[Cryptography] High volume thermal entropy from an iPhone

[Ray Dillinger]

On 12/14/2017 10:49 PM, Christian Huitema wrote:
> 
> 
> On 12/14/2017 5:06 PM, Jonathan Thornburg wrote:
>>> We have theoretical reason to believe that the dark signal from a phone camera is thermal noise.
>> Doing SecureCryptoHash(dark frame) is the easy part.
>>
>> The hard part is convincing yourself that that "dark frame" (which you
>> just got from some  ReadRawImage API is really "the dark signal" and
>> hasn't been processed either "helpfully" (i.e., in ways which would be
>> "helpful" for a typical phone picture) or maliciously.
> 
> In fact, I am not convinced at all that the "dark frame" approach is
> best. Camera vendors may very strive to make sure that the dark frame is
> actually dark. And it is also very easy to play games with an almost
> dark pictures, since your eyes will not notice the noise.

Have we any reason to suspect that whatever amount of thermal noise may
be present in dark frames, is not also present in photographs of actual
scenes with light and subjects?

If the question at issue is whether we expect thermal noise to randomly
flip some number of low-bits in the dark frames, I can't imagine a good
reason why that would not also happen to a camera in the course of its
intended use.

				Bear

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