# Polyalphabetic cipher encryption and decryption program in c. C++ Program to Implement the Vigenere Cypher 2022-10-13

Polyalphabetic cipher encryption and decryption program in c Rating: 7,5/10 173 reviews

A polyalphabetic cipher is a type of encryption algorithm that uses multiple substitution alphabets to obscure the meaning of a message. The basic idea behind a polyalphabetic cipher is to use multiple substitution alphabets, rather than just one, to obscure the message. This makes it more difficult for attackers to break the cipher, as they must determine which alphabet was used for each letter of the message.

One popular example of a polyalphabetic cipher is the Vigenère cipher, which was invented in the 16th century and is still in use today. The Vigenère cipher uses a series of interwoven Caesar ciphers, each with a different shift value, to encrypt the message. The shift value for each Caesar cipher is determined by a key word, which is used to generate a repeating sequence of shift values.

To implement a polyalphabetic cipher in C, we will first need to define a function for encrypting a message using a given key. This function will take two arguments: the message to be encrypted, and the key. It will return the encrypted message.

The first step in the encryption process is to convert the message and the key into arrays of integers, with each integer representing the position of a letter in the alphabet. For example, the letter 'A' would be represented as 0, 'B' as 1, and so on.

Next, we will iterate through the message array and use the corresponding value in the key array to determine the shift value for the current letter. We will then apply the Caesar cipher to encrypt the current letter using this shift value.

Finally, we will return the encrypted message as a string.

To decrypt a message encrypted with this cipher, we will simply need to define a function that performs the inverse operation. This function will take the same arguments as the encryption function, but will return the decrypted message rather than the encrypted message.

To decrypt the message, we will again convert the message and the key into arrays of integers, and then iterate through the message array. For each letter in the message, we will use the corresponding value in the key array to determine the shift value, and then apply the inverse of the Caesar cipher to decrypt the letter.

By following these steps, we can create a simple polyalphabetic cipher program in C that can encrypt and decrypt messages using a variety of substitution alphabets. While this type of cipher can be effective at obscuring the meaning of a message, it is still vulnerable to certain types of attacks, such as frequency analysis, and should be used in conjunction with other security measures to provide robust protection for sensitive information.

## Rail Fence Cipher

On the other hand, Private key is only used to decrypt the encrypted message. What is Caesar Cipher? Vigenere Cipher is somewhat polyalphabetic substitution strategy. The relative frequencies of individual letters show a much larger variety than that of diagrams. This is a C Program to implement Monoalphabetic Cipher. At long last the encoded message content is: Encoded Message: ALPNFHDJAFVKCLATIC The calculation can be communicated in arithmetical structure as given underneath.

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## Hill Cipher in C and C++ (Encryption and Decryption)

New Generated Key: HELLOHELLOHELLOHEL For encryption take first letter of message and new key i. The Vigenère cipher has several Caesar ciphers in sequence with different shift values. Therefore, row Land column Aof the Vigenère square are used, namely L. It employs a form of Algorithm It is similar to Awould become D, Bwould become E, Ywould become Band so on. Hill in 1929 and in this manner got its name. One command line parameter is required of the form -dkey or -ekey where -e specifies encryption mode and -d specifies decryption mode. For encryption take first letter of message and key i.

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## Caesar Cipher in C and C++ [Encryption & Decryption]

I hope this makes it clear PS: the whole point of doing this was to keep things simple the other way it could have been written: ch-26… i think correct me if I am wrong people…. Encryption INPUT: line 1: message s line 2: key key OUTPUT: line 1: Encrypted message encrypt The following is the Caesar Cipher encryption algorithm program in C++. Repeat this process for all the alphabets in encrypted message. What is Hill Cipher? And if you found this post helpful, then please help us by sharing this post with your friends. Next, in row E from L EMON , the ciphertext Xis located in column T.

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## Vigenere Cipher in C and C++

Army along with other allied forces during World War II. Finally modulo 26 is taken for each element of matrix obtained by multiplication. Original Message: THECRAZYPROGRAMMER Above process can be represented in algebraic form by following equation. It had been utilized as the standard area system from the British Army in World War I and enjoyed considerable from the U. What is Playfair Cipher? There are exceptions and some cipher systems may use slightly more, or fewer, characters when output versus the number that was input. It derives its name from the way in which it is encoded. It is utilized for encryption of alphabetic content.

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## Vigenere Cipher in C and C++

Rehash a similar procedure for every single outstanding letter set in the message content. In cipher or cypher is an encipherment. You are plain IDIOTS. Plaintext letters which fall in the Exact Same column each exchanged by the letter below, with the upper element of this row circularly after the past. The Cipher Algorithm Uses 5×5 Matrix.

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## C code to Encrypt & Decrypt Message using Vernam Cipher

Take the letters in order in Vigenere Cipher Table where T line and H section harmonizes for example A. At different points in the encryption process, the cipher uses a different alphabet from one of the rows. To encrypt, a table of alphabets can be used, termed Vigenère squareor Vigenère table. It involves the use of public and private key, where the public key is known to all and used for encryption. Break down Vigenere Cipher Table, search for letters in order An in segment H, the comparing line will be the primary letters in order of unique message for example T.

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## Polyalphabetic

Here you get encryption and decryption program for hill cipher in C and C++. Take the alphabet in Vigenere Cipher Table where T row and W column coincides i. Thus Tis the second plaintext letter. Plaintext letters which drop in the Exact Same row of this matrix are all replaced from the letter into the right, together with the first component of this row circularly after the past. What is Hill Cipher? Encryption Key: WELCOME Message: Thisistutorialspoint Here we have to obtain a key by repeating the given key till its length becomes equal to original message length. Decryption Key: WELCOME Encrypted Message: PLTUWEXQXZTWMPOTZKBF Take generated key and first alphabet of encrypted message i. Analyze Vigenere Cipher Table, look for alphabet A in column H, the corresponding row will be the first alphabet of original message i.

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## C Program To Encrypt And Decrypt The String (Source Code)

RSA algorithm is bit complex than Ceaser Cypher. It has the alphabet written out 26 times in different rows, each alphabet shifted cyclically to the left compared to the previous alphabet, corresponding to the 26 possible Caesar ciphers. Vigenere Cipher Decryption Encoded Message: ALPNFHDJAFVKCLATIC Key: HELLO New Generated Key: HELLOHELLOHELLOHEL Take first letters in order of scrambled message and produced a key, for example, An and H. To learn more about hill cipher you can visit following link. Decryption: The encrypted message matrix is multiplied by the inverse of key matrix and finally its modulo 26 is taken to get the original message. Which is occupied by another plaintext letter.

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## Hill Cipher in C and C++ (Encryption and Decryption)

Analyze Vigenere Cipher Table, look for alphabet P in column W, the corresponding row will be the first alphabet of original message i. Thus the alphabets of the message are written in a zig-zag manner. After filling it, we traverse the matrix in zig-zag manner to obtain the original text. The cipher content can be created by underneath condition. Get program for caesar cipher in C and C++ for encryption and decryption.

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