A self-signed certificate cannot be trusted by your browser because it lacks the validation and verification process that is performed by a trusted Certificate Authority (CA). Let me explain why this is the case in detail.
Trust in certificates and secure connections on the internet is established through a hierarchical system. At the top of this hierarchy are the root CAs, which are trusted by default by all major web browsers and operating systems. These root CAs issue intermediate certificates to other CAs, and these intermediate CAs can then issue certificates to websites and other entities.
When you visit a website secured with HTTPS, your browser checks the digital certificate presented by the website to verify its authenticity. The certificate contains information about the website, including its public key. Your browser then uses the CA’s public key to verify the digital signature on the certificate. If the signature is valid and the certificate is issued by a trusted CA, your browser will trust the certificate and establish a secure connection.
A self-signed certificate, on the other hand, is not issued by a trusted CA. It is created and signed by the entity itself, hence the term “self-signed.” This means that the certificate lacks the validation and verification performed by a trusted third party. As a result, your browser does not have any reason to trust the self-signed certificate.
To illustrate this further, imagine you receive a document that claims to be signed by an important authority or organization. However, there is no way for you to verify the signature or the authority of the signer. In such a situation, you would naturally be skeptical and hesitant to trust the document. The same principle applies to self-signed certificates.
The lack of trust in self-signed certificates is a security measure implemented by web browsers to protect users from potential security risks. Without the validation process provided by trusted CAs, anyone can create a self-signed certificate and impersonate a website. This opens the door for attackers to intercept sensitive information, such as usernames, passwords, or financial details, by performing a man-in-the-middle attack.
While self-signed certificates can still provide encryption for data in transit, they do not offer the same level of trust and assurance as certificates issued by trusted CAs. This is why your browser displays a warning when encountering a self-signed certificate, alerting you to the potential risks involved.
In some situations, such as in a closed network or during development and testing, self-signed certificates may be used as a temporary measure. However, for public-facing websites and any scenario where trust is essential, it is crucial to obtain a certificate from a trusted CA to establish the necessary level of trust and security.
A self-signed certificate cannot be trusted because it lacks the validation and verification process performed by trusted Certificate Authorities. Your browser relies on this trust hierarchy to ensure the authenticity and integrity of secure connections. Without this validation, self-signed certificates open the door for potential security risks and are therefore not trusted by default.