What Is Encryption? How Data Is Protected
Encryption is the process of transforming readable data (plaintext) into an unreadable format (ciphertext) using a mathematical algorithm and a key. Only parties holding the correct key can decrypt the ciphertext back to plaintext. Encryption is the foundation of secure communication, stored data protection, and digital identity.
Symmetric vs Asymmetric Encryption
Symmetric encryption (AES, ChaCha20) uses the same key to encrypt and decrypt. It is fast and suitable for bulk data. Asymmetric encryption (RSA, ECC) uses a key pair: a public key encrypts, a private key decrypts. It is slower but solves key distribution. In practice, TLS uses asymmetric encryption to exchange a symmetric session key, then bulk-encrypts data symmetrically.
How TLS/HTTPS Works
When your browser connects to https://example.com, TLS negotiates a cipher suite, the server presents its certificate (signed by a trusted CA), and both sides use Diffie-Hellman key exchange to agree on a shared session key without transmitting it. All subsequent traffic is encrypted with AES-256-GCM or ChaCha20-Poly1305.
Encryption at Rest vs in Transit
Encryption in transit (TLS) protects data moving across a network. Encryption at rest protects data stored on disk — databases, backups, cloud storage. Both are needed: a breach of stored data is just as damaging as intercepted traffic. Full-disk encryption (FileVault, BitLocker, LUKS) and transparent database encryption address the at-rest layer.