diff --git a/lib/utils/gcs.js b/lib/utils/gcs.js
index 9dc0e873..69faf19d 100644
--- a/lib/utils/gcs.js
+++ b/lib/utils/gcs.js
@@ -12,6 +12,7 @@ var crypto = require('../crypto/crypto');
 var siphash24 = require('../crypto/siphash');
 var SCRATCH = Buffer.allocUnsafe(64);
 var DUMMY = Buffer.allocUnsafe(0);
+var EOF = new Int64(-1);
 
 /**
  * GCSFilter
@@ -21,7 +22,7 @@ var DUMMY = Buffer.allocUnsafe(0);
 function GCSFilter() {
   this.n = 0;
   this.p = 0;
-  this.m = Int64(0);
+  this.m = new Int64(0);
   this.data = DUMMY;
 }
 
@@ -41,17 +42,14 @@ GCSFilter.prototype.header = function header(prev) {
 GCSFilter.prototype.match = function match(key, data) {
   var br = new BitReader(this.data);
   var term = siphash(data, key).imod(this.m);
-  var last = Int64(0);
+  var last = new Int64(0);
   var value;
 
   while (last.lt(term)) {
-    try {
-      value = this.readU64(br);
-    } catch (e) {
-      if (e.message === 'EOF')
-        return false;
-      throw e;
-    }
+    value = this.readU64(br);
+
+    if (value === EOF)
+      return false;
 
     value.iadd(last);
 
@@ -66,7 +64,7 @@ GCSFilter.prototype.match = function match(key, data) {
 
 GCSFilter.prototype.matchAny = function matchAny(key, items) {
   var br = new BitReader(this.data);
-  var last1 = Int64(0);
+  var last1 = new Int64(0);
   var values = [];
   var i, item, hash, last2, cmp, value;
 
@@ -98,13 +96,10 @@ GCSFilter.prototype.matchAny = function matchAny(key, items) {
       return false;
     }
 
-    try {
-      value = this.readU64(br);
-    } catch (e) {
-      if (e.message === 'EOF')
-        return false;
-      throw e;
-    }
+    value = this.readU64(br);
+
+    if (value === EOF)
+      return false;
 
     last1.iadd(value);
   }
@@ -113,18 +108,26 @@ GCSFilter.prototype.matchAny = function matchAny(key, items) {
 };
 
 GCSFilter.prototype.readU64 = function readU64(br) {
-  var num = Int64(0);
-  var bit = br.readBit();
+  try {
+    return this._readU64(br);
+  } catch (e) {
+    if (e.message === 'EOF')
+      return EOF;
+    throw e;
+  }
+};
+
+GCSFilter.prototype._readU64 = function _readU64(br) {
+  var num = new Int64(0);
   var rem;
 
-  while (bit) {
+  // Unary
+  while (br.readBit())
     num.iaddn(1);
-    bit = br.readBit();
-  }
 
   rem = br.readBits64(this.p);
 
-  return num.ishln(this.p).iadd(rem);
+  return num.ishln(this.p).ior(rem);
 };
 
 GCSFilter.prototype.toBytes = function toBytes() {
@@ -153,10 +156,16 @@ GCSFilter.prototype.toNPBytes = function toNPBytes() {
   return data;
 };
 
+GCSFilter.prototype.toRaw = function toRaw() {
+  assert(this.p === 20);
+  return this.toNBytes();
+};
+
 GCSFilter.prototype.fromItems = function fromItems(P, key, items) {
+  var bw = new BitWriter();
+  var last = new Int64(0);
   var values = [];
-  var last = Int64(0);
-  var i, bw, item, hash, value, rem;
+  var i, item, hash, value, rem;
 
   assert(typeof P === 'number' && isFinite(P));
   assert(P >= 0 && P <= 32);
@@ -172,8 +181,6 @@ GCSFilter.prototype.fromItems = function fromItems(P, key, items) {
   this.p = P;
   this.m = Int64(this.n).ishln(this.p);
 
-  bw = new BitWriter();
-
   for (i = 0; i < items.length; i++) {
     item = items[i];
     assert(Buffer.isBuffer(item));
@@ -254,6 +261,10 @@ GCSFilter.prototype.fromNPBytes = function fromNPBytes(data) {
   return this.fromBytes(N, P, data.slice(5));
 };
 
+GCSFilter.prototype.fromRaw = function fromRaw(data) {
+  return this.fromNBytes(20, data);
+};
+
 GCSFilter.prototype.fromBlock = function fromBlock(block) {
   var hash = block.hash();
   var key = hash.slice(0, 16);
@@ -322,6 +333,10 @@ GCSFilter.fromNPBytes = function fromNPBytes(data) {
   return new GCSFilter().fromNPBytes(data);
 };
 
+GCSFilter.fromRaw = function fromRaw(data) {
+  return new GCSFilter().fromRaw(data);
+};
+
 GCSFilter.fromBlock = function fromBlock(block) {
   return new GCSFilter().fromBlock(block);
 };
@@ -356,7 +371,7 @@ BitWriter.prototype.writeBit = function writeBit(bit) {
   this.remain--;
 };
 
-BitWriter.prototype.writeOneByte = function writeOneByte(ch) {
+BitWriter.prototype.writeByte = function writeByte(ch) {
   var index;
 
   if (this.remain === 0) {
@@ -366,9 +381,9 @@ BitWriter.prototype.writeOneByte = function writeOneByte(ch) {
 
   index = this.stream.length - 1;
 
-  this.stream[index] |= ch >> (8 - this.remain);
+  this.stream[index] |= (ch >> (8 - this.remain)) & 0xff;
   this.stream.push(0);
-  this.stream[index + 1] = ch << this.remain;
+  this.stream[index + 1] = (ch << this.remain) & 0xff;
 };
 
 BitWriter.prototype.writeBits = function writeBits(num, count) {
@@ -381,8 +396,7 @@ BitWriter.prototype.writeBits = function writeBits(num, count) {
 
   while (count >= 8) {
     ch = num >>> 24;
-    this.writeOneByte(ch);
-
+    this.writeByte(ch);
     num <<= 8;
     count -= 8;
   }
@@ -391,11 +405,14 @@ BitWriter.prototype.writeBits = function writeBits(num, count) {
     bit = num >>> 31;
     this.writeBit(bit);
     num <<= 1;
-    count--;
+    count -= 1;
   }
 };
 
 BitWriter.prototype.writeBits64 = function writeBits64(num, count) {
+  assert(count >= 0);
+  assert(count <= 64);
+
   if (count > 32) {
     this.writeBits(num.hi, count - 32);
     this.writeBits(num.lo, 32);
@@ -405,12 +422,11 @@ BitWriter.prototype.writeBits64 = function writeBits64(num, count) {
 };
 
 BitWriter.prototype.render = function render() {
-  var stream = this.stream;
-  var data = Buffer.allocUnsafe(stream.length);
+  var data = Buffer.allocUnsafe(this.stream.length);
   var i;
 
-  for (i = 0; i < stream.length; i++)
-    data[i] = stream[i];
+  for (i = 0; i < this.stream.length; i++)
+    data[i] = this.stream[i];
 
   return data;
 };
@@ -421,7 +437,7 @@ BitWriter.prototype.render = function render() {
  */
 
 function BitReader(data) {
-  this.stream = copy(data);
+  this.stream = data;
   this.pos = 0;
   this.remain = 8;
 }
@@ -441,13 +457,9 @@ BitReader.prototype.readBit = function readBit() {
     this.remain = 8;
   }
 
-  bit = this.stream[this.pos] & 0x80;
+  this.remain -= 1;
 
-  this.stream[this.pos] <<= 1;
-  this.stream[this.pos] &= 0xff;
-  this.remain--;
-
-  return bit !== 0 ? 1 : 0;
+  return (this.stream[this.pos] >> this.remain) & 1;
 };
 
 BitReader.prototype.readByte = function readByte() {
@@ -471,7 +483,9 @@ BitReader.prototype.readByte = function readByte() {
     return ch;
   }
 
-  ch = this.stream[this.pos];
+  ch = this.stream[this.pos] & ((1 << this.remain) - 1);
+  ch <<= 8 - this.remain;
+
   this.pos += 1;
 
   if (this.pos >= this.stream.length)
@@ -479,31 +493,24 @@ BitReader.prototype.readByte = function readByte() {
 
   ch |= this.stream[this.pos] >> this.remain;
 
-  this.stream[this.pos] <<= (8 - this.remain);
-  this.stream[this.pos] &= 0xff;
-
   return ch;
 };
 
 BitReader.prototype.readBits = function readBits(count) {
   var num = 0;
-  var ch, bit;
 
   assert(count >= 0);
   assert(count <= 32);
 
   while (count >= 8) {
     num <<= 8;
-    ch = this.readByte();
-    num |= ch;
+    num |= this.readByte();
     count -= 8;
   }
 
   while (count > 0) {
     num <<= 1;
-    bit = this.readBit();
-    if (bit)
-      num |= 1;
+    num |= this.readBit();
     count -= 1;
   }
 
@@ -511,16 +518,19 @@ BitReader.prototype.readBits = function readBits(count) {
 };
 
 BitReader.prototype.readBits64 = function readBits(count) {
-  var n = new Int64();
+  var num = new Int64();
+
+  assert(count >= 0);
+  assert(count <= 64);
 
   if (count > 32) {
-    n.hi = this.readBits(count - 32);
-    n.lo = this.readBits(32);
+    num.hi = this.readBits(count - 32);
+    num.lo = this.readBits(32);
   } else {
-    n.lo = this.readBits(count);
+    num.lo = this.readBits(count);
   }
 
-  return n;
+  return num;
 };
 
 /*
@@ -532,14 +542,11 @@ function compare(a, b) {
 }
 
 function siphash(data, key) {
+  var num = new Int64();
   var hash = siphash24(data, key);
-  return Int64().join(hash.hi, hash.lo);
-}
-
-function copy(data) {
-  var clone = Buffer.allocUnsafe(data.length);
-  data.copy(clone, 0, 0, data.length);
-  return clone;
+  num.hi = hash.hi | 0;
+  num.lo = hash.lo | 0;
+  return num;
 }
 
 function getPushes(items, script) {