A certificate and a private key are two essential components in public key cryptography, especially in systems like HTTPS, TLS/SSL, email encryption, and authentication. Here’s a breakdown:
🔐 Private Key
- A secret key that must be kept confidential.
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Used to:
- Decrypt data encrypted with the corresponding public key.
- Sign data to prove authenticity and integrity.
- Example format: PEM (Base64-encoded, starts with
-----BEGIN PRIVATE KEY-----)
📄 Certificate
- A public document that contains the public key and identity information (e.g., domain name, organization).
- Issued and digitally signed by a Certificate Authority (CA).
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Used to:
- Prove the identity of a server or user.
- Encrypt data sent to the owner of the certificate.
- Example format: PEM (Base64-encoded, starts with
-----BEGIN CERTIFICATE-----)
🧩 Relationship
Example Use Case in HTTPS (TLS):
- Server sends its certificate to the client.
- Client verifies the certificate via trusted CAs.
- Client uses the public key in the certificate to encrypt a secret.
- Server uses its private key to decrypt that secret and establish a secure session.