2 ms·

I think most people would recommend symmetric encryption unless it now possible. With asymmetric keys each person still needs to protect their private keys.

• loup-vaillant 7y ago
  Let's say you deploy 100 or more IoT devices, and need them to communicate with your server. It's your server, so you can hard code a key in the devices. Now you have two choices: Choice 1: use a symmetric keys. This means one key per device, which you have to manage. Quite cumbersome. You could instead have one symmetric key for everyone, but then if only one IoT device gets compromised (which over time is a virtual certainty) the whole crypto system would be compromised. Choice 2: use a public/private key pairs. One for the server, and one for each device. Now the system is only broken when the server key is compromised. If a device gets compromise, the attacker merely learns the server's public key, and can impersonate that particular device. The main advantage of choice 2 vs choice 1 is that with Choice 2, you can use the same server key for everything. You'd still use a protocol with ephemeral keys, but you wouldn't have to manage many many keys. And if the IoT devices are untrusted (that is, they are assumed compromised or anonymous), the whole system only has to manage one key. Now sure, you could still make it more performant by retaining symmetric keys around. And you'd have to perform fast key erasure (replacing the key by a hash of the key) from time to time to ensure forward secrecy, but with public keys around the symmetric key can act as a cache, which can safely be erased whenever you restart or update your system.