diff --git a/src/File.php b/src/File.php
index 3db66bb..6b44fbb 100644
--- a/src/File.php
+++ b/src/File.php
@@ -59,10 +59,10 @@ public static function createNewRandomKey()
      *
      * @param string $inputFilename
      * @param string $outputFilename
-     * @param string $key
+     * @param Key $key
      * @return boolean
      */
-    public static function encryptFile($inputFilename, $outputFilename, $key)
+    public static function encryptFile($inputFilename, $outputFilename, Key $key)
     {
         if (!\is_string($inputFilename)) {
             throw new Ex\InvalidInput(
@@ -137,10 +137,10 @@ public static function encryptFile($inputFilename, $outputFilename, $key)
      *
      * @param string $inputFilename
      * @param string $outputFilename
-     * @param string $key
+     * @param Key $key
      * @return boolean
      */
-    public static function decryptFile($inputFilename, $outputFilename, $key)
+    public static function decryptFile($inputFilename, $outputFilename, Key $key)
     {
         if (!\is_string($inputFilename)) {
             throw new Ex\InvalidInput(
@@ -215,10 +215,10 @@ public static function decryptFile($inputFilename, $outputFilename, $key)
      *
      * @param resource $inputHandle
      * @param resource $outputHandle
-     * @param string $key
+     * @param Key $key
      * @return boolean
      */
-    public static function encryptResource($inputHandle, $outputHandle, $key)
+    public static function encryptResource($inputHandle, $outputHandle, Key $key)
     {
         // Because we don't have strict typing in PHP 5
         if (!\is_resource($inputHandle)) {
@@ -235,6 +235,8 @@ public static function encryptResource($inputHandle, $outputHandle, $key)
             Core::CURRENT_FILE_VERSION,
             Core::CURRENT_FILE_VERSION
         );
+        $inputStat = \fstat($inputHandle);
+        $inputSize = $inputStat['size'];
 
         // Let's add this check before anything
         if (!\in_array($config->hashFunctionName(), \hash_algos())) {
@@ -243,13 +245,6 @@ public static function encryptResource($inputHandle, $outputHandle, $key)
             );
         }
 
-        // Sanity check; key must be the appropriate length!
-        if (Core::ourStrlen($key) !== $config->keyByteSize()) {
-            throw new Ex\InvalidInput(
-                'Invalid key length. Keys should be '.$config->keyByteSize().' bytes long.'
-            );
-        }
-
         /**
          *  Let's split our keys
          */
@@ -258,7 +253,7 @@ public static function encryptResource($inputHandle, $outputHandle, $key)
         // $ekey -- Encryption Key -- used for AES
         $ekey = Core::HKDF(
             $config->hashFunctionName(),
-            $key,
+            $key->getRawBytes(),
             $config->keyByteSize(),
             $config->encryptionInfoString(),
             $file_salt,
@@ -268,7 +263,7 @@ public static function encryptResource($inputHandle, $outputHandle, $key)
         // $akey -- Authentication Key -- used for HMAC
         $akey = Core::HKDF(
             $config->hashFunctionName(),
-            $key,
+            $key->getRawBytes(),
             $config->keyByteSize(),
             $config->authenticationInfoString(),
             $file_salt,
@@ -290,15 +285,11 @@ public static function encryptResource($inputHandle, $outputHandle, $key)
         /**
          * First let's write our header, file salt, and IV to the first N blocks of the output file
          */
-        if (\fwrite(
+        self::writeBytes(
             $outputHandle,
             Core::CURRENT_FILE_VERSION . $file_salt . $iv, 
             Core::HEADER_VERSION_SIZE + $config->saltByteSize() + $ivsize
-        ) === false) {
-            throw new Ex\CannotPerformOperationException(
-                'Cannot write to output file'
-            );
-        }
+        );
 
         /**
          * We're going to initialize a HMAC-SHA256 with the given $akey
@@ -333,11 +324,20 @@ public static function encryptResource($inputHandle, $outputHandle, $key)
         /**
          * Iterate until we reach the end of the input file
          */
+        $breakR = false;
         while (!\feof($inputHandle)) {
-            $read = \fread($inputHandle, $config->bufferByteSize());
-            if ($read === false) {
-                throw new Ex\CannotPerformOperationException(
-                    'Cannot read input file'
+            $pos = \ftell($inputHandle);
+            if ($pos + $config->bufferByteSize() >= $inputSize) {
+                $breakR = true;
+                // We need to break after this loop iteration
+                $read = self::readBytes(
+                    $inputHandle,
+                    $inputSize - $pos
+                );
+            } else {
+                $read = self::readBytes(
+                    $inputHandle,
+                    $config->bufferByteSize()
                 );
             }
             $thisIv = Core::incrementCounter($thisIv, $inc, $config);
@@ -364,27 +364,21 @@ public static function encryptResource($inputHandle, $outputHandle, $key)
             /**
              * Write the ciphertext to the output file
              */
-            if (\fwrite($outputHandle, $encrypted, Core::ourStrlen($encrypted)) === false) {
-                throw new Ex\CannotPerformOperationException(
-                    'Cannot write to output file during encryption'
-                );
-            }
+            self::writeBytes($outputHandle, $encrypted, Core::ourStrlen($encrypted));
 
             /**
              * Update the HMAC for the entire file with the data from this block
              */
             \hash_update($hmac, $encrypted);
+            if ($breakR) {
+                break;
+            }
         }
 
         // Now let's get our HMAC and append it
         $finalHMAC = \hash_final($hmac, true);
 
-        $appended = \fwrite($outputHandle, $finalHMAC, $config->macByteSize());
-        if ($appended === false) {
-            throw new Ex\CannotPerformOperationException(
-                'Cannot write to output file'
-            );
-        }
+        self::writeBytes($outputHandle, $finalHMAC, $config->macByteSize());
         return true;
     }
 
@@ -394,10 +388,10 @@ public static function encryptResource($inputHandle, $outputHandle, $key)
      *
      * @param resource $inputHandle
      * @param resource $outputHandle
-     * @param string $key
+     * @param Key $key
      * @return boolean
      */
-    public static function decryptResource($inputHandle, $outputHandle, $key)
+    public static function decryptResource($inputHandle, $outputHandle, Key $key)
     {
         // Because we don't have strict typing in PHP 5
         if (!\is_resource($inputHandle)) {
@@ -412,13 +406,7 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
         }
 
         // Parse the header.
-        $header = '';
-        $remaining = Core::HEADER_VERSION_SIZE;
-        do {
-            $header .= \fread($inputHandle, $remaining);
-            $remaining = Core::HEADER_VERSION_SIZE - Core::ourStrlen($header);
-        } while ($remaining > 0);
-
+        $header = self::readBytes($inputHandle, Core::HEADER_VERSION_SIZE);
         $config = self::getFileVersionConfigFromHeader(
             $header,
             Core::CURRENT_FILE_VERSION
@@ -430,20 +418,9 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
                 'The specified hash function does not exist'
             );
         }
-
-        // Sanity check; key must be the appropriate length!
-        if (Core::ourStrlen($key) !== $config->keyByteSize()) {
-            throw new Ex\InvalidInput(
-                'Invalid key length. Keys should be '.$config->keyByteSize().' bytes long.'
-            );
-        }
+        
         // Let's grab the file salt.
-        $file_salt = \fread($inputHandle, $config->saltByteSize());
-        if ($file_salt === false ) {
-            throw new Ex\CannotPerformOperationException(
-                'Cannot read input file'
-            );
-        }
+        $file_salt = self::readBytes($inputHandle, $config->saltByteSize());
             
         // For storing MACs of each buffer chunk
         $macs = [];
@@ -458,7 +435,7 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
              */
             $ekey = Core::HKDF(
                 $config->hashFunctionName(),
-                $key,
+                $key->getRawBytes(),
                 $config->keyByteSize(),
                 $config->encryptionInfoString(),
                 $file_salt,
@@ -470,7 +447,7 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
              */
             $akey = Core::HKDF(
                 $config->hashFunctionName(),
-                $key,
+                $key->getRawBytes(),
                 $config->keyByteSize(),
                 $config->authenticationInfoString(),
                 $file_salt,
@@ -483,12 +460,7 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
              * It should be the first N blocks of the file (N = 16)
              */
             $ivsize = \openssl_cipher_iv_length($config->cipherMethod());
-            $iv = \fread($inputHandle, $ivsize);
-            if ($iv === false ) {
-                throw new Ex\CannotPerformOperationException(
-                    'Cannot read input file'
-                );
-            }
+            $iv = self::readBytes($inputHandle, $ivsize);
 
             // How much do we increase the counter after each buffered encryption to prevent nonce reuse
             $inc = $config->bufferByteSize() / $config->blockByteSize();
@@ -516,12 +488,7 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
             --$cipher_end; // We need to subtract one
 
             // We keep our MAC stored in this variable
-            $stored_mac = \fread($inputHandle, $config->macByteSize());
-            if ($stored_mac === false) {
-                throw new Ex\CannotPerformOperationException(
-                    'Cannot read input file'
-                );
-            }
+            $stored_mac = self::readBytes($inputHandle, $config->macByteSize());
 
             /**
              * We begin recalculating the HMAC for the entire file...
@@ -579,9 +546,15 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
                  */
                 if ($pos + $config->bufferByteSize() >= $cipher_end) {
                     $break = true;
-                    $read = \fread($inputHandle, $cipher_end - $pos + 1);
+                    $read = self::readBytes(
+                        $inputHandle,
+                        $cipher_end - $pos + 1
+                    );
                 } else {
-                    $read = \fread($inputHandle, $config->bufferByteSize());
+                    $read = self::readBytes(
+                        $inputHandle,
+                        $config->bufferByteSize()
+                    );
                 }
                 if ($read === false) {
                     throw new Ex\CannotPerformOperationException(
@@ -636,7 +609,6 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
             /**
              * This loop writes plaintext to the destination file:
              */
-            $result = null;
             while (!$breakW) {
                 /**
                  * Get the current position
@@ -654,13 +626,14 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
                  */
                 if ($pos + $config->bufferByteSize() >= $cipher_end) {
                     $breakW = true;
-                    $read = \fread($inputHandle, $cipher_end - $pos + 1);
+                    $read = self::readBytes(
+                        $inputHandle,
+                        $cipher_end - $pos + 1
+                    );
                 } else {
-                    $read = \fread($inputHandle, $config->bufferByteSize());
-                }
-                if ($read === false) {
-                    throw new Ex\CannotPerformOperationException(
-                        'Could not read input file during decryption'
+                    $read = self::readBytes(
+                        $inputHandle,
+                        $config->bufferByteSize()
                     );
                 }
 
@@ -713,23 +686,13 @@ public static function decryptResource($inputHandle, $outputHandle, $key)
                 /**
                  * Write the plaintext out to the output file
                  */
-                $result = \fwrite(
-                    $outputHandle, 
-                    $decrypted, 
+                self::writeBytes(
+                    $outputHandle,
+                    $decrypted,
                     Core::ourStrlen($decrypted)
                 );
-
-                /**
-                 * Check result
-                 */
-                if ($result === false) {
-                    throw new Ex\CannotPerformOperationException(
-                        'Could not write to output file during decryption.'
-                    );
-                }
             }
-        // This should be an integer
-        return $result;
+        return true;
     }
 
     /**
@@ -799,4 +762,81 @@ private static function getFileVersionConfigFromMajorMinor($major, $minor)
             );
         }
     }
+
+    /**
+     * Read from a stream; prevent partial reads
+     *
+     * @param resource $stream
+     * @param int $num
+     * @return string
+     *
+     * @throws \RangeException
+     * @throws Ex\CannotPerformOperationException
+     */
+    final public static function readBytes($stream, $num)
+    {
+        if ($num <= 0) {
+            throw new \RangeException(
+                'Tried to read less than 0 bytes'
+            );
+        }
+        $buf = '';
+        $remaining = $num;
+        while ($remaining > 0 && !\feof($stream)) {
+            $read = \fread($stream, $remaining);
+            
+            if ($read === false) {
+                throw new Ex\CannotPerformOperationException(
+                    'Could not read from the file'
+                );
+            }
+            $buf .= $read;
+            $remaining -= Core::ourStrlen($read);
+        }
+        if (Core::ourStrlen($buf) !== $num) {
+            throw new Ex\CannotPerformOperationException(
+                'Tried to read past the end of the file'
+            );
+        }
+        return $buf;
+    }
+
+    /**
+     * Write to a stream; prevent partial writes
+     *
+     * @param resource $stream
+     * @param string $buf
+     * @param int $num (number of bytes)
+     * @return string
+     * @throws Ex\CannotPerformOperationException
+     */
+    final public static function writeBytes($stream, $buf, $num = null)
+    {
+        $bufSize = Core::ourStrlen($buf);
+        if ($num === null) {
+            $num = $bufSize;
+        }
+        if ($num > $bufSize) {
+            throw new Ex\CannotPerformOperationException(
+                'Trying to write more bytes than the buffer contains.'
+            );
+        }
+        if ($num < 0) {
+            throw new Ex\CannotPerformOperationException(
+                'Tried to write less than 0 bytes'
+            );
+        }
+        $remaining = $num;
+        while ($remaining > 0) {
+            $written = \fwrite($stream, $buf, $remaining);
+            if ($written === false) {
+                throw new Ex\CannotPerformOperationException(
+                    'Could not write to the file'
+                );
+            }
+            $buf = Core::ourSubstr($buf, $written, null);
+            $remaining -= $written;
+        }
+        return $num;
+    }
 }
diff --git a/src/StreamInterface.php b/src/StreamInterface.php
index e31a5e9..0b8a962 100644
--- a/src/StreamInterface.php
+++ b/src/StreamInterface.php
@@ -9,10 +9,10 @@ interface StreamInterface
      * 
      * @param string $inputFilename
      * @param string $outputFilename
-     * @param string $key
+     * @param Key $key
      * @return boolean
      */
-    public static function encryptFile($inputFilename, $outputFilename, $key);
+    public static function encryptFile($inputFilename, $outputFilename, Key $key);
 
     /**
      * Decrypt the contents at $inputFilename, storing the result in $outputFilename
@@ -20,10 +20,10 @@ public static function encryptFile($inputFilename, $outputFilename, $key);
      * 
      * @param string $inputFilename
      * @param string $outputFilename
-     * @param string $key
+     * @param Key $key
      * @return boolean
      */
-    public static function decryptFile($inputFilename, $outputFilename, $key);
+    public static function decryptFile($inputFilename, $outputFilename, Key $key);
 
     /**
      * Encrypt the contents of a file handle $inputHandle and store the results
@@ -31,10 +31,10 @@ public static function decryptFile($inputFilename, $outputFilename, $key);
      * 
      * @param resource $inputHandle
      * @param resource $outputHandle
-     * @param string $key
+     * @param Key $key
      * @return boolean
      */
-    public static function encryptResource($inputHandle, $outputHandle, $key);
+    public static function encryptResource($inputHandle, $outputHandle, Key $key);
 
     /**
      * Decrypt the contents of a file handle $inputHandle and store the results
@@ -42,8 +42,8 @@ public static function encryptResource($inputHandle, $outputHandle, $key);
      * 
      * @param resource $inputHandle
      * @param resource $outputHandle
-     * @param string $key
+     * @param Key $key
      * @return boolean
      */
-    public static function decryptResource($inputHandle, $outputHandle, $key);
+    public static function decryptResource($inputHandle, $outputHandle, Key $key);
 }
diff --git a/test/stream/decrypt.php b/test/stream/decrypt.php
index b9c6a4e..e6710aa 100644
--- a/test/stream/decrypt.php
+++ b/test/stream/decrypt.php
@@ -8,52 +8,65 @@
 
 $mem = 0;
 $start_time = $end_time = \microtime(true);
-$key = \Defuse\Crypto\Encoding::hexToBin(\file_get_contents('key.txt'));
+$key = \Defuse\Crypto\Key::LoadFromAsciiSafeString(\file_get_contents('key.txt'));
+$end_time = \microtime(true);
 
 echo 'Decrypting', "\n", str_repeat('-', 50), "\n\n";
 echo "Load Key:\n\t";
 
-echo \number_format($end_time - $start_time, 2),
+echo \number_format($end_time - $start_time, 4),
     's (Memory: ', \number_format(\memory_get_usage() / 1024, 2), ' KB)',
     "\n";
-$end_time = $start_time;
 
-\Defuse\Crypto\File::decryptFile(
+$start_time = \microtime(true);
+$success = \Defuse\Crypto\File::decryptFile(
     'wat-encrypted.data', 
     'wat-decrypted.jpg', 
     $key
 );
-
 $end_time = \microtime(true);
+
+if (!$success) {
+    echo 'File did not encrypt successfully.', "\n";
+    exit(1);
+}
 echo "wat-encrypted.data:\n\t";
-echo \number_format($end_time - $start_time, 2),
+echo \number_format($end_time - $start_time, 4),
     's (Memory: ', \number_format(\memory_get_usage() / 1024, 2), ' KB)',
     "\n";
-$end_time = $start_time;
 
-\Defuse\Crypto\File::decryptFile(
+$start_time = \microtime(true);
+$success = \Defuse\Crypto\File::decryptFile(
     'large.data',
     'large-decrypted.jpg', 
     $key
 );
-
 $end_time = \microtime(true);
+
+if (!$success) {
+    echo 'File did not encrypt successfully.', "\n";
+    exit(1);
+}
 echo "large.data:\n\t";
-echo \number_format($end_time - $start_time, 2),
+echo \number_format($end_time - $start_time, 4),
     's (Memory: ', \number_format(\memory_get_usage() / 1024, 2), ' KB)',
     "\n";
-$end_time = $start_time;
 
 if (\file_exists('In_the_Conservatory.jpg')) {
-    \Defuse\Crypto\File::encryptFile(
+    $start_time = \microtime(true);
+    $success = \Defuse\Crypto\File::encryptFile(
         'In_the_Conservatory.data',
         'In_the_Conservatory_decrypted.jpg',
         $key
     );
-    
     $end_time = \microtime(true);
+    
+    if (!$success) {
+        echo 'File did not encrypt successfully.', "\n";
+        exit(1);
+    }
     echo "In_the_Conservatory.data:\n\t";
-    echo \number_format($end_time - $start_time, 2),
+    echo \number_format($end_time - $start_time, 4),
         's (Memory: ', \number_format(\memory_get_usage() / 1024, 2), ' KB)',
         "\n";
     $end_time = $start_time;
diff --git a/test/stream/encrypt.php b/test/stream/encrypt.php
index 467b994..b07cfb2 100644
--- a/test/stream/encrypt.php
+++ b/test/stream/encrypt.php
@@ -8,54 +8,67 @@
 
 $mem = 0;
 $start_time = $end_time = \microtime(true);
-$key = \Defuse\Crypto\Encoding::hexToBin(\file_get_contents('key.txt'));
+$key = \Defuse\Crypto\Key::LoadFromAsciiSafeString(\file_get_contents('key.txt'));
+$end_time = \microtime(true);
 
 echo 'Encrypting', "\n", str_repeat('-', 50), "\n\n";
 echo "Load Key:\n\t";
 
-echo \number_format($end_time - $start_time, 2),
+echo \number_format($end_time - $start_time, 4),
     's (Memory: ', \number_format(\memory_get_usage() / 1024, 2), ' KB)',
     "\n";
-$end_time = $start_time;
 
-\Defuse\Crypto\File::encryptFile(
+$start_time = \microtime(true);
+$success = \Defuse\Crypto\File::encryptFile(
     'wat-gigantic-duck.jpg', 
     'wat-encrypted.data', 
     $key
 );
-
 $end_time = \microtime(true);
+
+if (!$success) {
+    echo 'File did not encrypt successfully.', "\n";
+    exit(1);
+}
 echo "wat-gigantic-duck.jpg:\n\t";
 
-echo \number_format($end_time - $start_time, 2),
+echo \number_format($end_time - $start_time, 4),
     's (Memory: ', \number_format(\memory_get_usage() / 1024, 2), ' KB)',
     "\n";
-$end_time = $start_time;
 
-\Defuse\Crypto\File::encryptFile(
+$start_time = \microtime(true);
+$success = \Defuse\Crypto\File::encryptFile(
     'large.jpg',
     'large.data',
     $key
 );
 $end_time = \microtime(true);
+
+if (!$success) {
+    echo 'File did not encrypt successfully.', "\n";
+    exit(1);
+}
 echo "large.jpg:\n\t";
-echo \number_format($end_time - $start_time, 2),
+echo \number_format($end_time - $start_time, 4),
     's (Memory: ', \number_format(\memory_get_usage() / 1024, 2), ' KB)',
     "\n";
-$end_time = $start_time;
 
 if (\file_exists('In_the_Conservatory.jpg')) {
-    \Defuse\Crypto\File::encryptFile(
+    $start_time = \microtime(true);
+    $success = \Defuse\Crypto\File::encryptFile(
         'In_the_Conservatory.jpg',
         'In_the_Conservatory.data',
         $key
     );
     $end_time = \microtime(true);
+    if (!$success) {
+        echo 'File did not encrypt successfully.', "\n";
+        exit(1);
+    }
     echo "In_the_Conservatory.jpg:\n\t";
-    echo \number_format($end_time - $start_time, 2),
+    echo \number_format($end_time - $start_time, 4),
         's (Memory: ', \number_format(\memory_get_usage() / 1024, 2), ' KB)',
         "\n";
-    $end_time = $start_time;
 }
 
 echo 'Peak Memory: ', \number_format(\memory_get_peak_usage() / 1048576, 2), ' MB', "\n\n";
diff --git a/test/stream/error.php b/test/stream/error.php
index 31bcc0b..74aa5b9 100644
--- a/test/stream/error.php
+++ b/test/stream/error.php
@@ -1,7 +1,7 @@
 <?php
 require_once \dirname(__DIR__).'/autoload.php';
 
-$key = base64_decode(file_get_contents('key.txt'));
+$key = \Defuse\Crypto\Key::LoadFromAsciiSafeString(\file_get_contents('key.txt'));
 
 echo 'Buffers: ', \Defuse\Crypto\File::BUFFER, "\n";
 echo microtime(true), "\n";
@@ -31,7 +31,7 @@
 fclose($ofp);
 
 \Defuse\Crypto\File::decryptFile(
-    'damaged.data', 
-    'wat-damaged.jpg', 
+    'damaged.data',
+    'wat-damaged.jpg',
     $key
 );
diff --git a/test/stream/keygen.php b/test/stream/keygen.php
index 098f05c..62e69df 100644
--- a/test/stream/keygen.php
+++ b/test/stream/keygen.php
@@ -3,4 +3,4 @@
 
 $key = \Defuse\Crypto\Crypto::createNewRandomKey();
 
-\file_put_contents('key.txt', \Defuse\Crypto\Encoding::binToHex($key->getRawBytes()));
+\file_put_contents('key.txt', $key->saveToAsciiSafeString());