2012

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    Digital data scrambler using pic 18f452 microcontroller
    (UMT.Lahore, 2012) Akbare Yaqub
    With the invention of electronic ICs came the ease and simplicity with which we can design and test numerous ideas. The last few decades of the 20th century have seen many advances in the field of cryptography to improve the security of the transmitted data efficiently. Numerous ideas and algorithms have been devised and tested for the security of data transmission but the scheme presented in this thesis is very simple and easy to implement in hardware and yet it is very secure and reliable.A digital speech/data scrambler using PIC 18F452 Microcontroller is studied, designed and developed. The main theme of my Thesis “Digital Speech/Data Scrambling” is that a piece of data information is scrambled using pseudo random numbers and is transmitted. On the receiving end it can be descrambled with the help of the same pseudo random numbers which are generated at the receiving end in synchronism with the transmitted numbers to extract the original data. Although on the face of it, it seems very simple but in real world synchronization of the transmitter and the receiver and synchronously producing the same sequence of numbers at the both ends requires some special effort which is explained in this thesis in due course of time.Mathematically:If “DS” is the original digital data, and NT is the pseudo random number, then the scrambled output data So will be:So = Ds NT The transmitted scrambled data which is also received at the input of the receiver.Ds NT NR = DS The original unscrambled data because NT = NR.The unscrambling process seems very simple and it is indeed so but its practical implementation requires some special efforts which will become obvious as the progress is made in this thesis.The heart and soul of this thesis is the generation of NT, which is the pseudo random numbers at the transmitting and the receiving ends and synchronization between these numbers. Out of numerous methods available for the generation of NT, a simple and easy-to-implement technique in hardware has been developed and adopted in this thesis so as to enable implementation of the hardware feasible. This technique is explained in detail in the Chapters to follow of the thesis. Chapter 3 deals with the hardware details of the microcontroller and Chapter 3 explains software requirements of the microcontroller. Chapter 4 deals with the interrupt system of the microcontroller and the basic principles of serial communication are outlines in Chapter5. The complete program (code) is given in Chapter 6 with requisite explanation. The conclusions are drawn in Chapter 7.