diff --git a/hostkey.ser b/hostkey.ser
new file mode 100644
index 0000000..fb53aca
Binary files /dev/null and b/hostkey.ser differ
diff --git a/src/main/java/perfix/MethodInvocation.java b/src/main/java/perfix/MethodInvocation.java
new file mode 100644
index 0000000..2dea77d
--- /dev/null
+++ b/src/main/java/perfix/MethodInvocation.java
@@ -0,0 +1,29 @@
+package perfix;
+
+public class MethodInvocation {
+    private final long t0;
+    private final String name;
+    private long t1;
+
+    private MethodInvocation(String name) {
+        t0 = System.nanoTime();
+        this.name = name;
+    }
+
+    public static MethodInvocation start(String name) {
+        return new MethodInvocation(name);
+    }
+
+    public void stop() {
+        t1 = System.nanoTime();
+        Registry.add(this);
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    long getDuration() {
+        return t1 - t0;
+    }
+}