diff --git a/test/main.cxx b/test/main.cxx
index 64bcccc..b37f691 100644
--- a/test/main.cxx
+++ b/test/main.cxx
@@ -8,19 +8,20 @@ int main()
     uint8_t ik[32]{};
     hash(key.c_str(), ik);
 
+    int offset = 16;
     char* msg = new char[256]{};
     memset(msg, 0, 256);
-    auto len = std::snprintf(msg + 12, 256, "%s", "hello world");
-    std::cout << encrypt(ik, (uint8_t*)msg, len + 12) << std::endl;
-    std::cout << msg + 12 << std::endl;
+    auto len = std::snprintf(msg + offset, 256 - offset, "%s", "hello world");
+    std::cout << encrypt(ik, (uint8_t*)msg, len + offset) << std::endl;
+    std::cout << msg + offset << std::endl;
 
 
     uint8_t ik2[32]{};
     hash(key.c_str(), ik2);
 
-    std::cout << decrypt(ik2, (uint8_t*)msg, len + 12) << std::endl;
+    std::cout << decrypt(ik2, (uint8_t*)msg, len + offset) << std::endl;
 
-    std::cout << msg + 12 << std::endl;
+    std::cout << msg + offset << std::endl;
 
     return 0;
 }
\ No newline at end of file
diff --git a/util/util.cpp b/util/util.cpp
index d3268cb..93ce139 100644
--- a/util/util.cpp
+++ b/util/util.cpp
@@ -8,7 +8,7 @@
 #include <thread>
 
 CTransProtocal::CTransProtocal() = default;
-constexpr uint8_t kz = 12;
+constexpr uint8_t kz = 16;
 CTransProtocal::~CTransProtocal() = default;
 
 /*
@@ -309,7 +309,7 @@ bool encrypt(const uint8_t* k, uint8_t* m, size_t len)
     }
 
     uint8_t nonce[kz]{};
-    rdm(nonce, sizeof(nonce));
+    rdm(nonce, sizeof(nonce) - 4);
     memcpy(m, nonce, kz);
 
     struct AES_ctx ctx;