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Security Fundamentals & Crypto · Foundational

Certificate Signing Request (CSR)

Message sent to a CA containing a public key and subject information, signed with the requester's private key.

Definition

A CSR (PKCS #10) proves possession of the private key and requests a certificate for the included identity. The private key never leaves the requester. The CA validates the request and returns a signed certificate.

Example

openssl req -new -newkey rsa:3072 -nodes -keyout site.key -out site.csr -subj '/CN=www.example.com'

Exam tip

The CSR contains the public key; the private key stays on the server.

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