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Jun
19
comment Cardinality of the key space $\{0,1\}^\ell$
Should $\:\{\hspace{-0.03 in}0,\hspace{-0.04 in}1\hspace{-0.04 in}\}^{\hspace{-0.02 in}10}\:$ be replaced with $1024$? $\;\;\;$ If no, what does your $<$ symbol mean? $\hspace{1.54 in}$
Jun
18
comment Encrypt a file for multiple persons with different keys?
Even if such schemes don't ordinarily allow that, one could let the "key material"s be tuples whose entries are reception keys and a broadcasting key. $\;$
Jun
18
comment Encrypt a file for multiple persons with different keys?
en.wikipedia.org/wiki/Broadcast_encryption $\;$
Jun
17
comment Establish Trust By Signing Random Seed
@MutantPlatypus : $\;\;\;$ One typically sets things up so that the client can verify that the given public key really was what the server choose. $\:$ That applies even if there are no trusted third parties, although you would presumably want to switch "client" with "server" in my previous sentence. $\;\;\;\;$
Jun
17
comment What is search space?
@sashank : $\;\;\;$ By going from $\:D1,\hspace{-0.02 in}D2,...,D6,\hspace{-0.02 in}D7\:$ to $\: D1\hspace{-0.03 in}$ || $D2\hspace{-0.02 in}$ || ... || $D6\hspace{-0.02 in}$ || $D7 \; $. $\hspace{1.59 in}$
Jun
17
revised What is search space?
improved grammar
Jun
17
comment Proof that two parties can communicate
@TessellatingHeckler : $\:$ That doesn't fit, since Alice and Bob could use the $\hspace{1.78 in}$ same "random"ness to generate the prime. $\;\;\;\;$
Jun
17
comment Proof that two parties can communicate
Yes. ${}{}{}\;$
Jun
17
comment Proof that two parties can communicate
One can choose PRNG seeds for Bob and Carol independently and uniformly, then give them both to each of Bob and Carol, so they can use the resulting bit-streams as their "random bits" and know what would've been sent along a Bob-Carol communications channel if there was one. $\;$
Jun
17
comment Proof that two parties can communicate
There is no such challenge. $\;$
Jun
16
comment pseudo random generator from length preserving one way function which is not permutation!
dash.harvard.edu/handle/1/4879174 $\;$
Jun
16
comment Securely start a client server connection without ssl/tls
What is it that the server [knows or [can do]] that the attacker [[doesn't know] or [can't do]]? $\:$ What is it that the client [knows or [can do]] that the attacker [[doesn't know] or [can't do]]? $\;\;\;\;$
Jun
15
comment Is there a scheme that allows to use RSA based challenge response protocol limited to signing only 8 bytes to create a secure signature of any data?
I'm actually talking about a very efficient special-case attack. $\;\;\;$ Namely, suppose that when $\: K = K_{\hspace{.02 in}0} \:$, $\:$ $P$ does not actually depend on $m$. $\;\;\;$ (After all, if there are PRFs then there are PRFs with that property.) $\;\;\;$ For such PRFs, 4 chosen queries to the device would allow production of signatures for all subsequently-determined messages, so although this would not constitute a forgery attack on your scheme, it does show that something more than PRFness of $P$ is needed for your scheme to "prove presence of the device". $\;\;\;\;\;\;\;\;$
Jun
15
comment Is there a scheme that allows to use RSA based challenge response protocol limited to signing only 8 bytes to create a secure signature of any data?
On the other hand, with $K$ predictable to an adversary, $P$ would need something like collision-resistance. $\;$
Jun
15
comment Is there a scheme that allows to use RSA based challenge response protocol limited to signing only 8 bytes to create a secure signature of any data?
Is your "securely prove presence of the device in a certain situation" idea quantitative or just qualitative? $\:$ For example, would it still work for your idea if an adversary could get signatures for $q^{\hspace{.03 in}5}$ messages with just $q$ queries to the device, for arbitrary positive integers $q$? $\;\;\;\;$
Jun
14
comment Why does UMAC encrypt the output of universal hash function?
In case you "have to skip the encryption step", the property which "would be required from the $\hspace{.44 in}$ universal hash function to make the scheme secure" is that the universal hash family be a secure MAC. $\hspace{.29 in}$
Jun
10
comment Is “Bit Independence” of SHA-2 hashes secure?
Is there some concatenation that you're not showing, or do you really have one thing called "secretKeyNonce256bit"? $\;$
Jun
8
comment Is it OK to encode data using key equal to data
@SOJPM : $\:$ No, since the OP's function does not take a key and anyone can evaluate it. $\hspace{1.04 in}$
Jun
7
comment Is it OK to encode data using key equal to data
No, his scheme tries to turn AES into a one-way function, not a Pseudo Random Function. $\;$
Jun
7
comment Is it OK to encode data using key equal to data
Your idea could also lead to collisions. $\;$