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Nov
25
answered Elliptical curve cryptography key generation time
Nov
25
comment Elliptical curve cryptography key generation time
@ddddavidee: in this case, the naive algorithm (perform $d-1$ point additions) is so expensive that it can't even be done one.
Nov
24
answered what are multi-primes and how are they different from semiprimes?
Nov
24
comment Where to store the file extension to retrieve it correctly after decryption
If you don't need to keep the extension secret, the obvious alternative would be to keep that as a part of the filename. For example, you might encrypt the file 'test.pdf' as 'test.pdf.encrypt'.
Nov
24
reviewed No Action Needed How can two UProve token holders prove to a 3rd party that they aren't the same user?
Nov
24
reviewed No Action Needed El gamal correctness
Nov
24
reviewed No Action Needed Recovering El Gamal secret key from signatures
Nov
24
reviewed No Action Needed Blind Signatures
Nov
23
reviewed Leave Open Real life systems that use concepts of crypto computing
Nov
22
reviewed No Action Needed How does hash function in Elgamal signature scheme prevent existential forgery attack?
Nov
22
reviewed No Action Needed Addition / Multiplication modulo 13
Nov
22
reviewed No Action Needed Change of axis positions in Vigenere Square
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 Close Is there a Javascript and Java implementation of a good CSPRNG
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 $n$).