Cryptography Essentials:

TSL vs SSL in a Nutshell


SSL (Secure Sockets Layer) and its successor, TLS (Transport Layer Security), are protocols for establishing authenticated and encrypted links between networked computers. Although the SSL protocol was deprecated with the release of TLS 1.0 in 1999, it is still common to refer to these related technologies as “SSL” or “SSL/TLS.” The most current version is TLS 1.3, defined in RFC 8446

SSL/TLS works by binding the identities of entities such as websites and companies to cryptographic key pairs via digital documents known as X.509 certificates. Each key pair consists of a private key and a public key. The private key is kept secure, and the public key can be widely distributed via a certificate.

The special mathematical relationship between the private and public keys in a pair mean that it is possible to use the public key to encrypt a message that can only be decrypted with the private key. Furthermore, the holder of the private key can use it to sign other digital documents (such as web pages), and anyone with the public key can verify this signature.

Via the SSL/TLS handshake, the private and public keys can be used with a publicly trusted certificate to negotiate an encrypted and authenticated communication session over the internet, even between two parties who have never met. This simple fact is the foundation of secure web browsing and electronic commerce as it is known today.


An SSL certificate (also known as a TLS or SSL/TLS certificate) is a digital document that binds the identity of a website to a cryptographic key pair consisting of a public key and a private key. The public key, included in the certificate, allows a web browser to initiate an encrypted communication session with a web server via the TLS and HTTPS protocols. The private key is kept secure on the server, and is used to digitally sign web pages and other documents (such as images and JavaScript files).

An SSL certificate also includes identifying information about a website, including its domain name and, optionally, identifying information about the site’s owner. If the web server’s SSL certificate is signed by a publicly trusted certificate authority (CA), like, digitally signed content from the server will be trusted by end users’ web browsers and operating systems as authentic.


Transport Layer Security (TLS), the successor of the now-deprecated Secure Sockets Layer (SSL), is a cryptographic protocol designed to provide communications security over a computer network. Several versions of the protocol are widely used in applications such as emailinstant messaging, and voice over IP, but its use as the Security layer in HTTPS remains the most publicly visible.

The TLS protocol aims primarily to provide privacy and data integrity between two or more communicating computer applications. It runs in the application layer of the Internet and is itself composed of two layers: the TLS record and the TLS handshake protocols.

TLS is a proposed Internet Engineering Task Force (IETF) standard, first defined in 1999, and the current version is TLS 1.3 defined in August 2018. TLS builds on the earlier SSL specifications (1994, 1995, 1996) developed by Netscape Communications for adding the HTTPS protocol to their Navigator web browser.

Public releases of SSL are deprecated in large part because of known security vulnerabilities in them. As such, SSL is not a fully secure protocol in 2019 and beyond. TLS, the more modern version of SSL, is secure.

History of TSL and SSL

We won’t be covering this part in detail but you are recommended to go through this video.