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Comment by brianshaler | Hacker News Reader

It seems transmitting the raw sensor data would make it tricky to do this securely. Would it be possible to encrypt the signal with some sort of hardware cipher?

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They address the security possibilities in the paper:

> Our current implementation does not account for security. However, to secure the wireless link between the camera and reader, we can leverage the fact that our digital core processes the PWM signal. Each wireless camera can be assigned a unique pseudo random security key. Based on this key, the camera’s digital core can modulate the width of the PWM-encoded pixel value using an XOR gate. The reader, which knows the security key, can map the received data to the desired pixel values by performing the analogous operation.

XOR encryption with a mostly static image doesn’t seem very secure to me.

If the static image could be somehow "bankswitched", "shifted" or updated... I am thinking a huge one time pad. The problem is doing it power effeciently of course.

Thinking about, the main problem will be the penguin problem [1]. Which for a video is even worse as if a shape is moving, from seeing the pixels that are changing you can tell most of what is going on.

[1] https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation...

In my mind, strong encryption that can fend off the most serious attackers cannot apply to the analog part of the application.

However, analog scrambling techniques should still be effective in many cases.

It's XORed with a stream cipher, so it's totally secure (no part of the stream is reused).

The tricky bit might be deciding where to start the stream...

The transmitter and the receiver are in close proximity. Whatever transmitted, the eavesdropper can observe nearby anyway.

How about through a wall? That would make security applications in an apartment a bit less attractive, and I’m sure there are others. I wonder if encryption would be possible without much extra power overhead.

Some sort of directional shielding? Isn't backscattering light directional? Someone knows more about backscattering can have a better answer.

Analog encryption might be possible if the sender and receiver measure some common optical signal (assuming optically local security is what you're after).

Maybe, but good luck doing encryption without a power source.

There is a power source: the radio signal, but there's only microwatts available. Nevertheless, it's not impossible that there might be some clever solution to the problem, however, since the signal is analog that makes things a bit more challenging.

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