SSL

To compare a key, CSR or certificate to check they're related (e.g the CSR from key and the certificate is the signed CSR), generate the modulus for each item and they should all be the same.

For a certificate:

openssl x509 -noout -modulus -in file.crt

For a CSR:

openssl req -noout -modulus -in file.csr

For a key (assuming RSA):

openssl rsa -noout -modulus -in file.key

The output for each one is:

Modulus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