What is cryptography？

Cryptography is the practice of securing communication by converting plain text into an unreadable format, known as ciphertext, using various algorithms and mathematical calculations. Cryptography involves creating codes or ciphers that can only be understood by someone who has the knowledge required to decode them.

Cryptography has been used for centuries to protect secrets and sensitive information. In modern times, cryptography plays a critical role in securing electronic communication and digital data. It is commonly used to protect information such as passwords, credit card numbers, and other important data.

There are two main types of cryptography: symmetric key cryptography and asymmetric key cryptography. Symmetric cryptography uses the same key to encrypt and decrypt data, while asymmetric cryptography uses different keys for encryption and decryption.

Cryptography is used in various applications, ranging from secure communication protocols like SSL and TLS to cryptocurrencies like Bitcoin and Ethereum. It is also used in many other fields, including military and intelligence operations, banking and finance, and e-commerce.

Overall, cryptography is a vital component of modern information security systems, providing a way to secure communication and data against unauthorized access, interception, and exploitation.