Cipher

Introduction:

In the realm of cryptography, ciphers play a crucial role in ensuring secure communication and data protection. A cipher is an algorithmic technique used to perform encryption and decryption, following a series of well-defined steps. In this article, we will delve into the world of ciphers, understanding their significance and exploring the algorithms used for encryption and decryption.

Understanding Ciphers:

A cipher is essentially a method of transforming plaintext into ciphertext, making it unintelligible to unauthorized users. The encryption process involves applying mathematical operations and substitutions to convert the original message into a secret code. This code can then be decrypted by the intended recipient using the corresponding decryption algorithm.

Types of Ciphers:

Substitution Ciphers:

Substitution ciphers replace each letter of the plaintext with another letter or symbol. One of the most well-known substitution ciphers is the Caesar cipher, which involves shifting each letter by a fixed number of positions in the alphabet.

Transposition Ciphers:

Transposition ciphers rearrange the order of characters or blocks in the plaintext to create the ciphertext. One popular transposition cipher is the Rail Fence cipher, which writes the message in a zigzag pattern and then reads it off row by row.

Links

Code Examples

C#
string EncryptCaesar(string plaintext, int shift)
{
    string ciphertext = "";
    foreach (char c in plaintext)
    {
        if (Char.IsLetter(c))
        {
            char encryptedChar = (char)(((c + shift - 'A') % 26) + 'A');
            ciphertext += encryptedChar;
        }
        else
        {
            ciphertext += c;
        }
    }
    return ciphertext;
}

JavaScript
function encryptCaesar(plaintext, shift) {
    let ciphertext = "";
    for (let i = 0; i < plaintext.length; i++) {
        let charCode = plaintext.charCodeAt(i);
        if (charCode >= 65 && charCode <= 90) {
            let encryptedCharCode = ((charCode - 65 + shift) % 26) + 65;
            ciphertext += String.fromCharCode(encryptedCharCode);
        } else {
            ciphertext += plaintext[i];
        }
    }
    return ciphertext;
}

Python
def encrypt_caesar(plaintext, shift):
    ciphertext = ""
    for c in plaintext:
        if c.isalpha():
            encrypted_char = chr((ord(c.upper()) - 65 + shift) % 26 + 65)
            ciphertext += encrypted_char
        else:
            ciphertext += c
    return ciphertext

PHP
function encryptCaesar($plaintext, $shift) {
    $ciphertext = "";
    for ($i = 0; $i < strlen($plaintext); $i++) {
        $charCode = ord($plaintext[$i]);
        if ($charCode >= 65 && $charCode <= 90) {
            $encryptedCharCode = (($charCode - 65 + $shift) % 26) + 65;
            $ciphertext .= chr($encryptedCharCode);
        } else {
            $ciphertext .= $plaintext[$i];
        }
    }
    return $ciphertext;
}

Conclusion