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comment Digital identification using steganography, can it be broken?
@Overloaded_Operator, I wouldn't assume anything about specific implementations until it's observed. Any aspect that deviates from a master copy may carry information. Examples: temporary change in audio balance; changes in video\audio bit-rates; dropping 1 frame at the end of a scene etc. The possibilities are basically endless. My answer used bit-strings to illustrate my reasoning. I certainly don't expect any real-world scheme to be this crude for a multitude of reasons. As a matter of fact, I have nearly zero knowledge about DRM schemes and was mostly thinking out loud ;-)
Dec
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comment Digital identification using steganography, can it be broken?
Agreed. In the answer I used $C_0$, $C_3$ and $C_4$ to create the 'rip'. The last bit in $R$ is a watermarked region, undetectable here because all three copies agree on that bit being 1; even though it's a 0 in the original master.
Dec
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comment Digital identification using steganography, can it be broken?
I've updated my answer based on what I think you mean, concluding that a smart watermarking scheme will be hard to beat.
Dec
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revised Digital identification using steganography, can it be broken?
Expanded answer
Dec
26
comment Digital identification using steganography, can it be broken?
Your statement 'Provided that original copies only differ in the watermarked regions' intrigues me, could you elaborate on that? Are you referring to different video features like frame-rate, bit-rate, resolution etc. or a watermarking scheme that defeats my 'naive' approach?
Dec
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answered Digital identification using steganography, can it be broken?
Dec
21
comment Is a Mersenne-twister cryptographically secure if I truncate the output?
@Greg, The observed numbers don't have to be a contiguous sequence for it to work. Even if an attacker would never be able to reduce the number of 'candidates' to one, he or she may have an edge because the Roulette wheel is no longer uniform from the attacker's perspective. Also, what would you use to generate the random numbers to randomly drop numbers from the MT?
Dec
20
comment Is a Mersenne-twister cryptographically secure if I truncate the output?
@Greg, it may be sufficient to reduce the search space by exploiting what you do know about the state. I had a thought: reseeding at fixed intervals (e.g. daily) may reduce security. The current and future state is ultimately determined by the seed. Assuming a 32-bit seed, I think the following is a practical attack: (1) collect a sequence of N rolls, (2) try all 2**32 possible seeds and maintain a list of best matches, by comparing the N observed values against X generated numbers. This can be done in parallel. Reseeding limits the search space (X) because it resets the state.
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Dec
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comment Is a Mersenne-twister cryptographically secure if I truncate the output?
@Greg, you say "If you have no information about the states (i+1) and (i+397) how can you find out what (i+624) will be?". If you know MT[i], you do have information about (i+1) and (i+397): it's 'embedded' in MT[i], because MT[i] is a function of MT[i+1] and MT[i+397].
Dec
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answered Is a Mersenne-twister cryptographically secure if I truncate the output?
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revised Why is it that researchers prefer finding secure software solutions over secure hardware solutions?
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answered Why is it that researchers prefer finding secure software solutions over secure hardware solutions?
Nov
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revised Appropriate AES key length for short term protection
Update.
Nov
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comment Appropriate AES key length for short term protection
I hate to pollute the comment section.. Would the combination AES with a Rabin Signature Scheme be a proper solution in my scenario? Both would persist for the whole session. Each message would be encrypted (AES) and the resulting ciphertext (ct) signed using RSS (s). A peer would send {ct, s} to all other peers.
Nov
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awarded  Scholar