Encrypted Data Transfer

Project: 01- Encrypted Data Transfer

Our project deals with the demonstration of modern days’ technology of transmitting data through high security encryption in commercial and military use. We have used a very simple system of Transmitter and receiver module and chipper software for the project. This project gives an outline to a layman about how the modern systems handles and secures electronic data transfers.

HISTORY, DEVELOPMENT & APPLICATIONS - Cryptography has a long and fascinating history. The most complete non-technical account of the subject is Kahn’s The Codebreakers . This book traces cryptography from its initial and limited use by the Egyptians some 4000 years ago, to the twentieth century where it played a crucial role in the outcome of both world wars. Completed in 1963, Kahn’s book covers those aspects of the history which were most significant (up to that time) to the developmentof the subject. The predominant practitioners of the art were those associated with the military, the diplomatic service and government in general. Cryptography was used as a tool to protect national secrets and strategies. The proliferation of computers and communications systems in the 1960s brought with it a demand from the private sector for means to protect information in digital form and to provide security services. Beginning with the work of Feistel at IBMin the early 1970s and culminating in 1977 with the adoption as a U.S. Federal Information Processing Standard for encrypting unclassified information, DES, the Data Encryption Standard, is the most well-known cryptographic mechanism in history. It remains the standard means for securing electronic commerce for many financial institutions around the world.  In 1978 Rivest, Shamir, and Adleman discovered the first practical public-key encryption and signature scheme, now referred to as RSA. The RSA scheme is based on another hard mathematical problem, the intractability of factoring large integers. This application of a hard mathematical problem to cryptography revitalized efforts to find more efficient methods to factor. The 1980s saw major advances in this area but nonewhich rendered the RSA systeminsecure. Another class of powerful and practical public-key schemes was found by ElGamal in 1985. These are also based on the discrete logarithm problem. One of the most significant contributions provided by public-key cryptography is the digital signature. In 1991 the first international standard for digital signatures (ISO/IEC

9796) was adopted. It is based on the RSA public-key scheme. In 1994 the U.S. Government adopted the Digital Signature Standard, a mechanism based on the ElGamal publickey scheme. The search for new public-key schemes, improvements to existing cryptographicmechanisms, and proofs of security continues at a rapid pace. Various standards and infrastructures involving cryptography are being put in place. Security products are being developed to address the security needs of an information intensive society.
The way information is recorded has not changed dramatically over time. Whereas information was typically stored and transmitted on paper, much of it now resides on magnetic media and is transmitted via telecommunications systems, some wireless. What has changed dramatically is the ability to copy and alter information. One can make thousands of identical copies of a piece of information stored electronically and each is indistinguishable from the original. With information on paper, this is much more difficult. What is needed then for a society where information is mostly stored and transmitted in electronic form is a means to ensure information security which is independent of the physical medium recording or conveying it and such that the objectives of information security rely solely on digital information itself.
Project details This project has two parts; they are the Software part and the Hardware part. While the software part is used for encrypting the message to be sent in the transmitter side and decrypting it in the receiver side of the system, the hardware part is there for transmitting and receiving the message using the Morse code. In today’s world though Morse has almost no significance but the easiest way to transmit data in this simple model can only be done using the code. We have slightly modified it according to our use as we will be having LEDs for the data transmission so the ‘Dot’ in is the blinking of the ‘Red’ LED and the ‘Dash’ is the blinking of the ‘Yellow’ LED. As we can transmit 4 bits of data simultaneously, we can use four LEDs for different purpose.
 
Software-
We have used two softwares for the encoding and decoding purpose which will be used in series with each other. First we will put the message in the first software and then the encoded data will be put into the second software. The result of it will be transmitted and will be decoded similarly using the same software in the receiving side. The softwares with .exe extension is available with this pdf.
       

Hardware-  
Description This radio frequency (RF) transmission system employs Amplitude Shift Keying (ASK) with transmitter/receiver (Tx/Rx) pair operating at 434 MHz. The transmitter module takes serial input and transmits these signals through RF. The transmitted signals are received by the receiver module placed away from the source of transmission.  The system allows one way communication between two nodes, namely, transmission and reception. The RF module has been used in conjunction with a set of four channel encoder/decoder ICs. Here HT12E & HT12D have been used as encoder and decoder respectively. The encoder converts the parallel inputs (from the remote switches) into serial set of signals. These signals are serially transferred through RF to the reception point. The decoder is used after the RF receiver to decode the serial format and retrieve the original signals as outputs. These outputs can be observed on corresponding LEDs.
Encoder IC (HT12E) receives parallel data in the form of address bits and control bits. The control signals from remote switches along with 8 address bits constitute a set of 12 parallel signals. The encoder HT12E encodes these parallel signals into serial bits.

Transmission is enabled by providing ground to pin14 which is active low. The control signals are given at pins 10-13 of HT12E. The serial data is fed to the RF transmitter through pin17 of HT12E.
Transmitter, upon receiving serial data from encoder IC (HT12E), transmits it wirelessly to the RF receiver. The receiver, upon receiving these signals, sends them to the decoder IC (HT12D) through pin2. The serial data is received at the data pin (DIN, pin14) of HT12D. The decoder then retrieves the original parallel format from the received serial data.
 
When no signal is received at data pin of HT12D, it remains in standby mode and consumes very less current (less than 1μA) for a voltage of 5V. When signal is received by receiver, it is given to DIN pin (pin14) of HT12D. On reception of signal, oscillator of HT12D gets activated. IC HT12D then decodes the serial data and checks the address bits three times. If these bits match with the local address pins (pins 1-8) of HT12D, then it puts the data bits on its data pins (pins 10-13) and makes the VT pin high. An LED is connected to VT pin (pin17) of the decoder. This LED works as an indicator to indicate a valid transmission. The corresponding output is thus generated at the data pins of decoder IC. A signal is sent by lowering any or all the pins 10-13 of HT12E and corresponding signal is received at receiver’s end (at HT12D). Address bits are configured by using the by using the first 8 pins of both encoder and decoder ICs. To send a particular signal, address bits must be same at encoder and decoder ICs. By configuring the address bits properly, a single RF transmitter can also be used to control different RF receivers of same frequency.  To summarize, on each transmission, 12 bits of data is transmitted consisting of 8 address bits and 4 data bits. The signal is received at receiver’s end which is then fed into decoder IC. If address bits get matched, decoder converts it into parallel data and the corresponding data bits get lowered which could be then used to drive the LEDs. The outputs from this system can either be used in negative logic or NOT gates (like 74LS04) can be incorporated at data pins.
     

COMPONENTS USED  1. HT12D DECODER  
HT12D IC comes from HolTek Company. HT12D is a decoder integrated circuit that belongs to 212 series of decoders. This series of decoders are mainly used for remote control system applications, like burglar alarm, car door controller, security system etc. It is mainly provided to interface RF and infrared circuits. They are paired with 212 series of encoders. The chosen pair of encoder/decoder should have same number of addresses and data format. In simple terms, HT12D converts the serial input into parallel outputs. It decodes the serial addresses and data received by, say, an RF receiver, into parallel data and sends them to output data pins. The serial input data is compared with the local addresses three times continuously. The input data code is decoded when no error or unmatched codes are found. A valid transmission in indicated by a high signal at VT pin. HT12D is capable of decoding 12 bits, of which 8 are address bits and 4 are data bits. The data on 4 bit latch type output pins remain unchanged until new is received.    

Pin Diagram

   
Pin Description  
 Pin Number        
Function        
Name
1  8 BIT ADDRESS PINS FOR INPUT
A0
2                          A1  3                          A2  4                          A3  5                          A4  6                          A5  7                          A6  8                          A7  9  GROUND (0V)  GROUND  10  4 BIT DATA/ADDRESS PINS FOR OUTPUT  D0  11                          D1  12                          D2  13                          D3  14  SERIAL DATA INPUT  INPUT  15  OSCILLATOR OUTPUT  OSC 2  16  OSCILLATOR INPUT  OSC 1  17  VALID TRANSMISSION, ACTIVE HIGH  VT  18  SUPPLY VOLTAGE; 5V (2.4 – 12V)  Vcc          

2. HT12E ENCODER
HT12E is an encoder integrated circuit of 212 series of encoders. They are paired with 212 series of decoders for use in remote control system applications. It is mainly used in interfacing RF and infrared circuits. The chosen pair of encoder/decoder should have same number of addresses and data format. Simply put, HT12E converts the parallel inputs into serial output. It encodes the 12 bit parallel data into serial for transmission through an RF transmitter. These 12 bits are divided into 8 address bits and 4 data bits. HT12E has a transmission enable pin which is active low. When a trigger signal is received on TE pin, the programmed addresses/data are transmitted together with the header bits via an RF or an infrared transmission medium. HT12E begins a 4-word transmission cycle upon receipt of a transmission enable. This cycle is repeated as long as TE is kept low. As soon as TE returns to high, the encoder output completes its final cycle and then stops.
Pin Diagram

Pin Description  
Pin Number  
Function  
Name
1  8 BIT ADDRESS PINS FOR INPUT
A0
2                          A1  3                          A2 4                          A3  5                          A4  6                          A5  7                          A6  8                          A7  9  GROUND (0V)  GROUND  10  4 BIT DATA/ADDRESS PINS FOR INPUT  D0  11                          D1  12                          D2  13                          D3  14  TRANSMISSION ENABLE (ACTIVE LOW)  TE  15  OSCILLATOR OUTPUT  OSC 2  16  OSCILLATOR INPUT  OSC 1  17  VALID TRANSMISSION, ACTIVE HIGH  VT  18  SUPPLY VOLTAGE; 5V (2.4 – 12V)  Vcc      
 
3. RF MODULES (434MHz)
The RF module, as the name suggests, operates at Radio Frequency. The corresponding frequency range varies between 30 kHz & 300 GHz. In this RF system, the digital data is represented as variations in the amplitude of carrier wave. This kind of modulation is known as Amplitude Shift Keying (ASK). Transmission through RF is better than IR (infrared) because of many reasons. Firstly, signals through RF can travel through larger distances making it suitable for long range applications. Also, while IR mostly operates in line-of-sight mode, RF signals can travel even when there is an obstruction between transmitter & receiver. Next, RF transmission is more strong and reliable than IR transmission. RF communication uses a specific frequency unlike IR signals which are affected by other IR emitting sources. This RF module comprises of an RF Transmitter and an RF Receiver. The transmitter/receiver (Tx/Rx) pair operates at a frequency of 434 MHz. An RF transmitter receives serial data and transmits it wirelessly through RF through its antenna connected at pin4. The transmission occurs at the rate of 1Kbps - 10Kbps.The transmitted data is received by an RF receiver operating at the same frequency as that of the transmitter.

The RF module is often used along with a pair of encoder/decoder. The encoder is used for encoding parallel data for transmission feed while reception is decoded by a decoder. HT12E-HT12D, HT640-HT648, etc. are some commonly used encoder/decoder pair ICs.
Pin Diagram  Receiver Module
Transmitter Module

Transmitter Module  
Pin Number    
Function    
Name  1  Ground (0V)  GND  2  Serial Data Input Pin  DATA  3  Supply Voltage (5V)  VCC  4  Antenna Output Pin  ANT

Receiver Module  
Pin Number  
Function  
Name 1  Ground (0V)  GND  2  Serial Data Output Pin  DATA  3  Linear Output Pin; Not Connected  NC  4  Supply Voltage (5V)  VCC  5  Supply Voltage (5V)  VCC  6  Ground (0V)  GND  7  Ground (0V)  GND  8  Antenna Input Pin  ANT
Stills-
 
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