Does a passphrase with high entropy provide the same level of security as the private key itself?
General scenario: An attacker has access to a private key file that is protected with a passphrase that has the highest entropy imaginable. Does this provide an advantage to the attacker?
A more concrete scenario: Synology offers a convenient cloud backup service to the users of the NAS systems: C2. It's protected with "AES-256 and RSA-2048 encryption". But: They also upload the private key into the cloud. To me this sounds alarming. But I actually can't judge if this makes any difference when choosing a passphrase with high entropy.