diff --git a/lib/EAPBase/include/Config.h b/lib/EAPBase/include/Config.h
index 85360ad..c0d093e 100644
--- a/lib/EAPBase/include/Config.h
+++ b/lib/EAPBase/include/Config.h
@@ -53,7 +53,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     Configuration to pack
     ///
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const eap::config &val);
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const eap::config &val);
 
     ///
     /// Returns packed size of a configuration
@@ -70,7 +70,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     Configuration to unpack to
     ///
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ eap::config &val);
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ eap::config &val);
 }
 
 #pragma once
@@ -181,7 +181,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void pack(_Inout_ unsigned char *&cursor) const;
+        virtual void pack(_Inout_ eapserial::cursor_out &cursor) const;
 
         ///
         /// Returns packed size of a configuration
@@ -195,7 +195,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void unpack(_Inout_ const unsigned char *&cursor);
+        virtual void unpack(_Inout_ eapserial::cursor_in &cursor);
 
         /// @}
 
@@ -288,7 +288,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void pack(_Inout_ unsigned char *&cursor) const;
+        virtual void pack(_Inout_ eapserial::cursor_out &cursor) const;
 
         ///
         /// Returns packed size of a configuration
@@ -302,7 +302,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void unpack(_Inout_ const unsigned char *&cursor);
+        virtual void unpack(_Inout_ eapserial::cursor_in &cursor);
 
         /// @}
 
@@ -412,7 +412,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void pack(_Inout_ unsigned char *&cursor) const;
+        virtual void pack(_Inout_ eapserial::cursor_out &cursor) const;
 
         ///
         /// Returns packed size of a configuration
@@ -426,7 +426,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void unpack(_Inout_ const unsigned char *&cursor);
+        virtual void unpack(_Inout_ eapserial::cursor_in &cursor);
 
         /// @}
 
@@ -531,7 +531,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void pack(_Inout_ unsigned char *&cursor) const;
+        virtual void pack(_Inout_ eapserial::cursor_out &cursor) const;
 
         ///
         /// Returns packed size of a configuration
@@ -545,7 +545,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void unpack(_Inout_ const unsigned char *&cursor);
+        virtual void unpack(_Inout_ eapserial::cursor_in &cursor);
 
         /// @}
 
@@ -557,7 +557,7 @@ namespace eap
 
 namespace eapserial
 {
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const eap::config &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const eap::config &val)
     {
         val.pack(cursor);
     }
@@ -569,7 +569,7 @@ namespace eapserial
     }
 
 
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ eap::config &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ eap::config &val)
     {
         val.unpack(cursor);
     }
diff --git a/lib/EAPBase/include/Credentials.h b/lib/EAPBase/include/Credentials.h
index 91f88ed..d1047b7 100644
--- a/lib/EAPBase/include/Credentials.h
+++ b/lib/EAPBase/include/Credentials.h
@@ -293,7 +293,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void pack(_Inout_ unsigned char *&cursor) const;
+        virtual void pack(_Inout_ eapserial::cursor_out &cursor) const;
 
         ///
         /// Returns packed size of a configuration
@@ -307,7 +307,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void unpack(_Inout_ const unsigned char *&cursor);
+        virtual void unpack(_Inout_ eapserial::cursor_in &cursor);
 
         /// @}
 
diff --git a/lib/EAPBase/include/EAP.h b/lib/EAPBase/include/EAP.h
index 454508f..1ced4e7 100644
--- a/lib/EAPBase/include/EAP.h
+++ b/lib/EAPBase/include/EAP.h
@@ -48,13 +48,23 @@ namespace eap
 
 namespace eapserial
 {
+    ///
+    /// Output BLOB cursor
+    ///
+    struct cursor_out;
+
+    ///
+    /// Input BLOB cursor
+    ///
+    struct cursor_in;
+
     ///
     /// Packs a boolean
     ///
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     Variable with data to pack
     ///
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const bool &val);
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const bool &val);
 
     ///
     /// Returns packed size of a boolean
@@ -71,7 +81,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     Variable to receive unpacked value
     ///
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ bool &val);
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ bool &val);
 
     ///
     /// Packs a byte
@@ -79,7 +89,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     Variable with data to pack
     ///
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const unsigned char &val);
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const unsigned char &val);
 
     ///
     /// Returns packed size of a byte
@@ -96,7 +106,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     Variable to receive unpacked value
     ///
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ unsigned char &val);
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ unsigned char &val);
 
     ///
     /// Packs an unsigned int
@@ -104,7 +114,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     Variable with data to pack
     ///
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const unsigned int &val);
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const unsigned int &val);
 
     ///
     /// Returns packed size of an unsigned int
@@ -121,7 +131,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     Variable to receive unpacked value
     ///
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ unsigned int &val);
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ unsigned int &val);
 
 #ifdef _WIN64
     ///
@@ -130,7 +140,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     Variable with data to pack
     ///
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const size_t &val);
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const size_t &val);
 
     ///
     /// Returns packed size of a size_t
@@ -147,7 +157,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     Variable to receive unpacked value
     ///
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ size_t &val);
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ size_t &val);
 #endif
 
     ///
@@ -156,7 +166,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     String to pack
     ///
-    template<class _Elem, class _Traits, class _Ax> inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::basic_string<_Elem, _Traits, _Ax> &val);
+    template<class _Elem, class _Traits, class _Ax> inline void pack(_Inout_ cursor_out &cursor, _In_ const std::basic_string<_Elem, _Traits, _Ax> &val);
 
     ///
     /// Returns packed size of a string
@@ -173,7 +183,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     String to unpack to
     ///
-    template<class _Elem, class _Traits, class _Ax> inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ std::basic_string<_Elem, _Traits, _Ax> &val);
+    template<class _Elem, class _Traits, class _Ax> inline void unpack(_Inout_ cursor_in &cursor, _Out_ std::basic_string<_Elem, _Traits, _Ax> &val);
 
     ///
     /// Packs a wide string
@@ -181,7 +191,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     String to pack
     ///
-    template<class _Traits, class _Ax> inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::basic_string<wchar_t, _Traits, _Ax> &val);
+    template<class _Traits, class _Ax> inline void pack(_Inout_ cursor_out &cursor, _In_ const std::basic_string<wchar_t, _Traits, _Ax> &val);
 
     ///
     /// Returns packed size of a wide string
@@ -198,7 +208,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     String to unpack to
     ///
-    template<class _Traits, class _Ax> inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ std::basic_string<wchar_t, _Traits, _Ax> &val);
+    template<class _Traits, class _Ax> inline void unpack(_Inout_ cursor_in &cursor, _Out_ std::basic_string<wchar_t, _Traits, _Ax> &val);
 
     ///
     /// Packs a vector
@@ -206,7 +216,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     Vector to pack
     ///
-    template<class _Ty, class _Ax> inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::vector<_Ty, _Ax> &val);
+    template<class _Ty, class _Ax> inline void pack(_Inout_ cursor_out &cursor, _In_ const std::vector<_Ty, _Ax> &val);
 
     ///
     /// Returns packed size of a vector
@@ -223,7 +233,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     Vector to unpack to
     ///
-    template<class _Ty, class _Ax> inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ std::vector<_Ty, _Ax> &val);
+    template<class _Ty, class _Ax> inline void unpack(_Inout_ cursor_in &cursor, _Out_ std::vector<_Ty, _Ax> &val);
 
     ///
     /// Packs a list
@@ -231,7 +241,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     List to pack
     ///
-    template<class _Ty, class _Ax> inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::list<_Ty, _Ax> &val);
+    template<class _Ty, class _Ax> inline void pack(_Inout_ cursor_out &cursor, _In_ const std::list<_Ty, _Ax> &val);
 
     ///
     /// Returns packed size of a list
@@ -248,7 +258,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     List to unpack to
     ///
-    template<class _Ty, class _Ax> inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ std::list<_Ty, _Ax> &val);
+    template<class _Ty, class _Ax> inline void unpack(_Inout_ cursor_in &cursor, _Out_ std::list<_Ty, _Ax> &val);
 
     ///
     /// Packs a std::unique_ptr
@@ -256,7 +266,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     std::unique_ptr to pack
     ///
-    template<class _Ty, class _Dx> inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::unique_ptr<_Ty, _Dx> &val);
+    template<class _Ty, class _Dx> inline void pack(_Inout_ cursor_out &cursor, _In_ const std::unique_ptr<_Ty, _Dx> &val);
 
     ///
     /// Returns packed size of a std::unique_ptr
@@ -275,7 +285,7 @@ namespace eapserial
     ///// \param[inout] cursor  Memory cursor
     ///// \param[out]   val     std::unique_ptr to unpack to
     /////
-    //template<class _Ty, class _Dx> inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ std::unique_ptr<_Ty, _Dx> &val);
+    //template<class _Ty, class _Dx> inline void unpack(_Inout_ cursor_in &cursor, _Out_ std::unique_ptr<_Ty, _Dx> &val);
 
     ///
     /// Packs a certificate context
@@ -283,7 +293,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     Certificate context to pack
     ///
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const winstd::cert_context &val);
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const winstd::cert_context &val);
 
     ///
     /// Returns packed size of a certificate context
@@ -300,7 +310,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     Certificate context to unpack to
     ///
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ winstd::cert_context &val);
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ winstd::cert_context &val);
 
     ///
     /// Packs an EAP method type
@@ -308,7 +318,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[in]    val     EAP method type to pack
     ///
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const eap::type_t &val);
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const eap::type_t &val);
 
     ///
     /// Returns packed size of an EAP method type
@@ -325,7 +335,7 @@ namespace eapserial
     /// \param[inout] cursor  Memory cursor
     /// \param[out]   val     EAP method type to unpack to
     ///
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ eap::type_t &val);
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ eap::type_t &val);
 }
 
 #pragma once
@@ -346,10 +356,29 @@ namespace eap
 
 namespace eapserial
 {
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const bool &val)
+    struct cursor_out
     {
-        *cursor = val ? 1 : 0;
-        cursor++;
+        typedef unsigned char *ptr_type;
+
+        ptr_type ptr;       ///< Pointer to first data unwritten
+        ptr_type ptr_end;   ///< Pointer to the end of available memory
+    };
+
+    struct cursor_in
+    {
+        typedef const unsigned char *ptr_type;
+
+        ptr_type ptr;       ///< Pointer to first data unread
+        ptr_type ptr_end;   ///< Pointer to the end of BLOB
+    };
+
+
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const bool &val)
+    {
+        cursor_out::ptr_type ptr_end = cursor.ptr + 1;
+        assert(ptr_end <= cursor.ptr_end);
+        *cursor.ptr = val ? 1 : 0;
+        cursor.ptr = ptr_end;
     }
 
 
@@ -360,17 +389,21 @@ namespace eapserial
     }
 
 
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ bool &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ bool &val)
     {
-        val = *cursor ? true : false;
-        cursor++;
+        cursor_in::ptr_type ptr_end = cursor.ptr + 1;
+        assert(ptr_end <= cursor.ptr_end);
+        val = *cursor.ptr ? true : false;
+        cursor.ptr = ptr_end;
     }
 
 
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const unsigned char &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const unsigned char &val)
     {
-        *cursor = val;
-        cursor++;
+        cursor_out::ptr_type ptr_end = cursor.ptr + 1;
+        assert(ptr_end <= cursor.ptr_end);
+        *cursor.ptr = val;
+        cursor.ptr = ptr_end;
     }
 
 
@@ -381,17 +414,21 @@ namespace eapserial
     }
 
 
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ unsigned char &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ unsigned char &val)
     {
-        val = *cursor;
-        cursor++;
+        cursor_in::ptr_type ptr_end = cursor.ptr + 1;
+        assert(ptr_end <= cursor.ptr_end);
+        val = *cursor.ptr;
+        cursor.ptr = ptr_end;
     }
 
 
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const unsigned int &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const unsigned int &val)
     {
-        *(unsigned int*)cursor = val;
-        cursor += sizeof(unsigned int);
+        cursor_out::ptr_type ptr_end = cursor.ptr + sizeof(unsigned int);
+        assert(ptr_end <= cursor.ptr_end);
+        *(unsigned int*)cursor.ptr = val;
+        cursor.ptr = ptr_end;
     }
 
 
@@ -402,18 +439,22 @@ namespace eapserial
     }
 
 
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ unsigned int &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ unsigned int &val)
     {
-        val = *(unsigned int*)cursor;
-        cursor += sizeof(unsigned int);
+        cursor_in::ptr_type ptr_end = cursor.ptr + sizeof(unsigned int);
+        assert(ptr_end <= cursor.ptr_end);
+        val = *(unsigned int*)cursor.ptr;
+        cursor.ptr = ptr_end;
     }
 
 
 #ifdef _WIN64
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const size_t &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const size_t &val)
     {
-        *(size_t*)cursor = val;
-        cursor += sizeof(size_t);
+        cursor_out::ptr_type ptr_end = cursor.ptr + sizeof(size_t);
+        assert(ptr_end <= cursor.ptr_end);
+        *(size_t*)cursor.ptr = val;
+        cursor.ptr = ptr_end;
     }
 
 
@@ -424,22 +465,26 @@ namespace eapserial
     }
 
 
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ size_t &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ size_t &val)
     {
-        val = *(size_t*)cursor;
-        cursor += sizeof(size_t);
+        cursor_in::ptr_type ptr_end = cursor.ptr + sizeof(size_t);
+        assert(ptr_end <= cursor.ptr_end);
+        val = *(size_t*)cursor.ptr;
+        cursor.ptr = ptr_end;
     }
 #endif
 
 
     template<class _Elem, class _Traits, class _Ax>
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::basic_string<_Elem, _Traits, _Ax> &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const std::basic_string<_Elem, _Traits, _Ax> &val)
     {
         std::basic_string<_Elem, _Traits, _Ax>::size_type count = val.length();
-        assert(strlen(val.c_str()) == count); // String should not contain null characters
-        size_t nSize = sizeof(_Elem)*(count + 1);
-        memcpy(cursor, (const _Elem*)val.c_str(), nSize);
-        cursor += nSize;
+        assert(strlen(val.c_str()) == count); // String should not contain zero terminators.
+        size_t size = sizeof(_Elem)*(count + 1);
+        cursor_out::ptr_type ptr_end = cursor.ptr + size;
+        assert(ptr_end <= cursor.ptr_end);
+        memcpy(cursor.ptr, (const _Elem*)val.c_str(), size);
+        cursor.ptr = ptr_end;
     }
 
 
@@ -451,16 +496,18 @@ namespace eapserial
 
 
     template<class _Elem, class _Traits, class _Ax>
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ std::basic_string<_Elem, _Traits, _Ax> &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ std::basic_string<_Elem, _Traits, _Ax> &val)
     {
-        std::basic_string<_Elem, _Traits, _Ax>::size_type count = strlen((const _Elem*&)cursor);
-        val.assign((const _Elem*&)cursor, count);
-        cursor += sizeof(_Elem)*(count + 1);
+        size_t count_max = cursor.ptr_end - cursor.ptr;
+        std::basic_string<_Elem, _Traits, _Ax>::size_type count = strnlen((const _Elem*&)cursor.ptr, count_max);
+        assert(count < count_max); // String should be zero terminated.
+        val.assign((const _Elem*&)cursor.ptr, count);
+        cursor.ptr += sizeof(_Elem)*(count + 1);
     }
 
 
     template<class _Traits, class _Ax>
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::basic_string<wchar_t, _Traits, _Ax> &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const std::basic_string<wchar_t, _Traits, _Ax> &val)
     {
         std::string val_utf8;
         WideCharToMultiByte(CP_UTF8, 0, val.c_str(), (int)val.length(), val_utf8, NULL, NULL);
@@ -471,12 +518,12 @@ namespace eapserial
     template<class _Traits, class _Ax>
     inline size_t get_pk_size(const std::basic_string<wchar_t, _Traits, _Ax> &val)
     {
-        return sizeof(std::string::size_type) + WideCharToMultiByte(CP_UTF8, 0, val.c_str(), (int)val.length(), NULL, 0, NULL, NULL);
+        return sizeof(char)*(WideCharToMultiByte(CP_UTF8, 0, val.c_str(), (int)val.length(), NULL, 0, NULL, NULL) + 1);
     }
 
 
     template<class _Traits, class _Ax>
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ std::basic_string<wchar_t, _Traits, _Ax> &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ std::basic_string<wchar_t, _Traits, _Ax> &val)
     {
         std::string val_utf8;
         unpack(cursor, val_utf8);
@@ -485,7 +532,7 @@ namespace eapserial
 
 
     template<class _Ty, class _Ax>
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::vector<_Ty, _Ax> &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const std::vector<_Ty, _Ax> &val)
     {
         std::vector<_Ty, _Ax>::size_type count = val.size();
         pack(cursor, count);
@@ -511,7 +558,7 @@ namespace eapserial
 
 
     template<class _Ty, class _Ax>
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ std::vector<_Ty, _Ax> &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ std::vector<_Ty, _Ax> &val)
     {
         std::vector<_Ty, _Ax>::size_type count;
         unpack(cursor, count);
@@ -529,7 +576,7 @@ namespace eapserial
 
 
     template<class _Ty, class _Ax>
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::list<_Ty, _Ax> &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const std::list<_Ty, _Ax> &val)
     {
         std::list<_Ty, _Ax>::size_type count = val.size();
         pack(cursor, count);
@@ -555,7 +602,7 @@ namespace eapserial
 
 
     template<class _Ty, class _Ax>
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ std::list<_Ty, _Ax> &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ std::list<_Ty, _Ax> &val)
     {
         std::list<_Ty, _Ax>::size_type count;
         unpack(cursor, count);
@@ -572,7 +619,7 @@ namespace eapserial
 
 
     template<class _Ty, class _Dx>
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const std::unique_ptr<_Ty, _Dx> &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const std::unique_ptr<_Ty, _Dx> &val)
     {
         if (val) {
             pack(cursor, true);
@@ -593,13 +640,15 @@ namespace eapserial
     }
 
 
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const winstd::cert_context &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const winstd::cert_context &val)
     {
         if (val) {
             pack(cursor, (unsigned int)val->dwCertEncodingType);
             pack(cursor, (unsigned int)val->cbCertEncoded     );
-            memcpy(cursor, val->pbCertEncoded, val->cbCertEncoded);
-            cursor += val->cbCertEncoded;
+            cursor_out::ptr_type ptr_end = cursor.ptr + val->cbCertEncoded;
+            assert(ptr_end <= cursor.ptr_end);
+            memcpy(cursor.ptr, val->pbCertEncoded, val->cbCertEncoded);
+            cursor.ptr = ptr_end;
         } else {
             pack(cursor, (unsigned int)0);
             pack(cursor, (unsigned int)0);
@@ -619,7 +668,7 @@ namespace eapserial
     }
 
 
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ winstd::cert_context &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ winstd::cert_context &val)
     {
         DWORD dwCertEncodingType;
         unpack(cursor, (unsigned int&)dwCertEncodingType);
@@ -628,14 +677,16 @@ namespace eapserial
         unpack(cursor, (unsigned int&)dwCertEncodedSize);
 
         if (dwCertEncodedSize) {
-            val.create(dwCertEncodingType, (BYTE*)cursor, dwCertEncodedSize);
-            cursor += dwCertEncodedSize;
+            cursor_in::ptr_type ptr_end = cursor.ptr + dwCertEncodedSize;
+            assert(ptr_end <= cursor.ptr_end);
+            val.create(dwCertEncodingType, (BYTE*)cursor.ptr, dwCertEncodedSize);
+            cursor.ptr = ptr_end;
         } else
             val.free();
     }
 
 
-    inline void pack(_Inout_ unsigned char *&cursor, _In_ const eap::type_t &val)
+    inline void pack(_Inout_ cursor_out &cursor, _In_ const eap::type_t &val)
     {
         pack(cursor, (unsigned char)val);
     }
@@ -647,7 +698,7 @@ namespace eapserial
     }
 
 
-    inline void unpack(_Inout_ const unsigned char *&cursor, _Out_ eap::type_t &val)
+    inline void unpack(_Inout_ cursor_in &cursor, _Out_ eap::type_t &val)
     {
         unsigned char t;
         unpack(cursor, t);
diff --git a/lib/EAPBase/include/Module.h b/lib/EAPBase/include/Module.h
index cc34a10..c16c834 100644
--- a/lib/EAPBase/include/Module.h
+++ b/lib/EAPBase/include/Module.h
@@ -561,15 +561,13 @@ namespace eap
             if (!decrypt_md5(cp, pDataIn, dwDataInSize, data, ppEapError))
                 return false;
 
-            const unsigned char *cursor = data.data();
+            eapserial::cursor_in cursor = { data.data(), data.data() + data.size() };
             eapserial::unpack(cursor, record);
-            assert(cursor - data.data() <= (ptrdiff_t)data.size());
 #else
             UNREFERENCED_PARAMETER(ppEapError);
 
-            const unsigned char *cursor = pDataIn;
+            eapserial::cursor_in cursor = { pDataIn, pDataIn + dwDataInSize };
             eapserial::unpack(cursor, record);
-            assert(cursor - pDataIn <= (ptrdiff_t)dwDataInSize);
 #endif
 
             return true;
@@ -601,9 +599,9 @@ namespace eap
             data.resize(eapserial::get_pk_size(record));
 
             // Pack to BLOB.
-            unsigned char *cursor = data.data();
+            eapserial::cursor_out cursor = { data.data(), data.data() + data.size() };
             eapserial::pack(cursor, record);
-            data.resize(cursor - data.data());
+            data.resize(cursor.ptr - &data.front());
 
             // Prepare cryptographics provider.
             winstd::crypt_prov cp;
@@ -639,9 +637,9 @@ namespace eap
             }
 
             // Pack to BLOB.
-            unsigned char *cursor = *ppDataOut;
+            eapserial::cursor_out cursor = { *ppDataOut, *ppDataOut + *pdwDataOutSize };
             eapserial::pack(cursor, record);
-            assert(cursor - *ppDataOut <= (ptrdiff_t)*pdwDataOutSize);
+            *pdwDataOutSize = cursor.ptr - *ppDataOut;
 #endif
 
             return true;
diff --git a/lib/EAPBase/src/Config.cpp b/lib/EAPBase/src/Config.cpp
index 6270ebe..48a774b 100644
--- a/lib/EAPBase/src/Config.cpp
+++ b/lib/EAPBase/src/Config.cpp
@@ -81,7 +81,7 @@ bool eap::config::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **ppEapErr
 }
 
 
-void eap::config::pack(_Inout_ unsigned char *&cursor) const
+void eap::config::pack(_Inout_ eapserial::cursor_out &cursor) const
 {
     UNREFERENCED_PARAMETER(cursor);
 }
@@ -93,7 +93,7 @@ size_t eap::config::get_pk_size() const
 }
 
 
-void eap::config::unpack(_Inout_ const unsigned char *&cursor)
+void eap::config::unpack(_Inout_ eapserial::cursor_in &cursor)
 {
     UNREFERENCED_PARAMETER(cursor);
 }
@@ -236,7 +236,7 @@ bool eap::config_method::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **p
 }
 
 
-void eap::config_method::pack(_Inout_ unsigned char *&cursor) const
+void eap::config_method::pack(_Inout_ eapserial::cursor_out &cursor) const
 {
     config::pack(cursor);
     eapserial::pack(cursor, m_allow_save        );
@@ -262,7 +262,7 @@ size_t eap::config_method::get_pk_size() const
 }
 
 
-void eap::config_method::unpack(_Inout_ const unsigned char *&cursor)
+void eap::config_method::unpack(_Inout_ eapserial::cursor_in &cursor)
 {
     config::unpack(cursor);
     eapserial::unpack(cursor, m_allow_save        );
@@ -590,7 +590,7 @@ bool eap::config_provider::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR *
 }
 
 
-void eap::config_provider::pack(_Inout_ unsigned char *&cursor) const
+void eap::config_provider::pack(_Inout_ eapserial::cursor_out &cursor) const
 {
     config::pack(cursor);
     eapserial::pack(cursor, m_read_only         );
@@ -623,7 +623,7 @@ size_t eap::config_provider::get_pk_size() const
 }
 
 
-void eap::config_provider::unpack(_Inout_ const unsigned char *&cursor)
+void eap::config_provider::unpack(_Inout_ eapserial::cursor_in &cursor)
 {
     config::unpack(cursor);
     eapserial::unpack(cursor, m_read_only         );
@@ -776,7 +776,7 @@ bool eap::config_providers::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR
 }
 
 
-void eap::config_providers::pack(_Inout_ unsigned char *&cursor) const
+void eap::config_providers::pack(_Inout_ eapserial::cursor_out &cursor) const
 {
     config::pack(cursor);
     eapserial::pack(cursor, m_providers);
@@ -791,7 +791,7 @@ size_t eap::config_providers::get_pk_size() const
 }
 
 
-void eap::config_providers::unpack(_Inout_ const unsigned char *&cursor)
+void eap::config_providers::unpack(_Inout_ eapserial::cursor_in &cursor)
 {
     config::unpack(cursor);
 
diff --git a/lib/EAPBase/src/Credentials.cpp b/lib/EAPBase/src/Credentials.cpp
index f8cdcf3..f3f8bdb 100644
--- a/lib/EAPBase/src/Credentials.cpp
+++ b/lib/EAPBase/src/Credentials.cpp
@@ -233,7 +233,7 @@ bool eap::credentials_pass::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR
 }
 
 
-void eap::credentials_pass::pack(_Inout_ unsigned char *&cursor) const
+void eap::credentials_pass::pack(_Inout_ eapserial::cursor_out &cursor) const
 {
     eap::credentials::pack(cursor);
     eapserial::pack(cursor, m_identity);
@@ -250,7 +250,7 @@ size_t eap::credentials_pass::get_pk_size() const
 }
 
 
-void eap::credentials_pass::unpack(_Inout_ const unsigned char *&cursor)
+void eap::credentials_pass::unpack(_Inout_ eapserial::cursor_in &cursor)
 {
     eap::credentials::unpack(cursor);
     eapserial::unpack(cursor, m_identity);
diff --git a/lib/TLS/include/Config.h b/lib/TLS/include/Config.h
index 1172a45..7461245 100644
--- a/lib/TLS/include/Config.h
+++ b/lib/TLS/include/Config.h
@@ -141,7 +141,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void pack(_Inout_ unsigned char *&cursor) const;
+        virtual void pack(_Inout_ eapserial::cursor_out &cursor) const;
 
         ///
         /// Returns packed size of a configuration
@@ -155,7 +155,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void unpack(_Inout_ const unsigned char *&cursor);
+        virtual void unpack(_Inout_ eapserial::cursor_in &cursor);
 
         /// @}
 
diff --git a/lib/TLS/include/Credentials.h b/lib/TLS/include/Credentials.h
index b625675..2ce71a5 100644
--- a/lib/TLS/include/Credentials.h
+++ b/lib/TLS/include/Credentials.h
@@ -137,7 +137,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void pack(_Inout_ unsigned char *&cursor) const;
+        virtual void pack(_Inout_ eapserial::cursor_out &cursor) const;
 
         ///
         /// Returns packed size of a configuration
@@ -151,7 +151,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void unpack(_Inout_ const unsigned char *&cursor);
+        virtual void unpack(_Inout_ eapserial::cursor_in &cursor);
 
         /// @}
 
diff --git a/lib/TLS/src/Config.cpp b/lib/TLS/src/Config.cpp
index c001d35..2d97cd1 100644
--- a/lib/TLS/src/Config.cpp
+++ b/lib/TLS/src/Config.cpp
@@ -256,7 +256,7 @@ bool eap::config_method_tls::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR
 }
 
 
-void eap::config_method_tls::pack(_Inout_ unsigned char *&cursor) const
+void eap::config_method_tls::pack(_Inout_ eapserial::cursor_out &cursor) const
 {
     eap::config_method::pack(cursor);
     eapserial::pack(cursor, m_trusted_root_ca);
@@ -273,7 +273,7 @@ size_t eap::config_method_tls::get_pk_size() const
 }
 
 
-void eap::config_method_tls::unpack(_Inout_ const unsigned char *&cursor)
+void eap::config_method_tls::unpack(_Inout_ eapserial::cursor_in &cursor)
 {
     eap::config_method::unpack(cursor);
     eapserial::unpack(cursor, m_trusted_root_ca);
diff --git a/lib/TLS/src/Credentials.cpp b/lib/TLS/src/Credentials.cpp
index 8acf5b4..10f7670 100644
--- a/lib/TLS/src/Credentials.cpp
+++ b/lib/TLS/src/Credentials.cpp
@@ -167,7 +167,7 @@ bool eap::credentials_tls::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR *
 }
 
 
-void eap::credentials_tls::pack(_Inout_ unsigned char *&cursor) const
+void eap::credentials_tls::pack(_Inout_ eapserial::cursor_out &cursor) const
 {
     eap::credentials::pack(cursor);
     eapserial::pack(cursor, m_cert);
@@ -182,7 +182,7 @@ size_t eap::credentials_tls::get_pk_size() const
 }
 
 
-void eap::credentials_tls::unpack(_Inout_ const unsigned char *&cursor)
+void eap::credentials_tls::unpack(_Inout_ eapserial::cursor_in &cursor)
 {
     eap::credentials::unpack(cursor);
     eapserial::unpack(cursor, m_cert);
diff --git a/lib/TTLS/include/Config.h b/lib/TTLS/include/Config.h
index 2094405..b4d1271 100644
--- a/lib/TTLS/include/Config.h
+++ b/lib/TTLS/include/Config.h
@@ -127,7 +127,7 @@ namespace eap {
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void pack(_Inout_ unsigned char *&cursor) const;
+        virtual void pack(_Inout_ eapserial::cursor_out &cursor) const;
 
         ///
         /// Returns packed size of a configuration
@@ -141,7 +141,7 @@ namespace eap {
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void unpack(_Inout_ const unsigned char *&cursor);
+        virtual void unpack(_Inout_ eapserial::cursor_in &cursor);
 
         ///
         /// Returns EAP method type of this configuration
diff --git a/lib/TTLS/include/Credentials.h b/lib/TTLS/include/Credentials.h
index 7ac9615..1824de1 100644
--- a/lib/TTLS/include/Credentials.h
+++ b/lib/TTLS/include/Credentials.h
@@ -133,7 +133,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void pack(_Inout_ unsigned char *&cursor) const;
+        virtual void pack(_Inout_ eapserial::cursor_out &cursor) const;
 
         ///
         /// Returns packed size of a configuration
@@ -147,7 +147,7 @@ namespace eap
         ///
         /// \param[inout] cursor  Memory cursor
         ///
-        virtual void unpack(_Inout_ const unsigned char *&cursor);
+        virtual void unpack(_Inout_ eapserial::cursor_in &cursor);
 
         /// \name Storage
         /// @{
diff --git a/lib/TTLS/src/Config.cpp b/lib/TTLS/src/Config.cpp
index 8aa5040..61aaaf5 100644
--- a/lib/TTLS/src/Config.cpp
+++ b/lib/TTLS/src/Config.cpp
@@ -158,7 +158,7 @@ bool eap::config_method_ttls::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERRO
 }
 
 
-void eap::config_method_ttls::pack(_Inout_ unsigned char *&cursor) const
+void eap::config_method_ttls::pack(_Inout_ eapserial::cursor_out &cursor) const
 {
     eap::config_method_tls::pack(cursor);
     if (m_inner) {
@@ -195,7 +195,7 @@ size_t eap::config_method_ttls::get_pk_size() const
 }
 
 
-void eap::config_method_ttls::unpack(_Inout_ const unsigned char *&cursor)
+void eap::config_method_ttls::unpack(_Inout_ eapserial::cursor_in &cursor)
 {
     eap::config_method_tls::unpack(cursor);
 
diff --git a/lib/TTLS/src/Credentials.cpp b/lib/TTLS/src/Credentials.cpp
index e9b5b79..741c8f8 100644
--- a/lib/TTLS/src/Credentials.cpp
+++ b/lib/TTLS/src/Credentials.cpp
@@ -149,7 +149,7 @@ bool eap::credentials_ttls::load(_In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR
 }
 
 
-void eap::credentials_ttls::pack(_Inout_ unsigned char *&cursor) const
+void eap::credentials_ttls::pack(_Inout_ eapserial::cursor_out &cursor) const
 {
     eap::credentials_tls::pack(cursor);
     if (m_inner) {
@@ -186,7 +186,7 @@ size_t eap::credentials_ttls::get_pk_size() const
 }
 
 
-void eap::credentials_ttls::unpack(_Inout_ const unsigned char *&cursor)
+void eap::credentials_ttls::unpack(_Inout_ eapserial::cursor_in &cursor)
 {
     eap::credentials_tls::unpack(cursor);