What Is TLS Certificate? A Comprehensive Overview (2021)


With the recent cyber crime cases, it becomes imperative for ensuring the best means to transfer data for avoiding any sort of tampering or leakage of information. It is necessary for privacy and performance improvisation. TLS is the most reliable security protocol and has been widely accepted by many businesses for the secured transmission of data. TLS web connection requires a TLS certificate.

  1. What is TLS?
  2. What is a TLS Certificate?
  3. How does a TLS certificate work?
  4. Weaknesses of a TLS Certificate
  5. Trusting Certificate Authorities
  6. Special Precautions by ProtonMail

1.What is TLS?

TLS stands for Transport Layer Security. It is adopted as a security protocol for transmitting data online to facilitate end-to-end communications and online transactions. It ensures encrypting of data for communicating between web-based applications and servers. It can also be used for encrypting instant messaging, VOIP, e-mails. TLS protocol helps prevent forgery, hacking, eavesdropping, tampering of the messages, passwords, credit card credentials, data, personal correspondence being communicated across networks.

In the case of TLS vs SSL, TLS was proposed by Internet Engineering Task Force (IETF) in the year 1999 and SSL by Netscape. Many organizations are using TLS to ensure the secure transmission of sensitive data as they can multiplexing and demultiplexing services with guaranteed bandwidth.

2.What is a TLS Certificate?

A TLS certificate is a kind of digital certificate (or public key certificate/ identity certificate) issued by the Certificate Authority. The certifying authority authenticates the certificate by signing it, certifying that it belongs to a particular domain name which is the subject of the certificate. The details of the certificate include the subject domain name, organization, owner of the certificate, the public key of the server, which is essential for validation of the identity of the server, the certificate-issuing authority, issue and expiry date and many such details.

3.How does a TLS certificate work?

A TLS certificate consists of a public key and a private key that interacts behind the scenes during the transactions. They ensure secure encryption when someone visits a website. After receiving the directions for moving to a secured website, the TLS certificate and public key get shared with the client for secure connectivity and a unique session key. The browser then confirms the authenticity of the certifying authority and the status of the certificate.

The browser sends the symmetric key, and the server decrypts using his private key. This is then acknowledged by the server encrypted with a session key for starting the encrypted session. Thus this transmission of data with the session key helps in the privacy and integrity of the message.

TLS handshakes initiate when a user navigates to an application or website that uses TLS and is a multi-step process. This aids in authenticating the identity of the server, generation of sessions for TLS encryption of messages and establishes a cipher suite for the communication session. The protocols using handshakes with an asymmetric cipher establish better communication using a symmetric cipher.

With this, details of encryption or session keys will be used with the help of public-key cryptography. After the authentication and encryption of data and signature with the message authentication code, the recipient can authenticate for ensuring the integrity of the data. If any steps fail, then the handshake would fail to result in the connection not being created.                

4.Weaknesses of a TLS Certificate:

The greatest loophole existing in the digital era is of the hackers, intruders and cyber scams. TLS Certificate is also affected by them. A few of them are mentioned as under:

  • Poisoning the TLS certificate

If the computer gets attacked by malicious software, then the security of the TLS certificate is threatened. This would lead to the insertion of a root certificate which can cause responding to the user’s request fraudulently, impersonation of a website and gaining access to all the data.

  • Direct attacks on the Certifying Authority

A direct attack on the certifying authority could lead to unauthorized usage of the authorization keys.

  • Certificates issued by error

Users allow the certifying authority to authenticate the server for connection purposes. However, the vulnerability arises when the hackers exploit the certificate. This could lead to misuse of the certificate and compromising the connection issue on the server.

5.Trusting Certificate Authorities:

The setup of a CA consists of a Public Key Infrastructure that consists of many components like security infrastructure, auditing systems, practice statements, policy frameworks, all of which are essential for making the certificate secure and reliable. The model of PKI runs on two systems- root certificates and server certificates. If the root certificate is installed on your device’s certificate, it will be easily trusted by the browser. Similarly, every device has a local collection of root certificates from trusted CAs.

6.Special Precautions by ProtonMail:

Enhancing security and privacy has been the main aim of ProtonMail. Few additional measures are as follows:

  • DNS Certificate Authority Authorization (CAA)

When the instances of wrongly issued certificates came in, the need for DNS CAA was felt for blocking the issuing of wrong certificates. This aids in protection against misuse of the unintended certificate.

  • Certificate Transparency

The CAs post the certificates on the public log servers for validity and to prevent misusage.

  • TLS Certificate Pinning

This is a process for linking services to their specific public key. For validation, at least one element from the service matches with the elements in the pinset.


With the TLS security enhancement, the certificate is constantly updated with better versions, performance, TLS connection, and functionality. Several attempts have been made for revising the issues for addressing security concerns for defending the position against potential weaknesses. This aids in several benefits like ease of use, deployment, the flexibility of algorithm, interoperability and many more.

So, have you made up your mind to make a career in Cyber Security? Visit our Master Certificate in Cyber Security (Red Team) for further help. It is the first program in offensive technologies in India and allows learners to practice in a real-time simulated ecosystem, that will give them an edge in this competitive world.


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