diff --git a/sheet02/a1/b.txt b/sheet02/a1/b.txt
new file mode 100644
index 0000000..e69de29
diff --git a/sheet02/a1/c.txt b/sheet02/a1/c.txt
new file mode 100644
index 0000000..e69de29
diff --git a/sheet02/a1/d.txt b/sheet02/a1/d.txt
new file mode 100644
index 0000000..e69de29
diff --git a/sheet02/a1/e.txt b/sheet02/a1/e.txt
new file mode 100644
index 0000000..e69de29
diff --git a/sheet02/a1/plaintext.txt b/sheet02/a1/plaintext.txt
new file mode 100644
index 0000000..e69de29
diff --git a/sheet02/a2/SignECDSA.java b/sheet02/a2/SignECDSA.java
new file mode 100644
index 0000000..3e53b75
--- /dev/null
+++ b/sheet02/a2/SignECDSA.java
@@ -0,0 +1,5 @@
+package sheet02.a2;
+
+public class SignECDSA {
+    
+}
diff --git a/sheet02/a2/VerifyECDSA.java b/sheet02/a2/VerifyECDSA.java
new file mode 100644
index 0000000..c772ace
--- /dev/null
+++ b/sheet02/a2/VerifyECDSA.java
@@ -0,0 +1,5 @@
+package sheet02.a2;
+
+public class VerifyECDSA {
+    
+}
diff --git a/sheet02/a2/c.txt b/sheet02/a2/c.txt
new file mode 100644
index 0000000..e69de29