If the key was randomly generated (not derived form a passphrase), it is impossible to crack the key. Usually when people talk about cracking a "key", they refe

If the key was randomly generated (not derived form a passphrase), it is impossible to crack the key. Usually when people talk about cracking a "key", they refer to brute forcing a passphrase that either protects the real key (encrypted wallet), or is used to derive the key (brainwallet).