Cryptography is the practice and study of techniques for secure communication and data storage in the presence of third parties, often referred to as adversaries. Rooted in mathematical theory and computer science, cryptography enables the encryption and decryption of information, effectively transforming readable data into unintelligible code and vice versa. Originally used for military and espionage purposes, cryptography has evolved to become an essential component of modern cybersecurity, safeguarding everything from online transactions and confidential communications to digital identities. It forms the backbone of various technologies, including secure email services, e-commerce platforms, and cryptocurrencies like Bitcoin. By applying algorithms and cryptographic keys, it ensures the confidentiality, integrity, and authenticity of data, allowing for secure transmission and storage in an increasingly interconnected digital world.