Learn Caesar & Playfair Ciphers: Essential Cryptography Lessons 🔐

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CNS LESSON-3 SYMMETRIC CIPHER MODEL,CHARACTERISTICS OF CRYPTOGRAPHIC SYSTEMS,CRYPTANALYTIC ATTACKS:
https://youtu.be/iWthhpNa3r4

CNS LESSON -2 SECURITY ATTACKS,SERVICES,MECHANISMS
https://youtu.be/ymJh86z6Ztg

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INTRODUCTION,COMPUTER,NETWORK,INTERNET SECURITY,OSI SECURITY ARCHITECTURE
https://youtu.be/XdZEaWVN_OM


#cryptographyandnetworksecurity
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Classical encryption techniques help us to illustrate the basic approaches for symmetric encryption used today and the types of cryptanalytic attacks that must be anticipated. The two Basic building blocks of all encryption technique are substitution and transposition.
In this video We explore the classical substitution techniques of caesar cipher,mono aplhabetic cipher and playfair cipher.

A substitution technique is one in which the letters of plaintext are replaced by other letters or by numbers or symbols. If the plaintext is viewed as a sequence of bits, then substitution involves replacing plaintext bit patterns with ciphertext bit patterns.

Caesar cipher replaces each letter by a letter standing three places further down the alphabet.

We have Caesar cipher as:
c = E(k, p) = (p + k) mod (26)
p = D(k, c) = (c – k) mod (26)

Mono alphabetic ciphers allows an arbitrary substitution, where the translation alphabet can be any permutation of the 26 alphabetic characters.
Each plaintext letter maps to a different random cipher text letter,hence key is 26 letters long

The best-known multiple-letter encryption cipher is the Playfair, which treats digrams in the plaintext as single units and translates these units into ciphertext digrams


In playfair cipher , Plaintext is encrypted two letters at a time

1.If a pair is a repeated letter, insert filler like 'X’
2.If both letters fall in the same row, replace each with letter to right (wrapping back to start from end)

3.If both letters fall in the same column, replace each with the letter below it (wrapping to top from bottom)

4.Otherwise each letter is replaced by the letter in the same row and in the column of the other letter of the pair
#Playfaircipher

#Caesarcipher
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