Also known as: Transport Layer Security · SSL · HTTPS
TLS (Transport Layer Security) is the cryptographic protocol that encrypts data in transit between clients and servers, providing confidentiality, integrity, and server authentication — most visibly as the S in HTTPS.
TLS superseded SSL, though the older name persists colloquially and in library names. TLS 1.3 substantially simplified the protocol, removing legacy cipher suites that had been the source of numerous downgrade and padding-oracle attacks, and reduced handshake latency.
TLS protects data in transit only. It says nothing about whether the server stores data securely, whether the endpoint is trustworthy, or whether the content is legitimate — a padlock icon confirms an encrypted channel, not a safe destination.
Certificate Authority
A certificate authority (CA) is a trusted organisation that issues digital certificates binding a cryptographic public key to a verified identity, such as a domain name, enabling encrypted and authenticated connections.
End-to-End Encryption
End-to-end encryption (E2EE) is a system in which messages are encrypted on the sender's device and decrypted only on the recipient's, so that no intermediary — including the service provider — can read the content in transit or at rest on its servers.
Encryption at Rest
Encryption at rest is the encryption of stored data — on disks, in databases, or in backups — so that physical access to the storage medium does not yield readable data.
Metadata
Metadata is the information surrounding a communication rather than its content — who contacted whom, when, for how long, from where, and how frequently — which remains visible even when the content itself is encrypted.