Secret writing, also known as cryptography, is the practice of encoding messages to keep their content hidden from unauthorized readers. This technique has been used throughout history for various purposes, including military communication and personal privacy. By transforming readable text into a coded format, secret writing ensures that only those with the correct key or knowledge can decipher the message. There are many methods of secret writing, such as ciphers and steganography. Ciphers replace letters or words with other symbols or letters, while steganography hides messages within other non-secret texts or images. Both techniques have evolved with technology, leading to modern applications in digital security and data protection.