How to download the certificate from a root CA? I need to the root CA certificate to close the certification validation chain.

If you know the CN (Common Name) of the root CA, for example "DigiCert High Assurance EV Root CA", you can search and download it our certificate database at certificate.fyicenter.com.

For "DigiCert High Assurance EV Root CA" root CA, you can download it here.

Or you can copy and save the following certificate text in a file called DigiCert.pem:

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

You can also go the DigiCert Root CA Web site to download it.

⇒ OpenSSL "verify -CAfile" - Specify Root CA Certificate

⇐ OpenSSL "verify -untrusted" - Specify Untrusted Certificate

⇑ OpenSSL "verify" Command

⇑⇑ OpenSSL Tutorials