This document provides an introduction to cryptography. It defines cryptography as the science of hiding information to provide confidentiality, integrity, authentication, and non-repudiation. The document then summarizes the history of cryptography, the main types of cryptography including encryption, decryption, hashing, and steganography. It also describes symmetric and asymmetric cryptographic algorithms like AES, RSA, and hash functions like MD5 and SHA-1/2. The document concludes by emphasizing the safe use of standard algorithms and protection of private keys.