What is encryption?

Encryption is the process of transforming plaintext data into an unreadable format (ciphertext) using an algorithm and a key, so that only authorized parties with the correct decryption key can read it. Symmetric encryption: same key for encryption and decryption (AES, 3DES) — fast, used for bulk data. Asymmetric encryption: uses a public key (encrypt) and private key (decrypt) pair (RSA, ECC) — slower, used for key exchange and digital signatures. At rest: encrypting stored data (database encryption, full-disk encryption). In transit: encrypting data over the network (TLS/HTTPS, SSH, VPN). End-to-end: data encrypted by the sender and only decryptable by the recipient (Signal protocol, WhatsApp). Encryption is a cornerstone of confidentiality in the CIA triad.