Minor nitpick/correction: certificates are public keys, not decryption keys. Also you can only encrypt with a public key and decrypt with a private key or sign

Minor nitpick/correction: certificates are public keys, not decryption keys. Also you can only encrypt with a public key and decrypt with a private key or sign with a private key and verify with a public key. In general the CA PKI is mainly for endpoint (mainly server) authentication, actual encryption typically uses symmetric keys.