diff --git a/src/address.js b/src/address.js
index 5624f19..0def957 100644
--- a/src/address.js
+++ b/src/address.js
@@ -1,7 +1,8 @@
 var base58check = require('bs58check')
-var typeForce = require('typeforce')
+var typeforce = require('typeforce')
 var networks = require('./networks')
 var scripts = require('./scripts')
+var types = require('./types')
 
 function fromBase58Check (string) {
   var payload = base58check.decode(string)
@@ -23,10 +24,7 @@ function fromOutputScript (script, network) {
 }
 
 function toBase58Check (hash, version) {
-  typeForce('Buffer', hash)
-
-  if (hash.length !== 20) throw new TypeError('Invalid hash length')
-  if (version & ~0xff) throw new TypeError('Invalid version byte')
+  typeforce(types.tuple(types.Hash160bit, types.UInt8), arguments)
 
   var payload = new Buffer(21)
   payload.writeUInt8(version, 0)
diff --git a/src/ecdsa.js b/src/ecdsa.js
index 0a07412..701285f 100644
--- a/src/ecdsa.js
+++ b/src/ecdsa.js
@@ -1,6 +1,6 @@
-var assert = require('assert')
 var createHmac = require('create-hmac')
-var typeForce = require('typeforce')
+var typeforce = require('typeforce')
+var types = require('./types')
 
 var BigInteger = require('bigi')
 var ECSignature = require('./ecsignature')
@@ -10,12 +10,12 @@ var ONE = new Buffer([1])
 
 // https://tools.ietf.org/html/rfc6979#section-3.2
 function deterministicGenerateK (curve, hash, d, checkSig) {
-  typeForce('Buffer', hash)
-  typeForce('BigInteger', d)
-  typeForce('Function', checkSig)
-
-  // sanity check
-  assert.equal(hash.length, 32, 'Hash must be 256 bit')
+  typeforce(types.tuple(
+    types.ECCurve,
+    types.Hash256bit,
+    types.BigInt,
+    types.Function
+  ), arguments)
 
   var x = d.toBuffer(32)
   var k = new Buffer(32)
@@ -75,9 +75,7 @@ function deterministicGenerateK (curve, hash, d, checkSig) {
 }
 
 function sign (curve, hash, d) {
-  typeForce('Curve', curve)
-  typeForce('Buffer', hash)
-  typeForce('BigInteger', d)
+  typeforce(types.tuple(types.ECCurve, types.Hash256bit, types.BigInt), arguments)
 
   var e = BigInteger.fromBuffer(hash)
   var n = curve.n
@@ -109,10 +107,11 @@ function sign (curve, hash, d) {
 }
 
 function verify (curve, hash, signature, Q) {
-  typeForce('Curve', curve)
-  typeForce('Buffer', hash)
-  typeForce('ECSignature', signature)
-  typeForce('Point', Q)
+  typeforce(types.tuple(types.ECCurve,
+    types.Hash256bit,
+    types.ECSignature,
+    types.ECPoint
+  ), arguments)
 
   var n = curve.n
   var G = curve.G
@@ -162,20 +161,20 @@ function verify (curve, hash, signature, Q) {
   * http://www.secg.org/download/aid-780/sec1-v2.pdf
   */
 function recoverPubKey (curve, e, signature, i) {
-  typeForce('Curve', curve)
-  typeForce('BigInteger', e)
-  typeForce('ECSignature', signature)
-  typeForce('Number', i)
-  assert.strictEqual(i & 3, i, 'Recovery param is more than two bits')
+  typeforce(types.tuple(
+    types.ECCurve,
+    types.BigInt,
+    types.ECSignature,
+    types.UInt2
+  ), arguments)
 
   var n = curve.n
   var G = curve.G
-
   var r = signature.r
   var s = signature.s
 
-  assert(r.signum() > 0 && r.compareTo(n) < 0, 'Invalid r value')
-  assert(s.signum() > 0 && s.compareTo(n) < 0, 'Invalid s value')
+  if (r.signum() <= 0 || r.compareTo(n) >= 0) throw new Error('Invalid r value')
+  if (s.signum() <= 0 || s.compareTo(n) >= 0) throw new Error('Invalid s value')
 
   // A set LSB signifies that the y-coordinate is odd
   var isYOdd = i & 1
@@ -190,7 +189,7 @@ function recoverPubKey (curve, e, signature, i) {
 
   // 1.4 Check that nR is at infinity
   var nR = R.multiply(n)
-  assert(curve.isInfinity(nR), 'nR is not a valid curve point')
+  if (!curve.isInfinity(nR)) throw new Error('nR is not a valid curve point')
 
   // Compute r^-1
   var rInv = r.modInverse(n)
@@ -219,10 +218,12 @@ function recoverPubKey (curve, e, signature, i) {
   * that resulted in a successful pubkey recovery.
   */
 function calcPubKeyRecoveryParam (curve, e, signature, Q) {
-  typeForce('Curve', curve)
-  typeForce('BigInteger', e)
-  typeForce('ECSignature', signature)
-  typeForce('Point', Q)
+  typeforce(types.tuple(
+    types.ECCurve,
+    types.BigInt,
+    types.ECSignature,
+    types.ECPoint
+  ), arguments)
 
   for (var i = 0; i < 4; i++) {
     var Qprime = recoverPubKey(curve, e, signature, i)
diff --git a/src/ecpair.js b/src/ecpair.js
index 8279428..f9c55b5 100644
--- a/src/ecpair.js
+++ b/src/ecpair.js
@@ -5,34 +5,34 @@ var ecdsa = require('./ecdsa')
 var ecurve = require('ecurve')
 var NETWORKS = require('./networks')
 var randomBytes = require('randombytes')
-var typeForce = require('typeforce')
+var typeforce = require('typeforce')
+var types = require('./types')
 
 var BigInteger = require('bigi')
 
 function ECPair (d, Q, options) {
   options = options || {}
 
-  var compressed = options.compressed === undefined ? true : options.compressed
-  var network = options.network === undefined ? NETWORKS.bitcoin : options.network
-
-  typeForce('Boolean', compressed)
-  assert('pubKeyHash' in network, 'Unknown pubKeyHash constants for network')
+  typeforce({
+    compressed: types.maybe(types.Boolean),
+    network: types.maybe(types.Network)
+  }, options)
 
   if (d) {
-    assert(d.signum() > 0, 'Private key must be greater than 0')
-    assert(d.compareTo(ECPair.curve.n) < 0, 'Private key must be less than the curve order')
+    if (d.signum() <= 0) throw new Error('Private key must be greater than 0')
+    if (d.compareTo(ECPair.curve.n) >= 0) throw new Error('Private key must be less than the curve order')
+    if (Q) throw new TypeError('Unexpected publicKey parameter')
 
-    assert(!Q, 'Unexpected publicKey parameter')
     this.d = d
 
-  // enforce Q is a public key if no private key given
   } else {
-    typeForce('Point', Q)
+    typeforce(types.ECPoint, Q)
+
     this.__Q = Q
   }
 
-  this.compressed = compressed
-  this.network = network
+  this.compressed = options.compressed === undefined ? true : options.compressed
+  this.network = options.network || NETWORKS.bitcoin
 }
 
 Object.defineProperty(ECPair.prototype, 'Q', {
@@ -106,8 +106,7 @@ ECPair.makeRandom = function (options) {
 
   var rng = options.rng || randomBytes
   var buffer = rng(32)
-  typeForce('Buffer', buffer)
-  assert.equal(buffer.length, 32, 'Expected 256-bit Buffer from RNG')
+  typeforce(types.Buffer256bit, buffer)
 
   var d = BigInteger.fromBuffer(buffer)
   d = d.mod(ECPair.curve.n)
diff --git a/src/ecsignature.js b/src/ecsignature.js
index 151e962..b17ed8b 100644
--- a/src/ecsignature.js
+++ b/src/ecsignature.js
@@ -1,11 +1,12 @@
 var assert = require('assert')
-var typeForce = require('typeforce')
+var typeforce = require('typeforce')
+var types = require('./types')
 
 var BigInteger = require('bigi')
 
 function ECSignature (r, s) {
-  typeForce('BigInteger', r)
-  typeForce('BigInteger', s)
+  typeforce(types.BigInt, r)
+  typeforce(types.BigInt, s)
 
   this.r = r
   this.s = s
diff --git a/src/message.js b/src/message.js
index 75a3e2e..bced6dc 100644
--- a/src/message.js
+++ b/src/message.js
@@ -41,6 +41,7 @@ function verify (address, signature, message, network) {
   var parsed = ECSignature.parseCompact(signature)
   var e = BigInteger.fromBuffer(hash)
   var Q = ecdsa.recoverPubKey(ecparams, e, parsed.signature, parsed.i)
+
   var keyPair = new ECPair(null, Q, {
     compressed: parsed.compressed,
     network: network
diff --git a/src/script.js b/src/script.js
index 141fb1f..12d21e4 100644
--- a/src/script.js
+++ b/src/script.js
@@ -1,12 +1,12 @@
 var assert = require('assert')
 var bufferutils = require('./bufferutils')
 var crypto = require('./crypto')
-var typeForce = require('typeforce')
+var typeforce = require('typeforce')
+var types = require('./types')
 var opcodes = require('./opcodes')
 
 function Script (buffer, chunks) {
-  typeForce('Buffer', buffer)
-  typeForce('Array', chunks)
+  typeforce(types.tuple(types.Buffer, types.Array), arguments)
 
   this.buffer = buffer
   this.chunks = chunks
@@ -63,7 +63,7 @@ Script.fromBuffer = function (buffer) {
 }
 
 Script.fromChunks = function (chunks) {
-  typeForce('Array', chunks)
+  typeforce(types.Array, chunks)
 
   var bufferSize = chunks.reduce(function (accum, chunk) {
     // data chunk
diff --git a/src/scripts.js b/src/scripts.js
index c9e4978..8b57f08 100644
--- a/src/scripts.js
+++ b/src/scripts.js
@@ -1,6 +1,7 @@
 var assert = require('assert')
 var ops = require('./opcodes')
-var typeForce = require('typeforce')
+var typeforce = require('typeforce')
+var types = require('./types')
 
 var ecurve = require('ecurve')
 var curve = ecurve.getCurveByName('secp256k1')
@@ -134,7 +135,7 @@ function isNullDataOutput (script) {
 }
 
 function classifyOutput (script) {
-  typeForce('Script', script)
+  typeforce(types.Script, script)
 
   if (isPubKeyHashOutput(script)) {
     return 'pubkeyhash'
@@ -152,7 +153,7 @@ function classifyOutput (script) {
 }
 
 function classifyInput (script, allowIncomplete) {
-  typeForce('Script', script)
+  typeforce(types.Script, script)
 
   if (isPubKeyHashInput(script)) {
     return 'pubkeyhash'
@@ -178,7 +179,7 @@ function pubKeyOutput (pubKey) {
 
 // OP_DUP OP_HASH160 {pubKeyHash} OP_EQUALVERIFY OP_CHECKSIG
 function pubKeyHashOutput (hash) {
-  typeForce('Buffer', hash)
+  typeforce(types.Hash160bit, hash)
 
   return Script.fromChunks([
     ops.OP_DUP,
@@ -191,7 +192,7 @@ function pubKeyHashOutput (hash) {
 
 // OP_HASH160 {scriptHash} OP_EQUAL
 function scriptHashOutput (hash) {
-  typeForce('Buffer', hash)
+  typeforce(types.Hash160bit, hash)
 
   return Script.fromChunks([
     ops.OP_HASH160,
@@ -202,7 +203,7 @@ function scriptHashOutput (hash) {
 
 // m [pubKeys ...] n OP_CHECKMULTISIG
 function multisigOutput (m, pubKeys) {
-  typeForce(['Buffer'], pubKeys)
+  typeforce(types.tuple(types.Number, [types.Buffer]), arguments)
 
   var n = pubKeys.length
   assert(n >= m, 'Not enough pubKeys provided')
@@ -217,15 +218,14 @@ function multisigOutput (m, pubKeys) {
 
 // {signature}
 function pubKeyInput (signature) {
-  typeForce('Buffer', signature)
+  typeforce(types.Buffer, signature)
 
   return Script.fromChunks([signature])
 }
 
 // {signature} {pubKey}
 function pubKeyHashInput (signature, pubKey) {
-  typeForce('Buffer', signature)
-  typeForce('Buffer', pubKey)
+  typeforce(types.tuple(types.Buffer, types.Buffer), arguments)
 
   return Script.fromChunks([signature, pubKey])
 }
diff --git a/src/transaction.js b/src/transaction.js
index 95cd2be..3a83193 100644
--- a/src/transaction.js
+++ b/src/transaction.js
@@ -1,7 +1,8 @@
 var assert = require('assert')
 var bufferutils = require('./bufferutils')
 var crypto = require('./crypto')
-var typeForce = require('typeforce')
+var typeforce = require('typeforce')
+var types = require('./types')
 var opcodes = require('./opcodes')
 
 var Script = require('./script')
@@ -104,19 +105,19 @@ Transaction.isCoinbaseHash = function (buffer) {
 }
 
 Transaction.prototype.addInput = function (hash, index, sequence, script) {
-  if (sequence === undefined || sequence === null) {
+  typeforce(types.tuple(
+    types.Hash256bit,
+    types.UInt32,
+    types.maybe(types.UInt32),
+    types.maybe(types.Script)
+  ), arguments)
+
+  if (types.Null(sequence)) {
     sequence = Transaction.DEFAULT_SEQUENCE
   }
 
   script = script || Script.EMPTY
 
-  typeForce('Buffer', hash)
-  typeForce('Number', index)
-  typeForce('Number', sequence)
-  typeForce('Script', script)
-
-  assert.equal(hash.length, 32, 'Expected hash length of 32, got ' + hash.length)
-
   // Add the input and return the input's index
   return (this.ins.push({
     hash: hash,
@@ -127,8 +128,7 @@ Transaction.prototype.addInput = function (hash, index, sequence, script) {
 }
 
 Transaction.prototype.addOutput = function (scriptPubKey, value) {
-  typeForce('Script', scriptPubKey)
-  typeForce('Number', value)
+  typeforce(types.tuple(types.Script, types.UInt53), arguments)
 
   // Add the output and return the output's index
   return (this.outs.push({
@@ -188,11 +188,7 @@ var ONE = new Buffer('0000000000000000000000000000000000000000000000000000000000
  * This hash can then be used to sign the provided transaction input.
  */
 Transaction.prototype.hashForSignature = function (inIndex, prevOutScript, hashType) {
-  typeForce('Number', inIndex)
-  typeForce('Script', prevOutScript)
-  typeForce('Number', hashType)
-
-  assert(inIndex >= 0, 'Invalid vin index')
+  typeforce(types.tuple(types.UInt32, types.Script, /* types.UInt8 */ types.Number), arguments)
 
   // https://github.com/bitcoin/bitcoin/blob/master/src/test/sighash_tests.cpp#L29
   if (inIndex >= this.ins.length) return ONE
@@ -327,8 +323,7 @@ Transaction.prototype.toHex = function () {
 }
 
 Transaction.prototype.setInputScript = function (index, script) {
-  typeForce('Number', index)
-  typeForce('Script', script)
+  typeforce(types.tuple(types.Number, types.Script), arguments)
 
   this.ins[index].script = script
 }
diff --git a/src/types.js b/src/types.js
new file mode 100644
index 0000000..ad8d62c
--- /dev/null
+++ b/src/types.js
@@ -0,0 +1,71 @@
+var bigi = require('bigi')
+var ecurve = require('ecurve')
+var typeforce = require('typeforce')
+
+function nBuffer (value, n) {
+  if (!Buffer.isBuffer(value)) return false
+  if (value.length !== n) throw new Error('Expected ' + (n * 8) + '-bit Buffer, got ' + (value.length * 8) + '-bit')
+  return true
+}
+
+function Hash160bit (value) { return nBuffer(value, 20) }
+function Hash256bit (value) { return nBuffer(value, 32) }
+function Buffer256bit (value) { return nBuffer(value, 32) }
+
+var UINT53_MAX = Math.pow(2, 53) - 1
+function UInt2 (value) { return (value & 3) === value }
+function UInt8 (value) { return (value & 0xff) === value }
+function UInt32 (value) { return (value >>> 0) === value }
+function UInt53 (value) {
+  return typeforce.Number(value) &&
+    value >= 0 &&
+    value <= UINT53_MAX &&
+    Math.floor(value) === value
+}
+
+// external dependent types
+function BigInt (value) { return !typeforce.Null(value) && value.constructor === bigi }
+function ECCurve (value) { return !typeforce.Null(value) && value.constructor === ecurve.Curve }
+function ECPoint (value) { return !typeforce.Null(value) && value.constructor === ecurve.Point }
+
+// exposed, external API
+var ECSignature = typeforce.compile({ r: BigInt, s: BigInt })
+var Network = typeforce.compile({
+  messagePrefix: typeforce.oneOf(typeforce.Buffer, typeforce.String),
+  bip32: {
+    public: UInt32,
+    private: UInt32
+  },
+  pubKeyHash: UInt8,
+  scriptHash: UInt8,
+  wif: UInt8,
+  dustThreshold: typeforce.Number
+})
+
+var Script = typeforce.compile({
+  buffer: typeforce.Buffer,
+  chunks: typeforce.arrayOf(typeforce.oneOf(typeforce.Number, typeforce.Buffer))
+})
+
+// extend typeforce types with ours
+var types = {
+  BigInt: BigInt,
+  Buffer256bit: Buffer256bit,
+  ECCurve: ECCurve,
+  ECPoint: ECPoint,
+  ECSignature: ECSignature,
+  Hash160bit: Hash160bit,
+  Hash256bit: Hash256bit,
+  Network: Network,
+  Script: Script,
+  UInt2: UInt2,
+  UInt8: UInt8,
+  UInt32: UInt32,
+  UInt53: UInt53
+}
+
+for (var typeName in typeforce) {
+  types[typeName] = typeforce[typeName]
+}
+
+module.exports = types
diff --git a/test/fixtures/ecdsa.json b/test/fixtures/ecdsa.json
index 0205d54..ffd6cba 100644
--- a/test/fixtures/ecdsa.json
+++ b/test/fixtures/ecdsa.json
@@ -188,7 +188,7 @@
       },
       {
         "description": "Invalid i value (> 3)",
-        "exception": "Recovery param is more than two bits",
+        "exception": "Expected UInt2, got Number 4",
         "e": "01",
         "signatureRaw": {
           "r": "00",
diff --git a/test/fixtures/transaction.json b/test/fixtures/transaction.json
index 9710818..a47cf3a 100644
--- a/test/fixtures/transaction.json
+++ b/test/fixtures/transaction.json
@@ -229,12 +229,12 @@
   "invalid": {
     "addInput": [
       {
-        "exception": "Expected hash length of 32, got 30",
+        "exception": "Expected 256-bit Buffer, got 240-bit",
         "hash": "0aed1366a73b6057ee7800d737bff1bdf8c448e98d86bc0998f2b009816d",
         "index": 0
       },
       {
-        "exception": "Expected hash length of 32, got 34",
+        "exception": "Expected 256-bit Buffer, got 272-bit",
         "hash": "0aed1366a73b6057ee7800d737bff1bdf8c448e98d86bc0998f2b009816da9b0ffff",
         "index": 0
       }