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Nov
21
comment Designing hash function in space-efficient identity based encryption
@hanu: I had assumed that you would generate a random looking value; one way would be to feed the id into a random number generator, generate $\log N + 64$ bits, and then take the result modulo $N$. However, as long as you generate values significantly larger than $\sqrt{N}$, it probably doesn't matter a great deal how you do it (as the squaring process is one-way if you don't know the factorization)
Nov
21
comment Designing hash function in space-efficient identity based encryption
@RickyDemer: well, given that the QR decisional problem is hard if you don't know the factorization, I suspect it might not matter if my method would generate only QR values (because someone else would not be able to distinguish anyways). Of course, that would depend a great deal on why you want values with Jacobi 1 in the first place.
Nov
21
reviewed Reviewed Python. RSA common modulus attack problem
Nov
21
comment Python. RSA common modulus attack problem
There are a couple of problems here (and I don't know Python well enough to give you the answers, hence this comment): a) to compute a 'negative power', you need to compute the modular inverse (and then apply the positive power); Python might provide such a utility, or as fgrieu said, you could do it on your own. b) you are using pow to compute the exponents; that is highly unlikely to work, as ME1^a is going to be huge (perhaps one trillion digits long); instead, you need to compute it modulo N (and again, Python might have a built-it to do that)
Nov
21
reviewed No Action Needed What Java actually stores inside Keystore when generating Keys?
Nov
21
reviewed No Action Needed java.util.Random and Dice Rolls
Nov
21
reviewed No Action Needed CBC-MAC, possible attack that violates computational resistance
Nov
21
reviewed Close Difference between signing with SHA256 vs. signing with RSA-SHA256
Nov
21
reviewed Close Is there a Javascript and Java implementation of a good CSPRNG
Nov
21
reviewed Close Problem description “SAFE”
Nov
21
comment Designing hash function in space-efficient identity based encryption
The obvious (and more efficient) way to come up with a value with a Jacobi of 1 would be to use a hash function to create a value between 1 and $n-1$ (relatively prime to $n$), and then square it (modulo $n$).
Nov
21
revised Hash collision using the leading 40-bits of SHA-1
Math correction
Nov
21
comment Hash collision using the leading 40-bits of SHA-1
@user1813580: why should you expect this logic to find a leading-bit collision within $2^{20}$ iterations; until it falls into a loop, it is effectively doing a random walk through bit patterns; and if you test $2^{20}$ random pairs for 40 bit collisions, you have probability about $2^{-20}$ of finding one. Once you run into a loop, then the bit patterns stop acting randomly (actually, independently), however (as above) you are quite unlikely to run into a loop that early.
Nov
20
answered Hash collision using the leading 40-bits of SHA-1
Nov
20
reviewed No Action Needed Are all binary-additive stream ciphers reciprocal?
Nov
20
comment What is the difference between order of base point and curve order in EC?
@Mhsz: close; it turns out that finite Elliptic Curves need not be cyclic; for example, they can have $Z_2 \times Z_2$ as a subgroup; however that turns out to be cryptographically unimportant, and everything else you said is correct.
Nov
20
revised What is the difference between order of base point and curve order in EC?
Readded a link to a related question
Nov
20
reviewed Approve suggested edit on What is the difference between order of base point and curve order in EC?
Nov
20
answered What is the difference between order of base point and curve order in EC?
Nov
20
comment What is the difference between order of base point and curve order in EC?
possible duplicate of Why would anyone use an elliptic curve with a cofactor > 1?