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location Waterloo, Canada
age 29
visits member for 3 years
seen Jan 20 '13 at 4:30

I am a PhD student with an interest in theoretical cryptography and mathematical tools used for cryptanalysis.


Feb
29
revised Is the $\ell$-Diffie Hellman Inversion easy when g is known?
added 234 characters in body
Feb
29
answered Is the $\ell$-Diffie Hellman Inversion easy when g is known?
Feb
19
revised Realize a MAC using a Pseudo-random function?
added 317 characters in body
Feb
18
answered Realize a MAC using a Pseudo-random function?
Feb
15
awarded  Enthusiast
Feb
4
comment How to account for moore's law in estimating time-to-crack?
Thanks for correcting me. I know these stuffs from theoretical point of view and to be honest, don't have much idea about practice.
Feb
4
answered How to account for moore's law in estimating time-to-crack?
Feb
1
comment Can md5 be used for encrypting data?
On the second paragraph, there has been a recent attack on finding collision on the MD5 with just single block. Since the method used in finding collision and second-preimage for MD5 were very closely related, I don't see any reason why the recent attack can't be molded properly to find even single block second preimage. So, there is good chance that a work will come that that finds another string that short that hashes to same value and it can be found pretty easily! I am quiet sure about that and hence skeptic about using MD5.
Feb
1
answered Can md5 be used for encrypting data?
Jan
30
comment Are there two known strings which have the same MD5 hash value?
I just saw it too on eprint and was about to post this one, but you beat me to that :)
Jan
30
comment Designing a key expander out of ciphers
I know this vulnerability, but you never mentioned that you want to use the same key for quiet a few time. Resilient function are usually Affine transformation, so they are vulnerable to attacks when there are more linear equations than the unknown. You can always use the idea that you have expanded keys which can be used in later state with the same set of ciphers (an idea which is like, not exactly but similar in vein to, bootstrapping from data-structure, not lie the construction of FHE). Resilient function are used in unconditional security (One time pad type vulnerability applies).
Jan
30
answered Proving knowledge of a preimage of a hash without disclosing it?
Jan
29
comment Proving knowledge of a preimage of a hash without disclosing it?
Lets discuss the question from more abstract level. We are given a hash function $h \in \mathcal{H}$, where $\mathcal{H}$ is a hash family. Can we prove something of the sort, given an output of the message and a hash function. I think this will find application in many places, especially identity based cryptosystems.
Jan
29
answered Can you help me understand ECC Cryptography and it's algorithm?
Jan
29
comment Proving knowledge of a preimage of a hash without disclosing it?
I went beyond what was in the talk. I think that considering a RO-model and solving this problem will be a theoretically great result.
Jan
28
comment RS Erasure Coding and Shamir's Secret Sharing
It is fine in that case because you can see that they are using two RS codes with two different parameters. The one with the erasure property has a weaker parameter than the one in the secret sharing scheme. We often use this form of composition while developing a protocol. You may find Kurosawa's work on "Error decodable secret sharing" (eprint.iacr.org/2009/263) and Martin et. al follow up work on "Error decodable secret sharing and one-round perfectly secure message transmission for general adversary structures" more interesting for a much stronger result.
Jan
28
comment Proving knowledge of a preimage of a hash without disclosing it?
I could not find any article that supported his talk in the rump session. Do you have an access to any such article. I would be very much interested in that because it sounds like a challenging problem especially when one sees hash function in the random oracle model. Maybe, then I could be of some help.
Jan
28
comment RS Erasure Coding and Shamir's Secret Sharing
I am sorry, I didn't check the link. You can use the RS code with the required parameter. They are equivalent in that case, especially because the unconditional security of Shamir Secret Sharing comes from the impossibility of solving a system of linear equations in $k$ variables with less than $k$ equations, or in other words, the Shannon theory of Perfect secrecy. The same holds for RS-code as well. You cannot decode a code if the hamming distance of the codewords received from any rightful code is more than the distance of the code. I hope this helps.
Jan
27
comment RS Erasure Coding and Shamir's Secret Sharing
I am not sure if any erasure code can be used to construct a secret sharing scheme. I would definitely like to see a reduction in that scenario. Reed Solomon has a direct relation with Secret Sharing if we see the space of all messages as the secret space and therefore, we have the bound. It is possibly for BCH also to show secret sharing property for the multivariate generalizations of Shamir-Secret sharing, but how to argue for codes, say like Reed Muller code or even Hamming code!
Jan
27
answered Current mathematics theory used in cryptography/coding theory