Cryptography

PRESENTED TO Prof. Nesreen I. Ziedan

PRESENTED BY

Ashraf Saeed Teleb Aly Mahmoud Samy Radwan

Muhamad Gameel Sara Abd Elhamid

Implementing Vigenere cipher using logic gates contents :1-Aknowlegment2-Introduction to cryptography 3-Historical timeline 4-Veginere cipher5-Project parts 5.1-Input 5.2-Adder 5.3-Mermory 5.4-Correction Circuit 5.5-Display 5.6-Power 6-Notes on ic’s 7-References and resources

1-aknowlegment

Prof. Nesreen I. ZiedanComputer and Systems Engineering DepartmentZagazig UniversityFor giving us the chance to live this wonderful experience

Prof.Dan Boneh computer science stanford university For providing us with the theoretical basis through his great mooc on corsera platform .

2-Cryptography Cryptography is the science of encoding messages or information in such a way that only authorized parties can read it.In an encryption scheme, the message or information, referred to as plaintext, is encrypted using an encryption algorithm, generating ciphertext that can only be read if decrypted.Decryption is the reverse process to Encryption. Decryption creates a Plaintext from a Ciphertext only and only if the keys is known .

Cryptography has a wide range of applications : Electronic Money , Secure Network Communications , Electronic Signatures and of caurse military applications .Spies, soldiers, hackers, pirates, royalty, merchants, tyrants, political activists, Internet shoppers, and anyone who has ever needed to share secrets with trusted friends have relied on cryptography to make sure their secrets stay secret.

3-History of cryptography:it’s clear that the need of secret way of writting was demanding since early ages such that most of the ancient civilizations had there own cryptography machines .

ancient roma : Julius Caesar used what is know after him - Caesar cipher- in which each letter in the plaintext was replaced by a letter some fixed number of positions further down the alphabet. Suetonius reports that Julius Caesar used it with a shift of three to communicate with his generals. The Greeks of Classical times are said to have known of ciphers (e.g., the scytale transposition cipher claimed to have been used by the Spartan military).

transposition ciphers, which rearrange the order of letters in a message (e.g., 'hello world' becomes 'ehlol owrdl' in a trivially simple rearrangement scheme).Reconstructed ancient Greek scytaleAncient Egypt Atbash is an example of an early Hebrew cipher. The earliest known use of cryptography is some carved ciphertext on stone in Egypt (ca 1900 BCE).In India, the 2000-year old Kamasutra of Vātsyāyana speaks of two different kinds of ciphers called Kautiliyam and Mulavediya. In the Kautiliyam, the cipher letter substitutions are based on phonetic relations, such as vowels becoming consonants. In the Mulavediya, the cipher alphabet consists of pairing letters and using the reciprocal ones.

4-veginere cipher

It was possibly first described in 1553 by Italian cryptographer Giovan Battista Bellaso (though it has been reinvented many times, including by Blaise de Vigenère). It is thought to have remained unbroken until Charles Babbage, considered to be the father of computers, broke it in the 19th century. Blaise de Vigenère The Vigenère cipher consists of several Caesar ciphers in sequence with different shift values.

Algebraic description:

5-PROJECT LAYOUT •letters are represented in integer numbers , from 1 to 26 •character's are received as ascii codes from ps/2 keyboard and then modulated using Arduino into corresponding integers•key character's are saved in the memory while text head to the adder where it’s simply added to the key •the modulo function as achieved using the correction circuit •integers are transformed back into ascii and finally displayed on LCD

5.1-InputThe project uses ps2 keyboard

physically , ps2 connector consisits of 6 pins as shown below .

data (ASCII code ) are transmitted serially over one line synchronous with a clock which make a challenge to transform it into parallel form .

This problem was solved using Arduino giving an output of five data lines for five data bits representing all the 26 English character's .Arduino code :#include <LiquidCrystal.h>#include <PS2Keyboard.h>//LiquidCrystal lcd(A0 , A1, A2, A3,A4, A5);const int DataPin = 8;const int IRQpin = 3;PS2Keyboard keyboard;void setup() {pinMode(7, OUTPUT);pinMode(9, OUTPUT); pinMode(10, OUTPUT); pinMode(11, OUTPUT); pinMode(12, OUTPUT); pinMode(13, OUTPUT); pinMode(A0, INPUT); pinMode(A1, INPUT); pinMode(A2, INPUT); pinMode(A3, INPUT); pinMode(A4, INPUT);

pinMode(A5, INPUT); pinMode(6, OUTPUT); keyboard.begin(DataPin, IRQpin, PS2Keymap_US); Serial.begin(9600); Serial.println("Enter your text: "); // lcd.println("Enter your text: "); }void loop() { int y; digitalWrite(6,LOW) ; if (keyboard.available()) { char c = keyboard.read(); int x=int(c)-96; Serial.print(c); Serial.print(" "); Serial.println( x); // lcd.print(c); // lcd.display(); // convert character from keyboard to binary start from 0 to 25

if(x==-64){ x=0;} if(x==31){x=27; // lcd.clear(); } if((x>-1 && x<28) ){ digitalWrite(6,HIGH); for(int i=0;i<5;i++){ if(x%2==0){ digitalWrite(9+i, LOW); }else if(x%2==1){ digitalWrite(9+i, HIGH); } x=x/2; }}}}

5.2-Adder A Long - term outlook would show an overflow problem that takes another bit being added to the five data bit .overcoming this problem . two-four- bit full adder can simply add the text and key characters generating the cipher text or subtracting them and retrieving plain text again . the full adder ic is 74HC283 which is a 4 bit full adder with fast carry six xor gates are used to add the functionality of suntraction( Decrption ).the xor ic is 74LS86 both of the xor and the full adder make ripple adder capable of encrypting and decrypting massages .

5.3-MermoryA small (8*5 bit ) memory is built using 5 ic each contains 8 latches .Used to save the key such that each character is saved in parallel in the five ic’s .the latches ic can work on four modes controlled by 2 enable lines

the latches shows the stored bit all the time so in order to read one character , 5 multiplexer are used.A counter is used to address the memory , such that it’s activated with each key stroke .it also plays a vital role when entering the plain text.

5.4-Correction Circuit (round robin )Consists of detection and a ripple adder The detection circuit detects error resulting from the absence of the modulo function and reports with a single bit flag .

The ripple adder adds or subtract 26 depending on the operation, encryption or decryption ****************************normally ... the input of the xor gates is -26 and one flag (ENC/DEC) . in case ENC , the flage is zero so the input to the adder is 26.in case of DEC , the flag is 1 so the input to the adder is 26.

5.5-Display Again with the five data bit representing integers from 1 to 26.. the arduino transforms this output into ASCII code which is displayed on the LCD.The Arduino has an enable to read every key stroke .

5.6-Power

The project uses 17805 which has a fixed output of 5 volt and mac current of 1.5 amperes.This ic is going to power the ic’s of the circuit and it’s fed from a 9 volt battery.

The arduino is directly connected to a 9-volt battery.

6-Notes on ic’s :The projects uses 74HC family which is CMOS technology,, it has a propagation delay of 9 ns and toggle speed of 50MHz .The typical supply voltage is 5 volt anf the consumption of the gate per 1MHz is 0.5mW .

7-Refrences and Resouces 1- Cryptography…. mooc …. stanford university https://www.coursera.org/course/crypto 2-Cryptography…. mooc …. University of Maryland https://www.coursera.org/course/cryptography 3-Hacking Secret Ciphers with Python: A beginner's guide to cryptography and computer programming with Python