diff --git a/des.h b/des.h
new file mode 100644
index 0000000..2912ee0
--- /dev/null
+++ b/des.h
@@ -0,0 +1,75 @@
+#ifndef DES6_DES_H
+#define DES6_DES_H
+#include <iostream>
+#include "const.h"
+
+void createSubKey(const ull& key, ull* sub_key) {
+    ull pc1_out = calcPc1(key);
+    ull l = left28(pc1_out);
+    ull r = right28(pc1_out);
+    for (int i = 0; i < 6; i++) {
+        for (int j = 0; j < iteration_shift[i]; j++) {
+            l = (0x0fffffff & (l << 1)) | (0x00000001 & (l >> 27)); // left shift
+            r = (0x0fffffff & (r << 1)) | (0x00000001 & (r >> 27));
+        }
+        ull pc2_in = (l << 28) | r;
+        ull pc2_out = calcPc2(pc2_in);
+        sub_key[i] = pc2_out;
+    }
+}
+
+ull pre_l3 = 0;
+
+ull des(const ull& txt, const ull& key, bool encrypt) {
+    ull ip_out = calcIp(txt); // 初始置换
+    ull l = (ip_out >> 32) & ((1ULL << 32) - 1);
+    ull r = ip_out & ((1ULL << 32) - 1); // 分成左半部分和右半部分
+    ull sub_key[6];
+    createSubKey(key, sub_key); // 创建每一轮使用的子密钥
+    for (int i = 0; i < 6; i++) {
+        ull ext_out = calcExt(r); // 扩展
+        ull sbox_in;
+        if (encrypt) {
+            sbox_in = ext_out ^ sub_key[i];
+        }
+        else
+            sbox_in = ext_out ^ sub_key[5 - i];
+        ull sbox_out = calcSbox(sbox_in); // s盒
+        ull perm_out = calcPerm(sbox_out); // 置换
+
+        ull tmp = r;
+        r = l ^ perm_out;
+        l = tmp;
+
+        if (i == 2) {
+            pre_l3 ^= (l << 32) | r;
+        }
+    }
+    ull pi_in = l << 32 | r;
+    ull pi_out = calcPi(pi_in); // 末置换
+    return pi_out;
+}
+
+ull desEncrypt(const ull& txt, const ull& key) {
+    return des(txt, key, true);
+}
+
+ull desDecrypt(const ull& txt, const ull& key) {
+    return des(txt, key, false);
+}
+
+ull test() {
+
+    ull txtA = 14930861438147399743ULL;
+    ull keyA = 5123802368455698ULL;
+    ull outA = desEncrypt(txtA, keyA);
+
+    ull txtB = 10321427219600805951ULL;
+    ull outB = desEncrypt(txtB, keyA);
+
+    std::cout << outA << std::endl;
+    std::cout << outB << std::endl;
+}
+
+#endif //DES6_DES_H
+#pragma once