![]() Write the keyword repeatedly until it matches the length of the plaintext message: STACKZEROSTACKZ.To encrypt the plaintext message “MALWAREANALYSIS” using the Vigenere Cipher with the keyword “STACKZERO”, we must follow the following steps: Here’s an example of the Vigenere Cipher in action: Each letter in the keyword is then used to shift the corresponding letter in the plaintext message. ![]() The keyword is repeated as many times as necessary to match the length of the plaintext message. The Vigenere Cipher works by using a series of interwoven Caesar ciphers based on a keyword. Giovan Battista Bellaso invented it in the 16th century and Blaise de Vigenere popularized it in the 19th century. The Vigenere Cipher is a polyalphabetic substitution cipher, which means that it uses multiple substitution alphabets instead of just one. It also serves as a basic building block for more complex substitution ciphers, which use multiple shifts or other substitution methods to make the cipher more secure. Frequency analysis, which involves analyzing the frequency of each letter in the ciphertext to determine the most likely shift value, can easily break it.ĭespite its weaknesses, the Caesar Cipher has been used throughout history for simple encryption tasks, as it is easy to understand and implement. The Caesar Cipher is a very weak cipher, as there are only 25 possible keys (since a shift of 26 would simply result in the original plaintext). In this case, the receiver would shift the letters back by 4 positions to get the original plaintext: STACKZERO. To decrypt the ciphertext, the receiver simply shifts the letters back to the same number of positions. Here’s an example of the Caesar Cipher in action: This is the table that we can derive from the key 4: The key for the Caesar Cipher is the number of positions to shift the letters. ![]() The Caesar Cipher works by shifting each letter of the plaintext a fixed number of positions down the alphabet.įor example, if the shift is 4 the letter “A” becomes “E”, “B” becomes “F”, and so on. It was named after Julius Caesar, who allegedly used it to communicate with his generals. The Caesar Cipher, also known as the shift cipher, is one of the simplest substitution ciphers. For example, replaces “A” with “Z”, “B” with “Y”, and so on. The Atbash cipher is a simple substitution cipher that replaces each letter with its corresponding letter at the opposite end of the alphabet. One of the earliest known examples of a substitution cipher is the Atbash cipher, which Hebrews used to encode their alphabet. The origins of substitution ciphers can be traced back to ancient civilizations. Here is an overview of their history: The Origins of Substitution Ciphers Several populations have used substitution ciphers to protect sensitive information.
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