diff --git a/lib/bcoin/address.js b/lib/bcoin/address.js
index 25e8b386..9fa164ad 100644
--- a/lib/bcoin/address.js
+++ b/lib/bcoin/address.js
@@ -312,7 +312,7 @@ Address.prototype.scriptInputs = function scriptInputs(tx, index) {
   return total;
 };
 
-Address.prototype.signInputs = function signInputs(tx, type, index) {
+Address.prototype.signInputs = function signInputs(tx, index, type) {
   var total = 0;
   var i, input;
 
@@ -341,7 +341,7 @@ Address.prototype.signInputs = function signInputs(tx, type, index) {
   return total;
 };
 
-Address.prototype.sign = function sign(tx, type, index) {
+Address.prototype.sign = function sign(tx, index, type) {
   var total = 0;
   var i, input;
 
diff --git a/lib/bcoin/chaindb.js b/lib/bcoin/chaindb.js
index af24453a..d151b0db 100644
--- a/lib/bcoin/chaindb.js
+++ b/lib/bcoin/chaindb.js
@@ -62,6 +62,7 @@ ChainDB.prototype._init = function _init() {
   this.db = bcoin.ldb({
     name: this.options.name || (this.options.spv ? 'spvchain' : 'chain'),
     location: this.options.location,
+    db: this.options.db,
     compression: true,
     cacheSize: 16 << 20,
     writeBufferSize: 8 << 20
diff --git a/lib/bcoin/input.js b/lib/bcoin/input.js
index eba9ce51..0366924b 100644
--- a/lib/bcoin/input.js
+++ b/lib/bcoin/input.js
@@ -25,14 +25,14 @@ function Input(options, tx) {
   this.witness = bcoin.script.witness(options.witness);
   this._mutable = !tx || (tx instanceof bcoin.mtx);
 
-  if (options.coin) {
+  if (options.coin)
     this.coin = bcoin.coin(options.coin);
-    assert(typeof this.coin.hash === 'string');
-    assert(typeof this.coin.index === 'number');
-  }
 
   if (Buffer.isBuffer(this.prevout.hash))
     this.prevout.hash = utils.toHex(this.prevout.hash);
+
+  assert(typeof this.prevout.hash === 'string');
+  assert(typeof this.prevout.index === 'number');
 }
 
 Input.prototype.__defineGetter__('type', function() {
diff --git a/lib/bcoin/mempool.js b/lib/bcoin/mempool.js
index a4bb911c..193c4b7f 100644
--- a/lib/bcoin/mempool.js
+++ b/lib/bcoin/mempool.js
@@ -87,7 +87,7 @@ Mempool.prototype._init = function _init() {
   var options = {
     name: this.options.name || 'mempool',
     location: this.options.location,
-    db: this.backend
+    db: this.options.db || this.backend
   };
 
   assert(unlock);
diff --git a/lib/bcoin/mtx.js b/lib/bcoin/mtx.js
index 5c7602d0..e4035d79 100644
--- a/lib/bcoin/mtx.js
+++ b/lib/bcoin/mtx.js
@@ -164,7 +164,7 @@ MTX.prototype.scriptInput = function scriptInput(index, addr) {
   assert(input);
 
   // We should have previous outputs by now.
-  assert(input.coin);
+  assert(input.coin, 'Coins are not available for scripting.');
 
   // Optimization: Don't bother with any below
   // calculation if the output is already templated.
@@ -348,7 +348,7 @@ MTX.prototype.signInput = function signInput(index, addr, type) {
   assert(input);
 
   // We should have previous outputs by now.
-  assert(input.coin);
+  assert(input.coin, 'Coins are not available for signing.');
 
   // Get the previous output's script
   prev = input.coin.script;
diff --git a/lib/bcoin/reader.js b/lib/bcoin/reader.js
index 34e7f8f9..7572bbe1 100644
--- a/lib/bcoin/reader.js
+++ b/lib/bcoin/reader.js
@@ -284,8 +284,6 @@ BufferReader.prototype.seek = function seek(off) {
 };
 
 BufferReader.prototype.createChecksum = function createChecksum() {
-  assert(this.offset + 4 >= 0);
-  assert(this.offset + 4 <= this.data.length);
   var start = this.stack[this.stack.length - 1] || 0;
   var data = this.data.slice(start, this.offset);
   return utils.readU32BE(utils.checksum(data), 0);
diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index 526362ee..cd066b3e 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -1012,7 +1012,7 @@ utils.read64BE = function read64BE(arr, off) {
     return new bn(num, 'be').notn(64).addn(1).neg();
   }
 
-  return new bn(num);
+  return new bn(num, 'be');
 };
 
 utils.writeU8 = function writeU8(dst, num, off) {
@@ -1436,10 +1436,10 @@ utils.cmp = function cmp(a, b) {
   }
 
   if (a.length < b.length)
-    return  -1;
+    return -1;
 
   if (a.length > b.length)
-    return  1;
+    return 1;
 
   return 0;
 };
@@ -1756,7 +1756,7 @@ utils.indexOf = function indexOf(arr, buf) {
 };
 
 utils.pad32 = function pad32(num) {
-  assert(num >= 0, num);
+  assert(num >= 0);
   num = num + '';
   while (num.length < 10)
     num = '0' + num;
diff --git a/lib/bcoin/wallet.js b/lib/bcoin/wallet.js
index 59b9fe2c..f9e8aa71 100644
--- a/lib/bcoin/wallet.js
+++ b/lib/bcoin/wallet.js
@@ -10,6 +10,7 @@ var utils = require('./utils');
 var assert = utils.assert;
 var constants = bcoin.protocol.constants;
 var network = bcoin.protocol.network;
+var BufferWriter = require('./writer');
 
 /**
  * Wallet
@@ -66,7 +67,8 @@ function Wallet(options) {
   if (this.n > 1)
     this.type = 'multisig';
 
-  assert(this.type === 'pubkeyhash' || this.type === 'multisig');
+  assert(this.type === 'pubkeyhash' || this.type === 'multisig',
+    '`type` must be multisig or pubkeyhash.');
 
   if (this.m < 1 || this.m > this.n)
     throw new Error('m ranges between 1 and n');
@@ -84,8 +86,7 @@ function Wallet(options) {
   this.id = this.getID();
 
   // Non-alphanumeric IDs will break leveldb sorting.
-  if (!/^[a-zA-Z0-9]+$/.test(this.id))
-    throw new Error('Wallet IDs must be alphanumeric.');
+  assert(/^[a-zA-Z0-9]+$/.test(this.id), 'Wallet IDs must be alphanumeric.');
 
   this.addKey(this.accountKey);
 
@@ -296,17 +297,19 @@ Wallet.prototype._finalizeKeys = function _finalizeKeys() {
 // bip44: Account key "address" (prefix: WLT)
 Wallet.prototype.getID = function getID() {
   var publicKey = this.accountKey.publicKey;
-  var id;
+  var p;
 
   if (this.options.id)
     return this.options.id;
 
-  id = new Buffer(27);
-  utils.copy(new Buffer([0x03, 0xbe, 0x04]), id, 0);
-  utils.copy(utils.ripesha(publicKey), id, 3);
-  utils.copy(utils.checksum(id.slice(0, 23)), id, 23);
+  p = new BufferWriter();
+  p.writeU8(0x03);
+  p.writeU8(0xbe);
+  p.writeU8(0x04);
+  p.writeBytes(utils.ripesha(publicKey));
+  p.writeChecksum();
 
-  return utils.toBase58(id);
+  return utils.toBase58(p.render());
 };
 
 Wallet.prototype.createReceive = function createReceive() {
@@ -534,6 +537,7 @@ Wallet.prototype.fill = function fill(tx, options, callback) {
     try {
       tx.fill(coins, {
         selection: options.selection || 'age',
+        accurate: options.accurate,
         confirmed: options.confirmed,
         free: options.free,
         fee: options.fee,
@@ -574,7 +578,7 @@ Wallet.prototype.getTX = function getTX(hash, callback) {
 
 Wallet.prototype.createTX = function createTX(options, outputs, callback) {
   var self = this;
-  var tx;
+  var tx, i;
 
   if (typeof outputs === 'function') {
     callback = outputs;
@@ -593,9 +597,8 @@ Wallet.prototype.createTX = function createTX(options, outputs, callback) {
   tx = bcoin.mtx();
 
   // Add the outputs
-  outputs.forEach(function(output) {
-    tx.addOutput(output);
-  });
+  for (i = 0; i < outputs.length; i++)
+    tx.addOutput(outputs[i]);
 
   // Fill the inputs with unspents
   this.fill(tx, options, function(err) {
@@ -620,12 +623,12 @@ Wallet.prototype.createTX = function createTX(options, outputs, callback) {
   });
 };
 
-Wallet.prototype.deriveInput = function deriveInput(tx, i) {
-  return this.deriveInputs(tx.inputs[i])[0];
+Wallet.prototype.deriveInput = function deriveInput(tx, index) {
+  return this.deriveInputs(tx, index)[0];
 };
 
-Wallet.prototype.deriveInputs = function deriveInputs(tx) {
-  var paths = this.getInputPaths(tx);
+Wallet.prototype.deriveInputs = function deriveInputs(tx, index) {
+  var paths = this.getInputPaths(tx, index);
   var addresses = [];
   var i;
 
@@ -641,9 +644,9 @@ Wallet.prototype.getPath = function getPath(address) {
   return this.addressMap[address];
 };
 
-Wallet.prototype.getInputPaths = function getInputPaths(tx) {
+Wallet.prototype.getInputPaths = function getInputPaths(tx, index) {
   var paths = [];
-  var i, input, output, address, path;
+  var i, input, address, path;
 
   if (tx instanceof bcoin.input) {
     path = this.getPath(tx.coin.getAddress());
@@ -654,10 +657,13 @@ Wallet.prototype.getInputPaths = function getInputPaths(tx) {
 
   for (i = 0; i < tx.inputs.length; i++) {
     input = tx.inputs[i];
-    output = input.coin;
-    assert(output);
 
-    address = output.getAddress();
+    if (index != null && i !== index)
+      continue;
+
+    assert(input.coin, 'Not all coins available.');
+
+    address = input.coin.getAddress();
     path = this.getPath(address);
 
     if (!path)
@@ -669,7 +675,7 @@ Wallet.prototype.getInputPaths = function getInputPaths(tx) {
   return utils.uniqs(paths);
 };
 
-Wallet.prototype.getOutputPaths = function getOutputPaths(tx) {
+Wallet.prototype.getOutputPaths = function getOutputPaths(tx, index) {
   var paths = [];
   var i, output, address, path;
 
@@ -683,6 +689,9 @@ Wallet.prototype.getOutputPaths = function getOutputPaths(tx) {
   for (i = 0; i < tx.outputs.length; i++) {
     output = tx.outputs[i];
 
+    if (index != null && i !== index)
+      continue;
+
     address = output.getAddress();
     path = this.getPath(address);
 
@@ -733,6 +742,9 @@ Wallet.prototype.syncOutputDepth = function syncOutputDepth(tx) {
 Wallet.prototype.getRedeem = function getRedeem(hash, prefix) {
   var addr, address;
 
+  if (typeof hash === 'string')
+    hash = new Buffer(hash, 'hex');
+
   if (!prefix) {
     if (hash.length === 20)
       prefix = 'scripthash';
@@ -868,7 +880,7 @@ Wallet.prototype._scan = function _scan(options, txByAddress, callback) {
 };
 
 Wallet.prototype.scriptInputs = function scriptInputs(tx, index) {
-  var addresses = this.deriveInputs(tx);
+  var addresses = this.deriveInputs(tx, index);
   var total = 0;
   var i;
 
@@ -878,24 +890,24 @@ Wallet.prototype.scriptInputs = function scriptInputs(tx, index) {
   return total;
 };
 
-Wallet.prototype.signInputs = function signInputs(tx, type, index) {
-  var addresses = this.deriveInputs(tx);
+Wallet.prototype.signInputs = function signInputs(tx, index, type) {
+  var addresses = this.deriveInputs(tx, index);
   var total = 0;
   var i;
 
   for (i = 0; i < addresses.length; i++)
-    total += addresses[i].signInputs(tx, type, index);
+    total += addresses[i].signInputs(tx, index, type);
 
   return total;
 };
 
-Wallet.prototype.sign = function sign(tx, type, index) {
-  var addresses = this.deriveInputs(tx);
+Wallet.prototype.sign = function sign(tx, index, type) {
+  var addresses = this.deriveInputs(tx, index);
   var total = 0;
   var i;
 
   for (i = 0; i < addresses.length; i++)
-    total += addresses[i].sign(tx, type, index);
+    total += addresses[i].sign(tx, index, type);
 
   return total;
 };
diff --git a/lib/bcoin/walletdb.js b/lib/bcoin/walletdb.js
index ac235beb..a2f8cb74 100644
--- a/lib/bcoin/walletdb.js
+++ b/lib/bcoin/walletdb.js
@@ -79,6 +79,7 @@ WalletDB.prototype._init = function _init() {
   this.db = bcoin.ldb({
     name: this.options.name || 'wallet',
     location: this.options.location,
+    db: this.options.db,
     cacheSize: 8 << 20,
     writeBufferSize: 4 << 20
   });
diff --git a/test/wallet-test.js b/test/wallet-test.js
index 2edd4129..d0ff7c11 100644
--- a/test/wallet-test.js
+++ b/test/wallet-test.js
@@ -370,8 +370,8 @@ describe('Wallet', function() {
                   tx.addInput(coins1[1]);
                   tx.addInput(coins1[2]);
                   tx.addInput(coins2[1]);
-                  assert.equal(w1.sign(tx, 'all'), 2);
-                  assert.equal(w2.sign(tx, 'all'), 1);
+                  assert.equal(w1.sign(tx), 2);
+                  assert.equal(w2.sign(tx), 1);
 
                   // Verify
                   assert.equal(tx.verify(), true);