function xor64(a, b) {
+  a.hi ^= b.hi;
+  a.lo ^= b.lo;
+
+  if (a.hi < 0)
+    a.hi += 0x100000000;
+
+  if (a.lo < 0)
+    a.lo += 0x100000000;
+
+  return a;
+}
+
+function read(data, off) {
+  return {
+    hi: data.readUInt32LE(off + 4, true),
+    lo: data.readUInt32LE(off, true)
+  };
+}
+
+function write(data, value, off) {
+  data.writeUInt32LE(value.hi, off + 4, true);
+  data.writeUInt32LE(value.lo, off, true);
+}
+
+/*
+ * Expose
+ */
+
+exports = siphash;
+exports.write = write;
+exports.read = read;
+
+module.exports = exports;
diff --git a/test/siphash-test.js b/test/siphash-test.js
new file mode 100644
index 00000000..623792c3
--- /dev/null
+++ b/test/siphash-test.js
@@ -0,0 +1,40 @@
+var assert = require('assert');
+var siphash = require('../lib/bcoin/siphash');
+
+describe('SipHash', function() {
+  it('should perform siphash with no data', function() {
+    var k0 = new Buffer(8);
+    var k1 = new Buffer(8);
+    siphash.write(k0, { hi: 0x07060504, lo: 0x03020100 }, 0);
+    siphash.write(k1, { hi: 0x0F0E0D0C, lo: 0x0B0A0908 }, 0);
+    // be:
+    // assert.equal(siphash(k0, k1, new Buffer(0)).toString('hex'), '726fdb47dd0e0e31');
+    // le:
+    assert.equal(siphash(new Buffer(0), k0, k1).toString('hex'), '310e0edd47db6f72');
+  });
+
+  it('should perform siphash with data', function() {
+    var k0 = new Buffer(8);
+    var k1 = new Buffer(8);
+    var data = new Buffer(8);
+    siphash.write(k0, { hi: 0x07060504, lo: 0x03020100 }, 0);
+    siphash.write(k1, { hi: 0x0F0E0D0C, lo: 0x0B0A0908 }, 0);
+    siphash.write(data, { hi: 0x07060504, lo: 0x03020100 }, 0);
+    // be:
+    // assert.equal(siphash(k0, k1, data).toString('hex'), '93f5f5799a932462');
+    // le:
+    assert.equal(siphash(data, k0, k1).toString('hex'), '6224939a79f5f593');
+  });
+
+  it('should perform siphash with uint256', function() {
+    var k0 = new Buffer(8);
+    var k1 = new Buffer(8);
+    siphash.write(k0, { hi: 0x07060504, lo: 0x03020100 }, 0);
+    siphash.write(k1, { hi: 0x0F0E0D0C, lo: 0x0B0A0908 }, 0);
+    var hash = new Buffer('000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f', 'hex');
+    // be:
+    // assert.equal(siphash(k0, k1, hash).toString('hex'), '7127512f72f27cce');
+    // le:
+    assert.equal(siphash(hash, k0, k1).toString('hex'), 'ce7cf2722f512771');
+  });
+});