Transport Layer Security (TLS) is a cryptographic protocol that ensures privacy and data integrity for communications over computer networks, most notably the Internet. It is the successor to the now-deprecated Secure Sockets Layer (SSL) protocol, and today it is the standard for securing web traffic and many other types of network communications.
Key Functions of TLS
TLS provides three essential security properties:
• Encryption: TLS encrypts data transmitted between two endpoints (such as a web browser and a server), making it unreadable to unauthorized parties and protecting it from eavesdropping.
• Authentication: TLS verifies the identities of the parties involved in the communication, ensuring that users are connected to the legitimate server and not an imposter.
• Integrity: TLS ensures that the data sent and received has not been tampered with or altered during transit.
How TLS Works
TLS operates primarily at the transport layer of the OSI model, but it is used to secure application-layer protocols like HTTP (for web browsing, resulting in HTTPS), SMTP (for email), and others. The process of establishing a secure TLS connection typically involves:
1. TLS Handshake: When a client (like a web browser) connects to a server, a handshake process begins.During this handshake:
• The client and server agree on which cryptographic algorithms (cipher suites) to use.
• The server presents its digital certificate, issued by a trusted Certificate Authority (CA), to prove its identity.
• The client verifies the certificate and, if valid, both parties securely exchange keys to establish an encrypted session.
2. Data Encryption: Once the handshake is complete, all data transmitted between the client and server is encrypted using the agreed-upon keys and algorithms.
3. Session Integrity: TLS uses cryptographic checks to ensure that data has not been altered or tampered with during transmission.
TLS Certificates
A TLS certificate (often still called an “SSL certificate” due to historical reasons) is a digital document used to authenticate the server and facilitate the encrypted connection. It contains information about the domain, the server’s public key, and the CA’s digital signature.
TLS vs. SSL
While the terms TLS and SSL are sometimes used interchangeably, all versions of SSL are now considered insecure and deprecated. TLS is more secure and is the protocol currently used for encrypted communications on the Internet