The science and practice of secure communication in the presence of third parties called adversaries. It involves creating written or generated codes that allow information to be kept secret. Cryptography encompasses various techniques such as encryption (scrambling data so it’s unreadable without a key), decryption (making the scrambled data readable again with the correct key), hash functions (transforming data into fixed-size strings of characters), and digital signatures (verifying the sender’s identity and the integrity of the data). It’s essential for securing transactions, communications, and data in many fields, including finance, telecommunications, and national security.