diff --git a/libs/keyLib.php b/libs/keyLib.php
index 86ce0c9..a321677 100755
--- a/libs/keyLib.php
+++ b/libs/keyLib.php
@@ -87,6 +87,7 @@
 			return null;
 		$data = fread($handle, filesize($fileName));
 		$lines = explode("\n", $data);
+		fclose($handle);
 		$keyData = array();
 		for ($i = 1; $i < count($lines); $i++)
 		{
@@ -118,7 +119,11 @@
 		for ($i = 0; $i < $count; $i++)
 			$data = $data . $i . ";" . $keyData[$i][0] . ";" . $keyData[$i][1] . "\n";
 		$data = $data . $count . ";" . $keyData[$count][0] . ";" . $keyData[$count][1];
+
+		//use exclusive lock for writing
+		flock($handle, LOCK_EX);
 		$res = fwrite($handle, $data);
+		flock($handle, LOCK_UN);
 		// debug Code
 		//if ($res == false)
 		//	echo "<script type='text/javascript'>alert('file not written');</script>";
diff --git a/libs/loggingLib.php b/libs/loggingLib.php
index cfd3957..da5f4af 100755
--- a/libs/loggingLib.php
+++ b/libs/loggingLib.php
@@ -9,8 +9,8 @@
 //               and tutors.
 //============================================================================
 
-	define ("STUDENTLOGFILE", "logs/ESE2013_studentLog.txt");
-	define ("TUTORLOGFILE", "logs/ESE2013_tutorLog.txt");
+	define ("STUDENTLOGFILE", "logs/ESE_studentLog.txt");
+	define ("TUTORLOGFILE", "logs/ESE_tutorLog.txt");
 	
 	/**
 	 * Reads all question data out of a provided log file array that has been split by new lines.
@@ -178,6 +178,7 @@
 		// otherwise read the file and split the string at each new line
 		$fileData = fread($handle, $length);
 		$lines = explode("\n", $fileData);
+		fclose($handle);
 		// begin parsing of the file, the beginning is the second line, because the
 		// first should contains the disclaimer
 		$index = 1;
@@ -231,7 +232,10 @@
 			// each comment is escapd by a new line containing three tilde characters
 			$fileData = $fileData . "\n" . $comment . "\n~~~";
 		// write the generated data to the file and close it
+		// use exclusive lock
+		flock($handle, LOCK_EX);
 		fwrite($handle, $fileData);
+		flock($handle, LOCK_UN);
 		fclose($handle);
 		return true;
 	}
@@ -301,4 +305,4 @@
 		if (array_key_exists("comment", $formData) && trim($formData["comment"]) != "")
 			array_push($commentData, $formData["comment"]);
 	}
-?>
\ No newline at end of file
+?>