What is Certificate?
A digital document that binds a cryptographic key to an identity (person, organization, or device). Certificates enable trusted encryption and verification—they're the foundation of HTTPS and secure communications.
Also known as: Digital certificate, SSL certificate, X.509 certificate
Certificates create trust on the internet. When you see the padlock, a certificate is verifying that the website is who it claims to be.
How Certificates Work
- Certificate Authority (CA) verifies the entity's identity
- CA signs a certificate binding a public key to that identity
- Your browser trusts the CA and thus trusts the certificate
- TLS handshake uses the certificate to establish encrypted connection
What's In a Certificate
- Subject: Who the certificate is for (domain name, organization)
- Public key: Used to encrypt data to that entity
- Validity period: Start and end date
- Issuer: Which CA signed it
- Signature: Cryptographic proof the CA vouched for it
Certificate Types
- DV (Domain Validation): CA verified you control the domain—basic encryption
- OV (Organization Validation): CA verified the organization exists
- EV (Extended Validation): Stricter verification—green bar in old browsers
- Wildcard: Covers *.example.com
Privacy Considerations
- Certificate Transparency: Public logs of issued certificates—detect misissuance
- CAs see your traffic metadata: They know which sites requested certificates
- Let's Encrypt: Free, automated certificates—no payment/identity required for basic DV
Related Terms
Encryption
The process of converting information into a code to prevent unauthorized access. Encryption transforms readable data (plaintext) into an unreadable format (ciphertext) using a cryptographic algorithm and key. Only those with the correct key can decrypt and read the original data.
HTTPS
Hypertext Transfer Protocol Secure is the encrypted version of HTTP, the protocol used to transfer data between your browser and websites. HTTPS uses TLS encryption to protect the confidentiality and integrity of data in transit, preventing eavesdropping and tampering.
TLS
Transport Layer Security is a cryptographic protocol designed to provide secure communication over a computer network. TLS encrypts the connection between your browser and web servers, ensuring privacy and data integrity. It's the technology behind HTTPS.
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