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Apr
4
comment Is it possible to create a “proof-of-upload” system for BitTorrent ratio tracking?
@JoeZ. : $\;\;\;$ The fact that "people participating in the torrent were required to register an account with the tracker" is part of the solution anyway. $\:$ I suppose if the use case you're thinking of has some way to sufficiently discourage the same person from holding multiple accounts, then that would simplify things. $\;\;\;\;\;\;$
Apr
4
comment Is it possible to create a “proof-of-upload” system for BitTorrent ratio tracking?
@user3100783 & Joe : $\;\;\;$ The tracker would fully direct who sends data to who. $\:$ Also, if the downloader is not a "throw-away account", then that attack is not quite as effective as it might seem at first glance, since the claimed downloader gets the amount added to it's total downloads. $\;\;\;\;\;\;$
Apr
4
awarded  Enlightened
Apr
4
awarded  Nice Answer
Apr
4
comment Is it possible to create a “proof-of-upload” system for BitTorrent ratio tracking?
The basic idea is that one proceeds somewhat like is described on pages 5 and 6 of this link, replacing "ordinary (non-verifiable) escrow of its signature" with "hybrid encryption of the data" and replacing "verifiable escrow of its signature" with "signature of the public-key part of the ciphertext and a Merkle hash of the rest of the ciphertext". $\:$ Trying to deal with dummy downloaders is a further mess involving proof-of-work and the tracker's own "test" downloaders. $\;\;\;\;$
Apr
4
comment Is it possible to create a “proof-of-upload” system for BitTorrent ratio tracking?
Actually, I now see that that pdf uses much more communication to achieve a much stronger security notion that is at all useful in this case. $\:$ I would have typed up a different solution, but it turns out that everything is a real mess to describe, what with the need to deal with dummy downloaders and describe tuples and that fact that I don't know whether or not BitTorrent's blocks use Merkle trees. $\;\;\;\;$
Apr
3
revised Homomorphic Encryption - Smart Vercauteren Batching
improved grammar
Apr
3
comment Is it possible to create a “proof-of-upload” system for BitTorrent ratio tracking?
citeseerx.ist.psu.edu/viewdoc/… $\;$
Apr
3
revised Traitor-tracing PRF
corrected minor issue
Apr
3
revised Key-dependent encryption in TAHOE-LAFS
inserted link
Apr
3
comment Private RSA key for HMAC key
I'm saying that it's more likely that there's some sort of non-trivial attack against that than against (uniform-key) HMAC. $\:$ If you nonetheless do that, then you should either use HKDF as described in this answer or take the middle bits, since I would expect the bias to be mainly in the high and low order bits. $\;\;\;\;$
Apr
3
answered What is the difference between PRF and a Random Oracle?
Apr
3
comment Private RSA key for HMAC key
Slightly what is probably the original one; mainly this more recent one. $\;$
Apr
3
comment Private RSA key for HMAC key
RSA private exponents are not uniformly distributed, which means the security arguments $\hspace{.92 in}$ for HMAC would not apply to using those as keys. $\;$
Apr
2
comment Private RSA key for HMAC key
One possible reason, that would of course be decisive, is if whatever you're coding in won't let you use an RSA private key as an HMAC key. $\:$ Have you checked that? $\;\;\;\;$
Apr
2
comment Private RSA key for HMAC key
No, although Https/SSL using a different key-pair would be an example of a channel that is authenticated in some other manner. $\;$
Apr
2
comment Private RSA key for HMAC key
The other way to know the public key is it being sent on its own, such as when the channel is authenticated in some other manner. $\;$
Apr
2
comment Private RSA key for HMAC key
@Stephen : $\;\;\;$ I'm guessing that Tyrsius already has the key-pair for some reason. $\:$ Otherwise, the proposal is silly in addition to possibly being insecure. $\;\;\;\;\;\;$
Apr
2
comment Private RSA key for HMAC key
The Certificate is not important for my question. $\:$ Whether or not the public key will be used for anything else is also not important for my question $\:$ Would the RSA "public" key be known to anyone else? $\hspace{.48 in}$
Apr
2
comment Private RSA key for HMAC key
Would the RSA "public" key also be kept secret? $\;$