Is it possible to add a subject alternative name when converting PEM certificate to DER format.

openssl x509 -outform der -in Certificate.pem -out Certificate.der -extensions SAN -subject-alternative-name 'alternative name'

If possible, so how to make this operation with openssl?

1 Answer 1


No, of course not, this would change the certificate and invalidate the signature. You're asking the exact same thing as "I have a certificate for a domain I own, chedy.com, and I want to add google.com to the Subject Alt Names list, what is the openssl command for that?".

The difference between DER and PEM is just a base64 encoding.

You need to generate a new certificate with the SAN you want.

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