64-bit electronic key

Download source code - 88.1 KB

Introduction

In the article, I am going to demonstrate how to use Serial Number DS1990 from Dallas Semiconductor as an electronic key to obtain authorized access to an application. This will be the continuation of my article about 1-Wire technology, where I have described temperature measurement [1]. My first concept was to modify the gina.dll library which is used while logging in to Windows. But, as I saw it could cause a lot of problems for beginners and even lock access to the system, I decided to give up it. Nevertheless, for advanced users, I recommend reading [2], [3].

Why DS1990?

Fig. 1. DS1990 memory map [4]

DS1990 is a serial number [4] which contains a unique ROM number (Fig. 1). The number consists of an 8-bit CRC code, a 48-bit serial number, and an 8-bit family code. There are no identical ROM numbers in the world. The other advantages are: very long working life, it is cheap in comparison with transponders or other identity cards, the serial number could be checked because it contains a CRC code, it could be easily implemented in both PCs and microcontrollers.

Installation

To use this software, you will need:

DS9097E adapter, which was described in [1] (Fig. 2)
DS1990 serial key (Fig. 3)
iButton Probe DS9092 or its equivalent [5] (Fig. 4)

Fig. 2. DS9097E adapter [1]

Fig. 3. DS1990 serial key

Fig. 4. iButton probe

Using the code

#include <conio.h>
#include <stdio.h>
#include "onewire.h"

void main(int argc, char **argv)
{
    short* ROM = new short[8];
    COneWire key("IBFS32.DLL",OW_ADAPTER_DS9097E,1);
    short data[] = {'a','b','c','1','2','3'};

    if(!key.StartSession())
    {
        printf("%s\n",ErrorDescr(key.GetLastError()));
        exit(-1);
    }

    printf("Ready to read...\n");

    while(!_kbhit())
    {
        if(key.FindDevices() == 1)
        {
            key.GetRomCode(0,ROM);
            for(int i=0;i<8;i++)
                printf("%2X ",ROM[i]);
            printf("\n");
        }
        Sleep(10);
    }

    delete[] ROM;

    key.EndSession();
}

In a loop, I am checking whether the electronic key was touching the probe. If it was, I read the ROM and print it.

Conclusions

There are unlimited applications for DS1990 serial numbers. I hope you will have your own. And to conclude, you have to be conscious that some people have created emulators of DS1990 serial numbers, but do not worry: as long as the robber does not know your key number, you are safe. Also, if you lose your traditional key, everybody could make a copy of it.