Like computers have become part and parcel of daily lives, the passwords have too. From operating systems to website logins, the most common and secured way to get access is the password protection. The passwords just serve like the keys. Like the keys open physical locks, the passwords open the digital locks for access to operating systems and other software or website. Generally users need to type the password in a textbox and press some button to get access to OS, software or website. While typing the password, it can be seen by an onlooker or tracked by key logging. This project is a USB device that will store the user passwords and print it out to a login window just by pressing a single button.
The project is an USB Plug and Play device that works like an automated keyboard thus saves the password being stolen by looking one type it or key logging software. The project has been built on Atmega 32u4 based Generic USB Keyboard project which was based on making a generic USB Keyboard.
Fig. 1: Prototype of Arduino Based USB Digital Password Generator
The project will be called password generator and it will store password and print it to a password box on pressing a single button. The project utilizes 8-bit USB AVR – Atmega 32u4 as the USB controller chip and uses AVR based Lightweight USB Framework (LUFA) as the firmware which is modified to retrieve password on USB.
The LUFA firmware is used and its HID device driver class for keyboard is modified to program the project. The firmware is modified to pre-store a password and automate the process of typing it. The device works with all the desktop and mobile operating systems and applications. It can also be used with any browser.
The project uses a tactile switch to receive call to action while Atmega 32u4 is the controller chip (on board Arduino Pro Micro) and USB cable is used to connect with the personal computer.
PREREQUISITES
This project is based on Arduino Pro Micro which has the USB AVR – Atmega 32u4 as the sitting MCU. In order to understand this project, one must have basic knowledge of the AVR microcontrollers and the embedded C programming for AVRs. WinAVR Studio is used to write, edit and compile the project code, so closely following the project shall require familiarizing with the above stated IDE as well. Though LUFA framework takes care of implementing the USB protocol and has APIs to abstract the lower level codes, understanding USB protocol is recommended to understand how actually the project is working. In fact, if anyone has already worked on some other microcontroller, it will not be much pain to understand and follow this project as the project code is more or less about getting input from the GPIO pins of AVR MCU and modifying the LUFA device driver of generic keyboard accordingly.
Fig. 2: Image showing Arduino based USB Digital Password Generator being used to login Facebook
COMPONENTS REQUIRED
1. Arduino Pro Micro
2. Breadboard
3. Connecting wires
4. Push button
5. Micro USB cable
6. 10K resistors
SOFTWARE TOOLS REQUIRED
1. WinAVR Studio
2. AVR Dude
3. LUFA Firmware
BLOCK DIAGRAM
Fig. 3: Block Diagram of Arduino Based USB Digital Password Generator
CIRCUIT CONNECTIONS
The project uses Arduino Pro Micro as the USB controller chip. There is a single tactile switch connected at the pin 5 of port B of the Arduino. The switch is provided to get the call to action that password has to be printed..
The tactile switch is connected between the port and ground. The pin 5 of port B by default is connected to VCC and receive a HIGH logic. Pressing the tactile switch changes the status at the respective pin to LOW by short circuiting to the ground.
The Program code for the project is burnt to the Arduino Pro Micro using AVR Dude. The Arduino board is connected to the USB port of a PC by a USB cable.
HOW THE PROJECT WORKS
For configuring the controller chip to work as an automated keyboard, the HID Class Driver for keyboard of the LUFA framework is used. The Human Interface Device (HID) class takes care of the transfers between the host device and the human controlled USB peripherals like USB Keyboard, Mouse or Joystick. The implementation of the USB protocol is carried out by the open-source drivers of the LUFA framework.
Like any HID device, when the digital password generator is attached to the host computer (PC), the host sends request for configuration details in the form of control transfer. The controller chip on the device has to respond with appropriate descriptors to get configured and ready for further operations. Only after configuration, the device can transfer password on user input with the host in the form of interrupt transfers. The process of identification and configuration of any USB device with the host is called enumeration.
Any device using HID class for keyboards identifies the key pressed by the keycode or combination of keycodes sent from the controller chip of the device to the host in the data input report. The device is basically an automated keyboard. Any keyboard device sends a usage report and data input report to the host and receives data output report from the host at the application layer to work like a keyboard. The reports are a medium at application layer as per the USB protocol to facilitate enumeration and communication between the host and the device. To learn about HID Class for Keyboard and how the usage report, data input report and data output report are structured in the HID Class for Keyboard, go through the Atmega 32u4 based Generic USB Keyboard project.To learn about the keycodes assigned to different ASCII characters and modifier keys on a generic keyboard, check out the HID Usage Table provided by the USB Implementers Forum.
The series of keycodes representing the password have to be passed to the host on pressing a single key. This is managed by the program code of USB controller chip. The password can consist of uppercase, lowercase letters, number or special characters (* # , / . A – @). The lowercase alphabets can be sent directly by sending the equivalent keycode in the Data input report but for Uppercase and Special symbols, the keycode for Shift key along with other keycode needs to be sent in the Data input report. After transmitting a keycode, an empty data report is sent to indicate that the key has been released. The empty data report is generally a NULL report. This means, after sending a keycode for a character every time a NULL report will have to be sent. This process continues until all keycodes for the required characters are transmitted. In a password box, the characters do not display but appear as a string of asterisk.
Fig. 4: Image showing Arduino based USB Digital Password Generator being used to login Facebook
This device is an automated keyboard. A keyboard is HID class USB device and LUFA framework has HID class related modules in the LUFA-Source-Folder /LUFA/Drivers/USB/Class/Device folder. Other device class related module are also in the same folder. The LUFA framework has demo projects for different USB device classes in the LUFA-Source-FolderDemosDeviceClassDriver folder. For implementing the project, demo project for keyboard provided in the LUFA framework is modified and complied. The demo project for keyboard is in the LUFA-Source-FolderDemosDeviceClassDriverKeyboard folder. The folder contains keyboard.c file which will be modified to work like an automated keyboard.
How Keyboard.c identifies HID device being Keyboard
The keyboard.c uses Keyboard_HID_Interface interface in HID_Device_USBTask() function which is being imported from the HIDDeviceClass.c (from LUFA-Source-Folder LUFADriversUSBClassDevice) to configure the device as keyboard. The interface abstracts the low-level descriptor codes and identifies the device as keyboard through an InterfaceNumber variable.
From Where Keyboard.C gets the USAGE and Data Reports Descriptors
In the LUFA framework’s demo project for Keyboard, descriptor.c file is imported in keyboard.c to send the relevant usage and data reports descriptors to the host device. The descriptor.c defines a KeyboardReport[] structure which is used in the CALLBACK_HID_Device_CreateHIDReport() function of the keyboard.c to generate keyboard specific usage and data reports descriptors. Inside descriptor.c the KeyboardReport[] structure has the values returned by HID_DESCRIPTOR_KEYBOARD () function. The HID_DESCRIPTOR_KEYBOARD() is defined in HIDClassCommon.h (located in LUFA-Source-FolderLUFADriversUSBClassCommon folder). The keyboard.c imports keyboard.h which imports usb.h. USB.h imports HIDCLass.h. In HIDClass.h is imported HIDClassDevice.h if the USB_CAN_BE_DEVICE is true for the controller chip to being an USB device not the host. The HIDClassDevice.h imports HIDClassCommon.h where the HID device specific descriptor fields have been defined.
HOW THE DEVICE WORKS
The AVR microcontroller is programmed to get the user input from the tactile switch that prompts the controller chip to transfer the password to the host. The main() function and CALLBACK_HID_Device_CreateHIDReport() function of the keyboard.c are modified to customize the program code to send the required keycodes or combination of keycodes in the data input reports. A series of data input reports along with null report after each data input report will be sent from the device. Check out the program code to see the modifications implemented for building the project.
Fig. 5: Image showing Arduino based USB Digital Password Generator being used to login Facebook
PROGRAMMING GUIDE
For building the project download the LUFA framework from the github.com. The demo project provided with the LUFA framework is modified to make the password generator. In the extracted LUFA zip file, open Demos/Device/ClassDriver/Keyboard folder. The folder has the following files and folders.
Fig. 6: Screenshot of LUFA Library Folder on Windows
Of these, Keyboard.h, Keyboard.c and Makefile needs to be modified for this project. The modified files (provided at the bottom of the article in zip format) can also be downloaded from the engineersgarage and replaced with the original files. Either open the files in WinAVR Studio or Notepad++ and modify original files or replace files with the already modified one. The modified or replaced Keyboard.c needs to be compiled from within the LUFA’s Source folder to get the object code.
Modifying Keyboard.h
The Keyboard.h library file is imported in the Keyboard.c file and includes a set of additional libraries and defines the constants and functions for the keyboard device. These include the additional libraries for the joystick, button and LEDs which should be commented out as the project is not using these HID features. So open Keyboard.h and make the following changes – :
• Comment the #include library statements for Joystick.h, LEDS.h, and Buttons.h (The include statements for these libraries are commented as any joystick, buttons board and LED board is not used in the project)
Save the file with changes
Modifying Keyboard.C file
Again in the Keyboard.c, the code sections for Joystick, button board and LEDs need to be commented out. So open Keyboard.c and make the following changes – :
• In the main loop, comment the LEDs_SetAllLEDs()
• In SetupHardware() function, comment the Joystick_Init(), LEDs_Init(), Buttons_Init()
• In EVENT_USB_Device_Connect() function, comment the LEDs_SetAllLEDs()
• In EVENT_USB_Device_Disconnect() function, comment LEDs_SetAllLEDs()
• In EVENT_USB_Device_ConfigurationChanged() function, comment the LEDs_SetAllLEDs()
In Keyboard.c the main() function executes the functioning of the password generator. Inside the main function, Port B where the tactile switch has been connected needs to be defined as input and the pin 5 of port B has to be raised to HIGH logic by default as the microcontroller will need to detect LOW logic for input from the tactile switch. Therefore, modify the body of main() function as the code given below.
Inside the infinite for loop the HID_Device_USBTask() function is called where Keyboard_HID_Interface interface is passed as parameter. The interface identifies the device as keyboard and abstracts the low level program code specific to keyboard HID class. The function is coming from the HIDClassDevice.c module (located in LUFA/Drivers/USB/Class/Device/HIDClassDevice.c) and is used for general management task for a given HID class interface, required for the correct operation of the interface. It should be called in the main program loop, before the master USB management task USB_USBTask(). The USB_USBTask() is the main USB management task. The USB driver requires this task to be executed continuously when the USB system is active (device attached in host mode, or attached to a host in device mode) in order to manage USB communications. The function is defined in USBTask.c (Located in LUFA-Source-FolderLUFADriversUSBCore folder).
For sending a series of Data Input reports including null report CALLBACK_HID_Device_CreateHIDReport() needs to be modified. The default file has the function body to detect joystick movement as well.
Fig. 7: Screenshot of CALLBACK_HID_Device_CreateHIDReport Function in LUFA Library
Remove the statements from body of CALLBACK_HID_Device_CreateHIDReport() function. Two Boolean variables to keep check the status of key being released or not and the another character ready to be sent or not are defined. The password is stored in an array – password[] and a counter variable is defined to run a loop. A loop is run by an if-else statement where the elements of password[] array are read to the length of the array and counter variable is increased. The character that has to be sent in an individual data input report is sent by ASCII to keycode conversion function with or without combination of shift modifier key. So replace the body of the CALLBACK_HID_Device_CreateHIDReport() function with the following code.
In the body _BV() function is used to map the respective bit as a byte with only the respective bit changed in the returned byte.
The Data Output Report is not utilized in the project execution therefore the CALLBACK_HID_Device_ProcessHIDReport() function which process Data Output report has been kept unchanged.
Save the file and create Make file for the project.
Modifying Make File
In the Keyboard folder there is a make file that needs to be edited. The file can be edited using Notepad++. The following information needs to be edited – :
• MCU = atmega32u4
Save the file and exit. Now all the files are edited completely for the Password Generator Project.
Compiling Keyboard.c
For compiling the source code, WinAVR Programmers Notepad or Arduino IDE can be used. Open the modified Keyboard.c file and compile the code.
BURNING HEX CODE
The hex file is generated on compiling the keyboard.c file. For burning the object code to microcontroller open the Command Prompt, change the current directory to the directory containing the Hex file. This can be done using command: CD <address of the directory>. Now reset the Arduino and instantly run the command: : avrdude -v -p atmega32u4 -c avr109 -P COM20 -b 57600 -D -Uflash:w:Keyboard.hex:i after replacing the COM Port with the recognized one.
If the uploading process is successful, the Arduino board will be shown as HID Keyboard in the Device Manager. There is no need of installing any driver in the computer as Generic HID Keyboard is used for the project implementation. Boot the operating system or the login window of any software or website and point the cursor to the password box. Now plug in the password generator and press button to print out the password. Click on the submit button to login the operating system, software or website. The password stored in the device can be changed by changing the content of password[] array in the program code..
In the next project – Atmega 32u4 based USB Number Pad, learn how to make a numeric keypad that can connect to any computer or computing device through USB.
Project Source Code
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/* LUFA Library Copyright (C) Dean Camera, 2015. dean [at] fourwalledcubicle [dot] com www.lufa-lib.org */ /* Copyright 2015 Dean Camera (dean [at] fourwalledcubicle [dot] com) Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that the copyright notice and this permission notice and warranty disclaimer appear in supporting documentation, and that the name of the author not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. The author disclaims all warranties with regard to this software, including all implied warranties of merchantability and fitness. In no event shall the author be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use or performance of this software. */ /** file * * Main source file for the Keyboard demo. This file contains the main tasks of * the demo and is responsible for the initial application hardware configuration. */ #include "Keyboard.h" /** Buffer to hold the previously generated Keyboard HID report, for comparison purposes inside the HID class driver. */ static uint8_t PrevKeyboardHIDReportBuffer[sizeof(USB_KeyboardReport_Data_t)]; /** LUFA HID Class driver interface configuration and state information. This structure is * passed to all HID Class driver functions, so that multiple instances of the same class * within a device can be differentiated from one another. */ USB_ClassInfo_HID_Device_t Keyboard_HID_Interface = { .Config = { .InterfaceNumber = INTERFACE_ID_Keyboard, .ReportINEndpoint = { .Address = KEYBOARD_EPADDR, .Size = KEYBOARD_EPSIZE, .Banks = 1, }, .PrevReportINBuffer = PrevKeyboardHIDReportBuffer, .PrevReportINBufferSize = sizeof(PrevKeyboardHIDReportBuffer), }, }; /** Main program entry point. This routine contains the overall program flow, including initial * setup of all components and the main program loop. */ uint8_t ASCII_to_keycode(char value) { if(value >= 'a' && value <= 'z') { return (4 + value - 'a'); // 4 is the keycode for ‘a’ } else if(value >= 'A' && value <= 'Z') { return (4 + value - 'A'); // 4 is the keycode for ‘a’ } else if(value >= '1' && value <= '9') { return (30 + value - '1'); // 30 is the key code for ‘1’ } else if(value == '0') return 39; // 39 is keycode for 0 else if(value == '*') return 37; // 37 is keycode for * else if(value == '#') return 32; // 32 is keycode for # // more conditions can be made for other ASCII codes return 0; } int main(void) { SetupHardware(); DDRB = 0x00; PORTB = 0xff; //LEDs_SetAllLEDs(LEDMASK_USB_NOTREADY); GlobalInterruptEnable(); for (;;) { HID_Device_USBTask(&Keyboard_HID_Interface); USB_USBTask(); } } /** Configures the board hardware and chip peripherals for the demo's functionality. */ void SetupHardware() { #if (ARCH == ARCH_AVR8) /* Disable watchdog if enabled by bootloader/fuses */ MCUSR &= ~(1 << WDRF); wdt_disable(); /* Disable clock division */ clock_prescale_set(clock_div_1); #elif (ARCH == ARCH_XMEGA) /* Start the PLL to multiply the 2MHz RC oscillator to 32MHz and switch the CPU core to run from it */ XMEGACLK_StartPLL(CLOCK_SRC_INT_RC2MHZ, 2000000, F_CPU); XMEGACLK_SetCPUClockSource(CLOCK_SRC_PLL); /* Start the 32MHz internal RC oscillator and start the DFLL to increase it to 48MHz using the USB SOF as a reference */ XMEGACLK_StartInternalOscillator(CLOCK_SRC_INT_RC32MHZ); XMEGACLK_StartDFLL(CLOCK_SRC_INT_RC32MHZ, DFLL_REF_INT_USBSOF, F_USB); PMIC.CTRL = PMIC_LOLVLEN_bm | PMIC_MEDLVLEN_bm | PMIC_HILVLEN_bm; #endif /* Hardware Initialization */ //Joystick_Init(); //LEDs_Init(); //Buttons_Init(); USB_Init(); } /** Event handler for the library USB Connection event. */ void EVENT_USB_Device_Connect(void) { //LEDs_SetAllLEDs(LEDMASK_USB_ENUMERATING); } /** Event handler for the library USB Disconnection event. */ void EVENT_USB_Device_Disconnect(void) { //LEDs_SetAllLEDs(LEDMASK_USB_NOTREADY); } /** Event handler for the library USB Configuration Changed event. */ void EVENT_USB_Device_ConfigurationChanged(void) { bool ConfigSuccess = true; ConfigSuccess &= HID_Device_ConfigureEndpoints(&Keyboard_HID_Interface); USB_Device_EnableSOFEvents(); //LEDs_SetAllLEDs(ConfigSuccess ? LEDMASK_USB_READY : LEDMASK_USB_ERROR); } /** Event handler for the library USB Control Request reception event. */ void EVENT_USB_Device_ControlRequest(void) { HID_Device_ProcessControlRequest(&Keyboard_HID_Interface); } /** Event handler for the USB device Start Of Frame event. */ void EVENT_USB_Device_StartOfFrame(void) { HID_Device_MillisecondElapsed(&Keyboard_HID_Interface); } /** HID class driver callback function for the creation of HID reports to the host. * * param[in] HIDInterfaceInfo Pointer to the HID class interface configuration structure being referenced * param[in,out] ReportID Report ID requested by the host if non-zero, otherwise callback should set to the generated report ID * param[in] ReportType Type of the report to create, either HID_REPORT_ITEM_In or HID_REPORT_ITEM_Feature * param[out] ReportData Pointer to a buffer where the created report should be stored * param[out] ReportSize Number of bytes written in the report (or zero if no report is to be sent) * * return Boolean c true to force the sending of the report, c false to let the library determine if it needs to be sent */ bool CALLBACK_HID_Device_CreateHIDReport(USB_ClassInfo_HID_Device_t* const HIDInterfaceInfo, uint8_t* const ReportID, const uint8_t ReportType, void* ReportData, uint16_t* const ReportSize) { USB_KeyboardReport_Data_t* KeyboardReport = (USB_KeyboardReport_Data_t*)ReportData; static bool key_status; // 0 means its time to send character, 1 means its time to break or send NULL static bool ready_to_send; // check to indicate that button is pressed or not char password[] = "*hI#"; // password declaration static int index_counter; // array index counter for keeping track of converting character if(!(PINB & _BV(5))) ready_to_send = 1;// button is pressed and ready to send if(ready_to_send) { if(key_status == 0) // send character { if(index_counter < strlen(password)) // send characters one by one until all are send { // convert ASCII character to keyboard keycode KeyboardReport->KeyCode[0] = ASCII_to_keycode(password[index_counter]); //if character was Uppercase Alphabet or special sign, send Shift key if(password[index_counter] >= 'A' && password[index_counter] <= 'Z' || password[index_counter] == '*' || password[index_counter] == '#') KeyboardReport->Modifier = HID_KEYBOARD_MODIFIER_LEFTSHIFT; index_counter = index_counter + 1;// increment counter for next character } key_status = 1; // to break or send NULL key next time } else key_status = 0; } *ReportSize = sizeof(USB_KeyboardReport_Data_t); return false; } /** HID class driver callback function for the processing of HID reports from the host. * * param[in] HIDInterfaceInfo Pointer to the HID class interface configuration structure being referenced * param[in] ReportID Report ID of the received report from the host * param[in] ReportType The type of report that the host has sent, either HID_REPORT_ITEM_Out or HID_REPORT_ITEM_Feature * param[in] ReportData Pointer to a buffer where the received report has been stored * param[in] ReportSize Size in bytes of the received HID report */ void CALLBACK_HID_Device_ProcessHIDReport(USB_ClassInfo_HID_Device_t* const HIDInterfaceInfo, const uint8_t ReportID, const uint8_t ReportType, const void* ReportData, const uint16_t ReportSize) { }###
Circuit Diagrams
Project Datasheet
https://www.engineersgarage.com/wp-content/uploads/2019/10/Password-Generator-Modified-Codes.zipProject Video
Filed Under: Electronic Projects
Filed Under: Electronic Projects
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