What is a Digital Certificate?
A digital certificate is an electronic document used to prove the ownership of a public key. It is issued by a Certificate Authority (CA) and binds the public key with an entity (individual, organization, server, etc.).
Purpose and Use:
Digital certificates are primarily used in Public Key Infrastructure (PKI) systems to:
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Authenticate users, websites, or devices.
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Establish secure communications (e.g., HTTPS).
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Enable data encryption and digital signatures.
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Prevent man-in-the-middle (MITM) attacks.
How It Validates Authenticity:
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Issuance:
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A user or website generates a key pair (public and private).
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They send the public key to a trusted CA, which verifies the identity and issues a certificate.
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Validation Process:
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When a client (e.g., web browser) receives a certificate:
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It checks the CA’s digital signature on the certificate using the CA’s public key.
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Verifies that the certificate:
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Is issued by a trusted CA.
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Has not expired.
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Matches the domain or identity it’s supposed to represent.
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Is not revoked (via CRL or OCSP).
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Trust Chain:
- Browsers trust root CAs, which can validate intermediate CAs, and so on, forming a chain of trust.
X.509 Certificate Format is most commonly used format.
Conclusion
A digital certificate acts as a digital passport, proving the authenticity of a user’s or organization’s public key. Using the X.509 format, certificates ensure secure communication, user validation, and public key distribution in a trusted and verifiable manner.