What is TLS?

Transport Layer Security or TLS is a protocol that secures internet communications by encrypting the data transmitted between a client and a server. In addition, it can also secure the connection between two or more peers.

What is the Role of TLS in Securing Internet Communications?

TLS plays a key role in ensuring the privacy and security of data across a communication channel. It typically is used to accomplish the following:

1. Data Encryption:

When data is in transit between a web browser and a web server, the TLS protocol converts them into Ciphertext. These Ciphertexts can be decrypted into the original plaintext only with an authorized device that has the encryption key.

2. User Authentication:

TLS follows a certificate-based authentication. When a TLS handshake happens, the server and the client exchange their digital certificates containing identity info such as email address or domain name.

In addition, the certificate will also contain the public key for secure encryption of data and a digital signature from Certificate Authority (CA). Only when the certificate is valid and the signature is verified, the TLS allows the client to connect with the server.

3. Message Authentication:

Apart from verifying the peers, TLS also authenticates the message, to ensure that it is not tampered or forged during the transit. In this process, the sender calculates a message authentication code (MAC) in the form of a hash function and sends it with the data.

The recipient also calculates the MAC for the received data. In comparison, if both the sender and receiver MACs match, the TLS verifies that the message is authentic, otherwise it confirms that the message has been tampered.

Benefits of Transport Layer Security (TLS)

Confidentiality: TLS is solely responsible for the safety and privacy of data in transit. It cannot be read or modified by any third-parties.

Interoperability: TLS can work on almost all web browsers and operating systems.

Authentication: The clients, servers and the data undergoes verification during the communication, preventing any kind of man-in-the-middle attacks

Flexibility Of Algorithm: Algorithms for authentication, hashing and encryption can conveniently run on TLS sessions.

Ease of Use: Since TLS runs below the application layer, the client will not be able to see these security operations running in the app.

Forward Secrecy: Even if the private key of the server key gets compromised, the TLS ensures that the early sessions remain protected and cannot be subjected to vulnerabilities.

Integrity: Since the message authentication codes (MACs) verifies the data and authenticates it at both sender and receiver's end, it is guaranteed that the data has not been tampered in the transit.

Relay Protection: Since TLS uses timestamps and sequential order of numbers, it cannot be relayed by any third-parties.

Protocol Support: HTTP, IMAP and SMTP and many other protocols support the TLS encryption.

Main Components of Transport Layer Security (TLS)

Here is a list of the essential components of TLS and their corresponding functions:

Handshakes Protocol: Negotiates secure connection between the client and the server.

Alert Protocol: Notifies errors and warning messages

Record Protocol:: Encrypts data using the shared secret key

Random Number Generation: Generates random numeric values for the encryption keys.

Certificate-based Authentication: Uses a public-key infrastructure to authenticate the client and server involved in the communication.

Cipher Suites: Defines the algorithms for encryption and decryption of messages.

Key Agreement: Maintains the secrecy of messages transmitted between the client and server.

Key Derivation: Obtains the keys in the sender and receiver devices.

Key Update: Keeps updating the key until the connection is active

Message Authentication: Prevents message tampering during the transit

How Does TLS Work?

  • When your app or web browsers need to use Transport Layer Security Protocol, you'll first need to get a TLS certificate from the Certificate Authority (CA) and install it on your origin server. This certificate will have 2 primary information: Domain owner and server's public key.
  • When a user navigates across your TLS certified app/ website with, a handshake begins between the client device and the web server.
  • During the handshake, the following events occur: The TLS version for the session is decided, The type of cipher suites is selected, Server is authenticated, Session keys are generated for encrypting the messages.
  • For each session, the TLS handshake will choose a cipher suite containing the algorithms for encryption and privacy.
  • Next, it uses a public key cryptography to set the matching private and public key to the channel.
  • Following this, the protocol uses the public key to authenticate the server to the client.
  • Once the server authorization is done, the MAC verification is performed to authenticate and encrypt the data, at transit.
  • On delivery of the data, the recipient verifies the MAC, authenticates the server and decrypts the data into plain text.
  • This is how TLS completely takes care of the secure transmission of data over a communication channel.
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