[n0ot]

Is this explicitly allowed? I've always thought it would be cool if amateurs were allowed to encrypt their communications, so long as they provided the decryption keys regularly over the same channel.

You could incorporate cryptographic signatures, diffie-helmann key exchanges, all kinds of fun stuff, and so long as you periodically transmit the decryption key, you're not hiding anything. I'm not sure what the legality of this is.

[throwaway3neu94]

It's thought to be legal but it is not explicitly allowed, and so it requires some legal interpretation and that is not court tested.