How does SSL/TLS work?
Public key cryptography is a type of cryptography that uses two mathematically related keys: a public key and a private key. The public key is used to encrypt data, and the private key is used to decrypt data. Only the holder of the private key can decrypt data that has been encrypted with the corresponding public key. Symmetric key cryptography is a type of cryptography that uses a single key to encrypt and decrypt data. The same key must be used to encrypt and decrypt the data, so both parties must have the key before they can communicate securely.
SSL/TLS uses public key cryptography to establish a secure connection between two applications. Once the secure connection has been established, SSL/TLS uses symmetric key cryptography to encrypt the data that is being exchanged between the two applications.
Here is a step-by-step overview of how SSL/TLS works:
- The client application (such as a web browser) sends a request to the server application (such as a web server).
- The server application sends its public key to the client application.
- The client application generates a random session key and encrypts it with the server's public key.
- The client application sends the encrypted session key to the server application.
- The server application decrypts the session key with its private key.
- Both the client application and the server application use the session key to encrypt and decrypt the data that they are exchanging.
This process is known as the TLS handshake. Once the TLS handshake is complete, the two applications can communicate securely using the session key.
SSL/TLS also provides authentication, which helps to ensure that the two applications are communicating with each other and not with a third party. This is done using digital certificates. Such as an SSL/TLS certificate issued by emSign
When a client application connects to a server application, the server application sends its digital certificate to the client application. The client application then verifies the digital certificate with the CA (eg: emSign) that issued it.
If the digital certificate is valid, the client application knows that the server application is who it says it is. This helps to prevent man-in-the-middle attacks, where an attacker intercepts communication between two parties and impersonates one of them.
SSL/TLS is a complex protocol, but it is essential for protecting our data when we communicate online. It is used to protect our personal information, our email communications, and our online transactions.