Add Nextcloud application

1 files changed, 86 insertions, 0 deletions

diff --git a/lib/Entropy/Entropy.php b/lib/Entropy/Entropy.php
new file mode 100644
index 0000000..36fde3c
--- /dev/null
+++ b/lib/Entropy/Entropy.php
@@ -0,0 +1,86 @@
+<?php
+
+/**
+ * @copyright Copyright (c) 2017 Matthias Held <matthias.held@uni-konstanz.de>
+ * @author Matthias Held <matthias.held@uni-konstanz.de>
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+namespace OCA\RansomwareDetection\Entropy;
+
+use OCP\ILogger;
+
+class Entropy
+{
+    /** @var ILogger */
+    private $logger;
+
+    /**
+     * @param IConfig $config
+     */
+    public function __construct(
+        ILogger $logger
+    ) {
+        $this->logger = $logger;
+    }
+
+    /**
+     * Calculates the entropy of data.
+     *
+     * @param string $data
+     *
+     * @return float
+     */
+    public function calculateEntropy($data)
+    {
+        $entropy = 0;
+        $size = strlen($data);
+
+        foreach (count_chars($data, 1) as $value) {
+            $p = $value / $size;
+            $entropy -= $p * log($p) / log(2);
+        }
+
+        return $entropy;
+    }
+
+    /**
+     * Calculates the standard deviation.
+     *
+     * @param array $array
+     *
+     * @return float
+     */
+    public function sd($array)
+    {
+        if (is_array($array) && count($array) > 0) {
+            // square root of sum of squares devided by N-1
+            return sqrt(array_sum(array_map(
+                function ($x, $mean) {
+                    return pow($x - $mean, 2);
+                },
+                $array,
+                array_fill(
+                    0,
+                    count($array),
+                (array_sum($array) / count($array))
+                )
+            )) / (count($array) - 1));
+        }
+
+        return 0.0;
+    }
+}