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by doomrobo
2266 days ago
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All this is technically true. As long as you believe that you will never ever under any circumstance send the same video chunk twice under the same key, you get all the security guarantees of a real CPA-secure (=> non-deterministic) symmetric cipher. But 1. I don't think this is a reasonable belief, and 2. even if it is, why chance it when you can use CTR mode and a random nonce, with practically zero overhead? |
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Yes, that is the question here, and it's a really fascinating one. How often do you send two identical 128-bit chunks in practice? How much does it depend on the quality of your webcam and your lighting? If the video is grainy and splotchy in the background, you're getting a lot of randomness in your data. How much does that help? Any at all? Or are you still totally screwed?
> even if it is, why chance it when you can use CTR mode and a random nonce, with practically zero overhead?
1000 times this. Crypto code should be like the safety components in a car or an airplane. You wouldn't buy a car with seatbelts or brakes that work 90% or even 95% of the time. In the same way, you shouldn't write network code that probably doesn't let an adversary figure out everything you're sending.