Can we take a step back even further? I can't figure out the logic that got this started: "These Private Keys are stored in cold storage, for the purpose of r

Can we take a step back even further? I can't figure out the logic that got this started: "These Private Keys are stored in cold storage, for the purpose of revocation." Like what? Why? Since when do you need a private key to revoke a certificate? I feel like I understand certificates really well, but .. am I missing something?