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Jul
17
comment Given $g$, $b$, $g^{ab}$, is finding $g^a$ a hard problem?
Sorry for my unclear comment. It's is its and refers to the inverse of $b$ mod (p-1). Is $p$ unknown?
Jul
17
comment Given $g$, $b$, $g^{ab}$, is finding $g^a$ a hard problem?
I guess in $\mathbb{Z}_p$ after finding it's inverse
Jun
2
comment Reductionist proofs of decisional problems to computational
This is also another right-up towards this direction cseweb.ucsd.edu/~mihir/papers/gl.pdf
Jun
2
comment Reductionist proofs of decisional problems to computational
Thank you. Very educative and precise analysis
May
22
comment Security assessment between $g^{a_ix_i+r_i}$ and $g^{x_i+r_i}$
there is a relaxed security definition and the attacker is allowed to reveal the sum but not the individual values. There is no all-or-nothing definition...
May
21
comment Security assessment between $g^{a_ix_i+r_i}$ and $g^{x_i+r_i}$
The adversary doesn't know $x_i$
May
21
comment Security assessment between $g^{a_ix_i+r_i}$ and $g^{x_i+r_i}$
Nice question. $r_i$ is 'partially' secret. It is used to verify aggregate results. $g^{\sum{r_i}}$ is revealed
Apr
16
comment Existence of a map $\phi:\mathbb{Z}_{N^2}^* \mapsto \mathbb{F} $
@poncho. the multiplicative one: $\phi(ab)=\phi (a)\phi (b)$
Apr
16
comment Existence of a map $\phi:\mathbb{Z}_{N^2}^* \mapsto \mathbb{F} $
@fgrieu But from the isomorphism of the crt?
Apr
16
comment Existence of a map $\phi:\mathbb{Z}_{N^2}^* \mapsto \mathbb{F} $
If we assume finite fields defined over congruent classes of prime numbers then $|\mathbb{Z}_F|=F-1$ The order of $\mathbb{Z}_{N^2}^*$ is $N\phi(N)$. Maybe there is sth with the crt and the isomorphism $\phi: \mathbb{Z}_{N^2}^* \mapsto \mathbb{Z}_{p^2}^* \times \mathbb{Z}_{q^2}^*$ but $\mathbb{Z}_{p^2}^*$ and $\mathbb{Z}_{q^2}^*$ are not defined modulo a prime
Mar
18
comment Are there hash algorithms with variable length output?
@D.W. But is this secure?In the sense that there are only 360 possible values that can be brute forced easily
Mar
18
comment Are there hash algorithms with variable length output?
So what if i want a hash output that would range from $[0,360]$?If it was an integer then this is totally insecure as we need roughly 9bits. But can we extend the output from 9 bits to 160 by assuming that the integer part would always be 9 bits and then the other 151bits would be used for precision? And i do not care of hashing the same input to the same output.So it resembles that i am in need of a variable out pseudorandom generator
Feb
22
comment Can I safely replace XOR with ADD in a stream cipher?
So the only objective for the choice of the bitwise operation in a stream cipher is efficieny?Could we use birwise AND/OR as well?
Feb
11
comment Proofs by reduction and times of adversaries
There is a tighter reduction for RSA-FDH here: iacr.org/archive/crypto2000/18800229/18800229.pdf
Jan
30
comment Which blind signature schemes exist, and how do they compare?
I admire you for you patient to write so long analytical answers most of the time
Jan
30
comment Proofs of security methodologies
@mikeazo I don't agree very much with the categorization as the sequence of games are part of a more general category which is the indistinguishability game played between the attacker and the simulator-oracle (IND-CPA,IND-CCA,IND-CCA,)
Jan
21
comment What does it mean that $BW_N$ is a permutation over the squares mod N?
Suppose that you have a set of numbers $S$ in a specific order.Then randomly rearranging the elements means that you permute the elements.Now in a trapdoor permutation you have a key. Once you know the key you can reinverse the set in its original form.Suppose i.e that i permute by shifting one element at my right.This is the key.Now in your case the trapdoor of the permutation is the integer factorization problem.
Jan
18
comment How to ensure that a “received value” is not altered?
MAC considers a symmetric setting in which two clients have agreed on a secret key
Jan
16
comment Where can I find source code for ideal world simulation?
People from theoritical cryptography would commit suicide if they ever discover code for simulation based security
Jan
15
comment How to understand the Bilinear mapping with an example
You don't need to prove. You need to evaluate its correctness, i guess