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visits member for 2 years, 7 months
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I am an undergraduate computer science and mathematics student in New Zealand. My fields of interest are computer graphics, in particular the physics of light transport, and to some extent cryptography, as well as programming and software development in general.


Sep
3
comment AES-ECB as an authentication mechanism
What is "Y" here? The ciphertext?
Aug
28
comment Is there a hash function which has no collisions?
@supercat and David you may want to create a chat room to discuss this (long comment chains like these tend to get automatically deleted after a bit)
Aug
9
awarded  Nice Answer
Aug
4
comment Theoretical attack on RSA
@Entimon If $p$ and $q$ are known to be close to one another, then, yes, it is fast (just like Fermat's algorithm), but if $p$ and $q$ are chosen properly (or even randomly, for sufficiently large $p$ and $q$) then $\lvert p - q \rvert$ is on the same order as $\sqrt{N}$, and in the same realm: infeasible.
Aug
1
revised Theoretical attack on RSA
fixed typo
Aug
1
revised Theoretical attack on RSA
added some notes and a bunch of links
Aug
1
answered Theoretical attack on RSA
Jul
26
comment Reversing DJB2 Hashes
Hint: I can tell you that the number I'm thinking of is even (0 modulo 2), that's not going to help you know if I'm thinking of 2, 4, or 34857188414. That information is lost when you reduce your input modulo 2^32, only the remainder remains, the original value is lost (yes, forever).
Jul
24
comment Low Public Exponent Attack for RSA
@CGFoX If you had only two congruences then your $n'$ would be on the order of $n^2$ (product of two moduli) and so your $m^3$ would be larger than $n^2$ (by an order of $n$) and you couldn't easily take the cube root without knowing the factorization of the moduli, so it doesn't work.
Jul
23
comment Which algorithm do you recommend for practical use to generate unique passwords for each website?
"If you go this route you are putting all your eggs in one basket. If you forget the master password, you lose all the derived ones. If someone guesses it, they can derive all the others." How is this any different than a password manager exactly? Or do you mean one of those online ones? And, yes, the master password must have quite a lot of entropy if you do this, at least 60 to 80 bits.
Jul
23
comment Which algorithm do you recommend for practical use to generate unique passwords for each website?
You should also consider password compromise (not the master secret, but individual passwords that you need to change for whatever reason). You could append a counter, or some other information that can be easily remembered and updated infrequently, if you don't want to store them, which I imagine is the whole point of the idea.
Jul
18
comment Given $g$, $b$, $g^{ab}$, is finding $g^a$ a hard problem?
@Loi.Luu 4 is in $Z_3$, it's just another representation of $1$. But unless $r$ is the order of $(Z_p)^*$, the math doesn't add up, as fkraiem showed above, and $g^x$ is no longer exponentiation but some other strange operation.
Jul
17
revised How to find which padding method is used in Block cipher(AES) encyption?
typo
Jul
17
answered How to find which padding method is used in Block cipher(AES) encyption?
Jul
15
comment Protocol: Coin Flipping over phone
It's not a one-to-one function, though - not even if $n$ is prime. You can see that it maps both $x$ and $-x$ to the same output value, so its range is at most half its domain (exactly half, if $n$ is prime - otherwise, quite a bit less depending on $p$ and $q$).
Jul
11
comment In RSA, why does $p$ have to be bigger than $q$ where $n=p \times q$?
You do realize that since $p \ne q$, one must be greater than the other, right?
Jul
3
comment Exactly two of the four roots must be greater than N/2
@habillqabill If this answers your question, would you consider accepting it by clicking on the check mark on the left?
Jul
3
comment Math to replace s-boxes - Good or bad idea?
I think you will find S-boxes are generally just not arbitrary permutations but often need to fulfill security properties such as resistance against linear/differential cryptanalysis (in the context of the ciphers they are used with) and not all S-boxes can be (reasonably) reached by your first algorithm, which means you also cannot efficiently "invert" the procedure to find $(p, q)$ from an arbitrary S-box, not even for 8-bit ones (perhaps it can be done if you add more degrees of freedom to your formula, but then you run the risk of being too expensive/vulnerable to side channel attacks).
Jul
2
awarded  Curious
Jul
2
reviewed Approve suggested edit on How do I choose the best 3*3 s-boxes?