TLS (Transport Layer Security)
TLS is a cryptographic protocol that ensures secure data transmission over a network. It is the basis of HTTPS and a replacement for the outdated SSL.
What is TLS in simple words
TLS (Transport Layer Security) is a cryptographic protocol that encrypts data when transmitted between two devices on a network. In simple words, TLS is a "secure tunnel" through which your data passes when you visit a website, send an email or pay for a purchase online.
Imagine that you send a letter by mail. Without TLS it is like an open postcard — any postman can read its contents. With TLS, the letter is sealed in an encrypted envelope that only the recipient can open. It is thanks to TLS that the padlock icon in the browser's address bar guarantees that your traffic is protected.
TLS is an evolution of the SSL (Secure Sockets Layer) protocol developed by Netscape in the 1990s. Modern SSL versions (2.0 and 3.0) are considered insecure and obsolete. TLS 1.0 appeared in 1999 as an improvement of SSL 3.0. Today it is recommended to use TLS 1.2 or TLS 1.3.
How TLS works
The process of establishing a TLS connection is called a "handshake" and includes several stages:
- Client Hello: The client (browser) sends the server a proposal of supported TLS versions, a set of ciphers and a random number.
- Server Hello: The server selects the appropriate TLS version and set of ciphers, sends its certificate and a random number.
- Certificate verification: The client checks the server certificate — whether it has expired, whether it was issued by a trusted certification authority, whether the domain matches.
- Key exchange: The client and server generate a common session key using asymmetric encryption (RSA, ECDHE).
- Encryption: All further data is encrypted with a symmetric algorithm (AES, ChaCha20) using the session key.
TLS versions
- TLS 1.0 (1999): Obsolete, contains vulnerabilities (BEAST). Not recommended.
- TLS 1.1 (2006): Improvements over 1.0, but also obsolete.
- TLS 1.2 (2008): Current standard. Supports modern algorithms (AES-GCM, ECDHE). Recommended.
- TLS 1.3 (2018): The fastest and most secure version. Simplified handshake (1-RTT instead of 2-RTT), no legacy algorithms.
TLS and HTTPS
HTTPS is HTTP over TLS. When you visit a site with HTTPS, your browser automatically establishes a TLS connection with the server. This provides confidentiality (no one can read the data), integrity (the data is not changed) and authenticity (you are communicating with a real server, not a fraudster). HTTPS requires a digital certificate issued by a trusted certification authority.
Frequently asked questions
What is TLS in simple words?
TLS is an encryption protocol that creates a secure channel between your browser and a website. Thanks to TLS, data (passwords, card numbers, messages) cannot be intercepted. The padlock icon in the address bar means that TLS is used.
How is TLS different from SSL?
SSL is a legacy protocol (1990s), TLS is its modern replacement. SSL contains known vulnerabilities and should not be used. TLS is an evolution of SSL with improved security and speed.
Which TLS version is the most secure?
TLS 1.3 is the most secure and fastest version. It speeds up the handshake, removes outdated algorithms and provides better protection. It is recommended to use TLS 1.2 at minimum.
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TLS (Transport Layer Security)
TLS is a cryptographic protocol that ensures secure data transmission over a network. It is the basis of HTTPS and a replacement for the outdated SSL.
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