{"id":101,"date":"2023-06-11T19:39:13","date_gmt":"2023-06-11T19:39:13","guid":{"rendered":"https:\/\/learnlearn.uk\/edexcel-igcse-computer-science\/?page_id=101"},"modified":"2023-06-17T08:39:08","modified_gmt":"2023-06-17T08:39:08","slug":"vigenere-cipher","status":"publish","type":"page","link":"https:\/\/learnlearn.uk\/edexcel-igcse-computer-science\/vigenere-cipher\/","title":{"rendered":"Vigenere Cipher"},"content":{"rendered":"
\n

Vigenere<\/h2>\n
\n\n

Vigen\u00e8re Cipher<\/h3>\n

\"Woodcut<\/a><\/p>\n

\n
\n
\n
\n
\n
\n
\n
\n
\n
\n

The Vigen\u00e8re cipher is a polyalphabetic substitution cipher that was developed in the 16th century by a French cryptographer named Blaise de Vigen\u00e8re. It is named after him due to his contribution to the development and popularization of the cipher.<\/p>\n

Blaise de Vigen\u00e8re enhanced the earlier Alberti cipher, invented by Leon Battista Alberti in the 15th century. The Alberti cipher used a single mixed alphabet and a “Cipher Disk” device for encryption and decryption. Vigen\u00e8re’s improvement introduced the use of a repeating keyword or phrase to determine shifts, making it a more secure polyalphabetic cipher compared to monoalphabetic ciphers like the Caesar cipher.<\/p>\n

The Vigen\u00e8re cipher was widely acclaimed and considered unbreakable for many years, earning the name “le chiffre ind\u00e9chiffrable” or “the indecipherable cipher” in French. However, in the mid-19th century, mathematician Charles Babbage discovered a method to crack it using frequency analysis<\/strong>.<\/p>\n

Despite its vulnerability, the Vigen\u00e8re cipher had a significant impact on cryptography. It paved the way for the development of more advanced ciphers and encryption techniques. Today, it is commonly used as an educational tool to introduce polyalphabetic substitution ciphers and emphasize the importance of key management in cryptography.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

\n
\n
\n
\n
It has featured numerous times on a number of different movies<\/a>!<\/div>\n<\/div>\n<\/div>\n<\/form>\n<\/div>\n\n<\/div>

Encryption Process<\/h2>\n
\n\n

Encrypting a Message<\/h3>\n

\"vigenere-square\"<\/a><\/p>\n

    \n
  1. Choose a secret keyword or phrase (e.g., “SECRET”).<\/li>\n
  2. Write down the message you want to encrypt (e.g., “HELLO WORLD”).<\/li>\n
  3. Convert the keyword and message to uppercase and remove any spaces or special characters.<\/li>\n
  4. Using the Vigenere table(one the right) Find the row corresponding to the first letter of the keyword and the column corresponding to the first letter of the message. The intersection of the row and column represents the encrypted letter.\n