On: ‘Every message was copied to the police’

[generalizations]

> With a single key much smaller than a megabyte

Unless that was a preshared key, you're not talking about a one time pad. One time pads are inherently symmetric. If you're comparing symmetric to assymmetric crypto systems, you might as well just say that 'if my grandmother had wheels, she'd be a bicycle'.

[boloust → generalizations]

I don't think "symmetric cryptography" means what you think it means.

Stream ciphers and OTPs are both symmetric.

The "symmetric" part is the fact that the same key is used for encryption and decryption, not that the plaintext and key are the same length.