imbricate cryptology

UDML COLLEGE OF ENGINEERING A SEMINAR PRESENTATION ON: 

Presented by: VED PRAKASH SAINI 9/19/2011 3:02 AM UDML COLLEGE OF ENGINEERING A SEMINAR PRESENTATION ON Imbricate Cryptology 1

What is Cryptology ???: 

What is Cryptology ??? 9/19/2011 3:02 AM Cryptology is the secure communication, formed from the Greek words kryptós , "hidden", and lógos , "word". 2

What is cryptology?: 

What is cryptology? 9/19/2011 3:02 AM CRYPTOLOGY CRYPTOGRAPHY CRYPTANALYSIS 3

Cryptanalysis: 

Cryptanalysis 9/19/2011 3:02 AM 4

Cryptology Terms…………..………: 

Cryptology Terms…………..……… 9/19/2011 3:02 AM Plaintext A message in ordinary language Codetext or ciphertext The plain text message transformed using a code or cipher so that it cannot be read without knowing the code or cipher 5

Cryptology Terms……………..………..: 

Cryptology Terms……………..……….. 9/19/2011 3:02 AM Cryptography The study of how to conceal the meaning of messages (encryption) using codes and ciphers. Sometimes more generally used as a synonym for Cryptology Cryptanalysis The study of how to discover the meaning of hidden messages (decryption) 6

Cryptology Terms………….……………: 

Cryptology Terms………….…………… 9/19/2011 3:02 AM Code A system for altering a text by substituting different words or symbols for words or phrases in the plaintext Cipher We can refer encryption & decryption as a chiper . A cipher can serve millions of communication pairs. 7

Cryptography components: 

Cryptography components 9/19/2011 3:02 AM 8

Encryption and decryption: 

Encryption and decryption 9/19/2011 3:02 AM 9

Slide 10: 

In cryptography, the encryption/decryption algorithms are public; the keys are secret. Note: 9/19/2011 3:02 AM 10

Types of Cryptology: 

Types of Cryptology 9/19/2011 3:02 AM Symmetric cryptology (secret key) Asymmetric cryptology (public key) 11

Symmetric Encryption: 

Symmetric Encryption 9/19/2011 3:02 AM If the sender and recipient must have the same key in order to encode or decode the protected information , then the cipher is a symmetric key cipher since everyone uses the same key for the same message . The main problem is that the secret key must somehow be given to both the sender and recipient privately. For this reason, symmetric key (or secret key ) ciphers. 12

Symmetric-key cryptography: 

Symmetric-key cryptography 9/19/2011 3:02 AM 13

Slide 14: 

In symmetric-key cryptography, the same key is used by the sender (for encryption) and the receiver (for decryption). The key is shared. Note: 9/19/2011 3:02 AM 14

Slide 15: 

In symmetric-key cryptography, the same key is used in both directions. Note: 9/19/2011 3:02 AM 15

Slide 16: 

9/19/2011 3:02 AM 16 Traditional cipher Substitution cipher Transposition cipher monoalphabetic polyalphabetic

Substitution Cipher: 

Substitution Cipher 9/19/2011 3:02 AM Permute A-Z randomly: A B C D E F G H I J K L M N O P… becomes H Q A W I N F T E B X S F O P C… Substitute H for A, Q for B, etc. Example Plaintext: OLINCOLLEGE Key: PSEOAPSSIFI 17

Monoalphabetic Cipher: 

Monoalphabetic Cipher 9/19/2011 3:02 AM rather than just shifting the alphabet could shuffle (jumble) the letters arbitrarily each plaintext letter maps to a different random ciphertext letter hence key is 26 letters long Plain: abcdefghijklmnopqrstuvwxyz Cipher: DKVQFIBJWPESCXHTMYAUOLRGZN Plaintext: ifwewishtoreplaceletters Ciphertext: WIRFRWAJUHYFTSDVFSFUUFYA 18

Polyalphabetic Ciphers: 

Polyalphabetic Ciphers 9/19/2011 3:02 AM polyalphabetic substitution ciphers improve security using multiple cipher alphabets use a key to select which alphabet is used for each letter of the message repeat from start after end of key is reached 19

Slide 20: 

In monoalphabetic substitution, the relationship between a character in the plaintext to the character in the ciphertext is always one-to-one. Note: 9/19/2011 3:02 AM 20

Slide 21: 

In polyalphabetic substitution, the relationship between a character in the plaintext and a character in the ciphertext is one-to-many. Note: 9/19/2011 3:02 AM 21

Example of monoalphabetic substitution: 

Example of monoalphabetic substitution 9/19/2011 3:02 AM 22

Caesar cipher: 

Caesar cipher 9/19/2011 3:02 AM 23

Caesar Cipher: 

Caesar Cipher 9/19/2011 3:02 AM earliest known substitution cipher by Julius Caesar first attested use in military affairs replaces each letter by 3rd letter on example: meet me after the party PHHW PH DIWHU WKH SDUWB 24

Caesar Cipher: 

Caesar Cipher 9/19/2011 3:02 AM can define transformation as: a b c d e f g h i j k l m n o p q r s t u v w x y z D E F G H I J K L M N O P Q R S T U V W X Y Z A B C mathematically give each letter a number a b c d e f g h i j k l m n o p q r s t u v w x y z 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 25

Transposition Ciphers: 

Transposition Ciphers 9/19/2011 3:02 AM now consider classical transposition or permutation ciphers these hide the message by rearranging the letter order 26

Row Transposition Ciphers: 

Row Transposition Ciphers 9/19/2011 3:02 AM is a more complex transposition write letters of message out in rows over a specified number of columns then reorder the columns according to some key before reading off the rows Key: 4312567 Column Out 3 4 2 1 5 6 7 Plaintext: a t t a c k p o s t p o n e d u n t i l t w o a m x y z Ciphertext: TTNAAPTMTSUOAODWCOIXKNLYPETZ 27

Slide 28: 

Your questions are welcome! 9/19/2011 3:02 AM 28