diff --git a/src/block.ts b/src/block.ts
index f91ad32..d79de9d 100644
--- a/src/block.ts
+++ b/src/block.ts
@@ -1,6 +1,7 @@
 import { Transaction } from './transaction'
 import * as types from './types'
 import * as bcrypto from './crypto'
+import { reverseBuffer } from './bufferutils'
 const Buffer = require('safe-buffer').Buffer
 const fastMerkleRoot = require('merkle-lib/fastRoot')
 const typeforce = require('typeforce')
@@ -153,7 +154,7 @@ export class Block {
   }
 
   getId (): string {
-    return Buffer.from(this.getHash().reverse()).toString('hex')
+    return reverseBuffer(this.getHash()).toString('hex')
   }
 
   getUTCDate (): Date {
@@ -223,7 +224,7 @@ export class Block {
   }
 
   checkProofOfWork (): boolean {
-    const hash: Buffer = Buffer.from(this.getHash().reverse())
+    const hash: Buffer = reverseBuffer(this.getHash())
     const target = Block.calculateTarget(this.bits)
 
     return hash.compare(target) <= 0
diff --git a/src/bufferutils.ts b/src/bufferutils.ts
index b66c84a..3ef7492 100644
--- a/src/bufferutils.ts
+++ b/src/bufferutils.ts
@@ -22,3 +22,16 @@ export function writeUInt64LE (buffer: Buffer, value: number, offset: number): n
   buffer.writeUInt32LE(Math.floor(value / 0x100000000), offset + 4)
   return offset + 8
 }
+
+export function reverseBuffer (buffer: Buffer): Buffer {
+  if (buffer.length < 1) return buffer
+  let j = buffer.length - 1
+  let tmp = 0
+  for (let i = 0; i < buffer.length / 2; i++) {
+    tmp = buffer[i]
+    buffer[i] = buffer[j]
+    buffer[j] = tmp
+    j--
+  }
+  return buffer
+}
diff --git a/src/ecpair.ts b/src/ecpair.ts
index 9a54b1a..321a5ed 100644
--- a/src/ecpair.ts
+++ b/src/ecpair.ts
@@ -33,14 +33,16 @@ class ECPair implements ECPairInterface {
   network: Network
   private __d: Buffer | null
   private __Q: Buffer | null
-  constructor (d: Buffer | null, Q: Buffer | null, options: ECPairOptions) {
+
+  constructor (d?: Buffer, Q?: Buffer, options?: ECPairOptions) {
     if (options === undefined) options = {}
     this.compressed = options.compressed === undefined ? true : options.compressed
     this.network = options.network || NETWORKS.bitcoin
 
-    this.__d = d || null
+    this.__d = null
     this.__Q = null
-    if (Q) this.__Q = ecc.pointCompress(Q, this.compressed)
+    if (d !== undefined) this.__d = d
+    if (Q !== undefined) this.__Q = ecc.pointCompress(Q, this.compressed)
   }
 
   get privateKey (): Buffer | null {
@@ -72,16 +74,16 @@ function fromPrivateKey (buffer: Buffer, options?: ECPairOptions): ECPair {
   if (!ecc.isPrivate(buffer)) throw new TypeError('Private key not in range [1, n)')
   typeforce(isOptions, options)
 
-  return new ECPair(buffer, null, <ECPairOptions>options)
+  return new ECPair(buffer, undefined, <ECPairOptions>options)
 }
 
 function fromPublicKey (buffer: Buffer, options?: ECPairOptions): ECPair {
   typeforce(ecc.isPoint, buffer)
   typeforce(isOptions, options)
-  return new ECPair(null, buffer, <ECPairOptions>options)
+  return new ECPair(undefined, buffer, <ECPairOptions>options)
 }
 
-function fromWIF (string: string, network: Network | Array<Network>): ECPair {
+function fromWIF (string: string, network?: Network | Array<Network>): ECPair {
   const decoded = wif.decode(string)
   const version = decoded.version
 
diff --git a/src/transaction.ts b/src/transaction.ts
index b40e368..515ffb6 100644
--- a/src/transaction.ts
+++ b/src/transaction.ts
@@ -2,6 +2,7 @@ import * as bcrypto from './crypto'
 import * as bscript from './script'
 import * as types from './types'
 import * as bufferutils from './bufferutils'
+import { reverseBuffer } from './bufferutils'
 const Buffer = require('safe-buffer').Buffer
 const opcodes = require('bitcoin-ops')
 const typeforce = require('typeforce')
@@ -74,7 +75,7 @@ export class Transaction {
     this.outs = []
   }
 
-  static fromBuffer (buffer: Buffer, __noStrict: boolean): Transaction {
+  static fromBuffer (buffer: Buffer, __noStrict?: boolean): Transaction {
     let offset: number = 0
 
     function readSlice (n: number): Buffer {
@@ -234,7 +235,7 @@ export class Transaction {
     return this.__byteLength(true)
   }
 
-  __byteLength (__allowWitness: boolean): number {
+  private __byteLength (__allowWitness: boolean): number {
     const hasWitnesses = __allowWitness && this.hasWitnesses()
 
     return (
@@ -454,7 +455,7 @@ export class Transaction {
     return bcrypto.hash256(tbuffer)
   }
 
-  getHash (forWitness: boolean): Buffer {
+  getHash (forWitness?: boolean): Buffer {
     // wtxid for coinbase is always 32 bytes of 0x00
     if (forWitness && this.isCoinbase()) return Buffer.alloc(32, 0)
     return bcrypto.hash256(this.__toBuffer(undefined, undefined, forWitness))
@@ -462,14 +463,14 @@ export class Transaction {
 
   getId (): string {
     // transaction hash's are displayed in reverse order
-    return Buffer.from(this.getHash(false).reverse()).toString('hex')
+    return reverseBuffer(this.getHash(false)).toString('hex')
   }
 
   toBuffer (buffer?: Buffer, initialOffset?: number): Buffer {
     return this.__toBuffer(buffer, initialOffset, true)
   }
 
-  __toBuffer (buffer?: Buffer, initialOffset?: number, __allowWitness?: boolean): Buffer {
+  private __toBuffer (buffer?: Buffer, initialOffset?: number, __allowWitness?: boolean): Buffer {
     if (!buffer) buffer = <Buffer> Buffer.allocUnsafe(this.__byteLength((<boolean>__allowWitness)))
 
     let offset = initialOffset || 0
diff --git a/src/transaction_builder.ts b/src/transaction_builder.ts
index a6b3b48..a920130 100644
--- a/src/transaction_builder.ts
+++ b/src/transaction_builder.ts
@@ -1,5 +1,6 @@
 import { Network } from './networks'
 import * as networks from './networks'
+import { reverseBuffer } from './bufferutils'
 import { Transaction, Output } from './transaction'
 import { ECPairInterface } from './ecpair'
 import * as ECPair from './ecpair'
@@ -131,7 +132,7 @@ export class TransactionBuilder {
     // is it a hex string?
     if (txIsString(txHash)) {
       // transaction hashs's are displayed in reverse order, un-reverse it
-      txHash = <Buffer> Buffer.from(txHash, 'hex').reverse()
+      txHash = reverseBuffer(Buffer.from(txHash, 'hex'))
 
     // is it a Transaction object?
     } else if (txIsTransaction(txHash)) {