diff --git a/README.md b/README.md
index 9dfeb37..730d3e0 100644
--- a/README.md
+++ b/README.md
@@ -12,17 +12,18 @@ Use it in your script:
 
     var encryptor = require('file-encryptor');
 
-    var key = 'My Super Secret Key';
+    var key = crypto.randomBytes(24);
+    var iv = crypto.randomBytes(16);
 
     // Encrypt file.
-    encryptor.encryptFile('input_file.txt', 'encrypted.dat', key, function(err) {
+    encryptor.encryptFile('input_file.txt', 'encrypted.dat', key, iv, function(err) {
       // Encryption complete.
     });
 
     ...
 
     // Decrypt file.
-    encryptor.decryptFile('encrypted.dat', 'output_file.txt', key, function(err) {
+    encryptor.decryptFile('encrypted.dat', 'output_file.txt', key, iv, function(err) {
       // Decryption complete.
     });
 
@@ -40,7 +41,9 @@ Available algorithms can be found by executing:
 
 Setting algorithm option:
 
-    var key = 'My Super Secret Key';
+    var key = crypto.randomBytes(32);
+    var iv = crypto.randomBytes(16);
+        
     var options = { algorithm: 'aes256' };
 
     encryptor.encryptFile('input_file.txt', 'encrypted.dat', key, options, function(err) {
diff --git a/lib/file-encryptor.js b/lib/file-encryptor.js
index 33deefe..8407607 100644
--- a/lib/file-encryptor.js
+++ b/lib/file-encryptor.js
@@ -3,7 +3,7 @@ var crypto = require('crypto'),
 
 var Encryptor = {};
 
-Encryptor.encryptFile = function(inputPath, outputPath, key, options, callback) {
+Encryptor.encryptFile = function(inputPath, outputPath, key, iv, options, callback) {
 
   if(typeof options === 'function') {
     callback = options;
@@ -12,20 +12,21 @@ Encryptor.encryptFile = function(inputPath, outputPath, key, options, callback)
 
   options = Encryptor.combineOptions(options);
 
-  var keyBuf = new Buffer(key);
+  var keyBuf = Buffer.from(key);
+  var ivBuf  = Buffer.from(iv);
 
   var inputStream = fs.createReadStream(inputPath);
   var outputStream = fs.createWriteStream(outputPath);
-  var cipher = crypto.createCipher(options.algorithm, keyBuf);
+  var cipher = crypto.createCipheriv(options.algorithm, keyBuf, ivBuf);
 
   inputStream.on('data', function(data) {
-    var buf = new Buffer(cipher.update(data), 'binary');
+    var buf = Buffer.from(cipher.update(data), 'binary');
     outputStream.write(buf);
   });
 
   inputStream.on('end', function() {
     try {
-      var buf = new Buffer(cipher.final('binary'), 'binary');
+      var buf = Buffer.from(cipher.final('binary'), 'binary');
       outputStream.write(buf);
       outputStream.end();
       outputStream.on('close', function() {
@@ -38,7 +39,7 @@ Encryptor.encryptFile = function(inputPath, outputPath, key, options, callback)
   });
 };
 
-Encryptor.decryptFile = function(inputPath, outputPath, key, options, callback) {
+Encryptor.decryptFile = function(inputPath, outputPath, key, iv, options, callback) {
 
   if(typeof options === 'function') {
     callback = options;
@@ -47,20 +48,21 @@ Encryptor.decryptFile = function(inputPath, outputPath, key, options, callback)
 
   options = Encryptor.combineOptions(options);
 
-  var keyBuf = new Buffer(key);
+  var keyBuf = Buffer.from(key);
+  var ivBuf  = Buffer.from(iv);
 
   var inputStream = fs.createReadStream(inputPath);
   var outputStream = fs.createWriteStream(outputPath);
-  var cipher = crypto.createDecipher(options.algorithm, keyBuf);
+  var cipher = crypto.createDecipheriv(options.algorithm, keyBuf, ivBuf);
 
   inputStream.on('data', function(data) {
-    var buf = new Buffer(cipher.update(data), 'binary');
+    var buf = Buffer.from(cipher.update(data), 'binary');
     outputStream.write(buf);
   });
 
   inputStream.on('end', function() {
     try {
-      var buf = new Buffer(cipher.final('binary'), 'binary');
+      var buf = Buffer.from(cipher.final('binary'), 'binary');
       outputStream.write(buf);
       outputStream.end();
       outputStream.on('close', function() {
diff --git a/test/basic.js b/test/basic.js
index 5242139..5103b04 100644
--- a/test/basic.js
+++ b/test/basic.js
@@ -1,14 +1,18 @@
-var encryptor = require('../lib/file-encryptor'),
+var crypto = require('crypto'),
+    encryptor = require('../lib/file-encryptor'),
     fs = require('fs'),
     path = require('path');
 
-var key = 'My Super Secret Key';
+var key = crypto.randomBytes(32);
+var iv = crypto.randomBytes(16);
 
 var encrypt = function(input) {
   encryptor.encryptFile(
     path.join(__dirname, input),
     path.join(__dirname, input + '.data'),
     key,
+    iv,
+    { algorithm: 'aes256' },
     function(err) {
       console.log(input + ' encryption complete.');
       decrypt(input, input + '.data');
@@ -21,6 +25,8 @@ var decrypt = function(original, encrypted) {
     path.join(__dirname, encrypted),
     path.join(__dirname, 'decrypted.' + original),
     key,
+    iv,
+    { algorithm: 'aes256' },
     function(err) {
       console.log(original + ' decryption complete.');
     }