コード (Cipher) is a method used to transform information into a format that is unreadable to anyone who does not have the key to decode it. This technique is essential for ensuring the confidentiality of sensitive data, such as personal information or classified documents. Ciphers can be simple, like the Caesar cipher, which shifts letters in the alphabet, or more complex, like AES (Advanced Encryption Standard), which uses intricate algorithms. Ciphers have been used throughout history, from ancient times to modern digital communication. They play a crucial role in cybersecurity, protecting data transmitted over the internet. Understanding ciphers is important for anyone interested in fields like cryptography or information security, as they help safeguard privacy and secure communications.