CA Certificate
CA Certificate
A CA certificate, or Certificate Authority certificate, is a digital file used to verify the authenticity of other digital certificates, such as those that enable secure HTTPS connections. It is issued by a trusted organization known as a Certificate Authority
How CA certificates work
The CA certificate is the foundation of trust in a Public Key Infrastructure (PKI). Here’s how the process generally works:
- Verification: When a CA issues a digital certificate for a website, it validates the owner's identity and then cryptographically signs the certificate with the CA's own private key.
- Trust anchor: Browsers, operating systems, and other applications come pre-installed with a list of trusted CA root certificates. These root certificates are the highest level of trust in the chain.
- Validation: When a user's web browser connects to a secure site (indicated by "HTTPS"), the server sends its digital certificate. The browser checks if this certificate was signed by a CA it trusts. It does this by checking the signature against the CA's public key contained in the CA certificate it already holds.
- Secure connection: If the validation is successful, the browser trusts the website's identity and establishes a secure, encrypted connection. If the certificate is not signed by a trusted CA, the browser displays a security warning to the user.
Purposes of CA certificates
- Authentication: They serve as a credential to validate the identity of a website, person, or device.
- Encryption: They are essential for setting up encrypted communications over insecure networks, such as the internet.
- Integrity: They ensure that documents or messages signed with the certificate have not been altered in transit by a third party.
Root vs. intermediate CA certificates
The CA system is built on a hierarchy to enhance security:
- Root CA certificate: This is the top-level certificate in the trust chain. It is self-signed and stored securely offline. Its certificate is embedded in browsers and operating systems.
- Intermediate CA certificate: These are used to sign certificates for end-entities (like websites) rather than having the root CA do it directly. This minimizes the risk to the highly critical root certificate if an intermediate certificate is compromised.
CA certificates vs. self-signed certificates
It's important to distinguish between CA-signed certificates and self-signed certificates.
- CA certificate: Issued and signed by a trusted third-party Certificate Authority. It provides a high level of assurance and is automatically trusted by users' browsers.
- Self-signed certificate: Created and signed by the same entity that runs the server. It does not provide the same level of trust because there is no external verification. Browsers will typically display a warning when encountering one.
