What is TLS?
Transport Layer Security is a cryptographic protocol designed to provide secure communication over a computer network. TLS encrypts the connection between your browser and web servers, ensuring privacy and data integrity. It's the technology behind HTTPS.
Also known as: Transport Layer Security, SSL, SSL/TLS
TLS (Transport Layer Security) is the encryption protocol that secures your web browsing, email, and many other internet communications. When you see HTTPS, TLS is doing the heavy lifting.
TLS vs SSL
- SSL (Secure Sockets Layer): Original protocol, now deprecated
- TLS: Successor to SSL, current standard
- In practice: "SSL" often used to mean TLS
- Use TLS 1.2 or 1.3: Older versions have vulnerabilities
What TLS Provides
Encryption
- Data encrypted in transit
- Unreadable to eavesdroppers
- Protects passwords, messages, financial data
Authentication
- Server proves its identity via certificate
- Prevents connecting to imposters
- Certificate authorities vouch for sites
Integrity
- Detects if data was modified
- Prevents tampering attacks
- Message Authentication Codes (MAC) verify content
The TLS Handshake
- Client Hello: Browser lists supported cipher suites
- Server Hello: Server chooses cipher, sends certificate
- Key Exchange: Both sides establish shared secret
- Secure Communication: All further data encrypted
TLS 1.3 Improvements
The latest version (TLS 1.3) brings:
- Faster connections: Reduced handshake round-trips
- Better security: Removed weak algorithms
- Forward secrecy: Mandatory, not optional
- Simpler protocol: Removed obsolete features
Checking TLS Security
Look for:
- TLS 1.2 or 1.3: Older versions are insecure
- Strong cipher suites: AES-GCM, ChaCha20
- Valid certificates: Not expired, trusted issuer
- HSTS: Forces HTTPS on future visits
Common Issues
- Mixed content: HTTPS page loading HTTP resources
- Expired certificates: Site hasn't renewed cert
- Self-signed certificates: Not verified by authority
- Downgrade attacks: Forcing older, weaker TLS
Related Terms
Certificate
A digital document that binds a cryptographic key to an identity (person, organization, or device). Certificates enable trusted encryption and verification—they're the foundation of HTTPS and secure communications.
Encryption
The process of converting information into a code to prevent unauthorized access. Encryption transforms readable data (plaintext) into an unreadable format (ciphertext) using a cryptographic algorithm and key. Only those with the correct key can decrypt and read the original data.
HTTPS
Hypertext Transfer Protocol Secure is the encrypted version of HTTP, the protocol used to transfer data between your browser and websites. HTTPS uses TLS encryption to protect the confidentiality and integrity of data in transit, preventing eavesdropping and tampering.