IGCSE ICT 0417 - 8 Safety and Security

Objective: Know and understand digital certificates including its purpose and contents

This section provides detailed information about digital certificates, covering their purpose, contents, and importance in ensuring trust and security in the digital world. Understanding digital certificates is crucial for various online activities, including secure communication, verifying identities, and ensuring the authenticity of digital documents.

What is a Digital Certificate?

A digital certificate is an electronic document that verifies the identity of a website or individual. It's essentially a digital version of a passport, confirming that a website is who it claims to be and that the data exchanged with it is protected. Digital certificates are issued by trusted Certificate Authorities (CAs).

Purpose of Digital Certificates

Digital certificates serve several important purposes:

• Authentication: Verifies the identity of a website or user.
• Encryption: Enables secure communication by encrypting data transmitted between a web server and a browser.
• Data Integrity: Ensures that data has not been altered during transmission.
• Non-repudiation: Provides proof that a sender sent a message.

Contents of a Digital Certificate

A digital certificate typically contains the following information:

Field Name	Description
Subject	The name of the entity the certificate is issued to (e.g., a website domain or a person).
Issuer	The Certificate Authority (CA) that issued the certificate.
Serial Number	A unique identification number for the certificate.
Public Key	The public key of the certificate holder, used for encryption and verification.
Validity Period	The dates between which the certificate is valid.
Digital Signature of the CA	A digital signature from the CA, verifying the authenticity of the certificate.
Extensions	Additional information, such as permitted uses of the certificate.

How Digital Certificates Work

When you visit a secure website (indicated by 'https' in the address bar), your browser checks the website's digital certificate. The process involves:

1. The web server sends its digital certificate to your browser.
2. Your browser verifies the certificate's authenticity by checking the CA's digital signature.
3. If the certificate is valid and trusted, your browser trusts the website.
4. Your browser uses the public key in the certificate to establish a secure, encrypted connection with the web server.

Importance of Digital Certificates

Digital certificates are essential for:

• Protecting sensitive information transmitted over the internet.
• Building trust between users and websites.
• Verifying the authenticity of digital documents and software.
• Ensuring secure online transactions.

Certificate Authorities (CAs)

Certificate Authorities are trusted organizations that issue digital certificates. Examples of well-known CAs include Let's Encrypt, DigiCert, and GlobalSign. Browsers and operating systems have a list of trusted CAs pre-installed.

Checking a Digital Certificate

You can view the details of a digital certificate by clicking on the padlock icon in your browser's address bar and selecting "View Certificate" or a similar option. This will display the certificate's contents, allowing you to verify the issuer, validity period, and other details.