diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a09c56d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/.idea
diff --git a/entity/Letter.py b/entity/Letter.py
new file mode 100644
index 0000000..ced3545
--- /dev/null
+++ b/entity/Letter.py
@@ -0,0 +1,10 @@
+class Letter:
+    sign = ""
+    encryptType = "SM4-GCM"
+    encryptKey = ""
+    recvPubKey = ""
+    senderPubKey = ""
+
+    fileName = ""
+    fileSize = 0
+    fileBase64 = ""
diff --git a/main.py b/main.py
new file mode 100644
index 0000000..e69de29
diff --git a/recv/recv.py b/recv/recv.py
new file mode 100644
index 0000000..e69de29
diff --git a/sender/sender.py b/sender/sender.py
new file mode 100644
index 0000000..e69de29
diff --git a/tool/asymmetric/RSA.py b/tool/asymmetric/RSA.py
new file mode 100644
index 0000000..e69de29
diff --git a/tool/hash/sha.py b/tool/hash/sha.py
new file mode 100644
index 0000000..15ff5f5
--- /dev/null
+++ b/tool/hash/sha.py
@@ -0,0 +1 @@
+# sha-256
diff --git a/tool/symmetric/AES.py b/tool/symmetric/AES.py
new file mode 100644
index 0000000..e69de29
diff --git a/tool/symmetric/SM4.py b/tool/symmetric/SM4.py
new file mode 100644
index 0000000..e69de29