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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.


Dec
18
comment Attacks on the RSA Cryptosystem
This doesn't answer the question. There is, in fact, a specialized attack which allows one to factor N faster than testing all the missing bits when you have enough bits of $p$.
Dec
17
revised Can the encryption exponent e be greater than ϕ(N)?
deleted 1 characters in body
Dec
17
revised Can the encryption exponent e be greater than ϕ(N)?
added 222 characters in body
Dec
17
answered Can the encryption exponent e be greater than ϕ(N)?
Dec
17
comment Contruct a protocol to determine if three secret keys are different, without revealing any of them?
@ampersand I think it's not possible to do this strictly sequentially (i.e. last person to go announces results) without some sort of secret blinding, as anyone could interrupt the protocol and decide if the keys of all parties that have gone so far are different, ignoring the remaining parties. This would require the first person to blind the computation, and be given the final computation to announce the result. I am confident it can be done without leaking any secret keys, but it's not very clean..
Dec
17
comment Cracking WWII-era codes - code found on a pigeon's leg in Surrey
Some things are "uncrackable" even with infinite computing power.
Dec
16
comment Is there a big RSA Data Set
If you meant a list of all possible keypairs, this may help put things into perspective (by the way, saving $d$ is unnecessary if you already know $p$ and $q$ as it can be efficiently calculated from $e$).
Dec
15
comment creating a small number from a cryptographically secure random string
Well, yes, each number in the sequence is independent, but it may not immediately be obvious to one with little knowledge of probability why discarding a number and trying with the next (independent) one is a valid strategy. That's what I meant. By the way, did you make a typo with X < (N / K) * K? I think you meant X < K.
Dec
15
comment creating a small number from a cryptographically secure random string
Could you add a few words about why this is true? This might be of additional value to the OP, especially in cryptography you don't want to take anything for granted unless you have a proof or a solid reference.
Dec
15
comment security of Felix cipher
Yeah, the "crib" part was painful to read. Good answer though - those ciphers are nice for recreation and small messages, but they stand no chance in the context of modern cryptanalysis. And anyway, most ciphers are secure for sufficiently small messages.
Dec
15
comment Is there a field guide to ECC for the IT Security layman?
This is perhaps too many questions at once.
Dec
14
comment Deriving Keys for Symmetric Encryption and Authentication
@PaŭloEbermann Actually, CTR mode is defined for any sequence which does not repeat often, a counter is just the simplest way (and has maximal period). Incrementing by 3 is as valid as incrementing by 1 since $\gcd{(3, 2^n)} = 1$ but the usefulness of doing that is very arguable.
Dec
13
revised inverse element in Paillier cryptosystem
fixed probability
Dec
11
comment Contruct a protocol to determine if three secret keys are different, without revealing any of them?
@Sam When you say "If there are equal numbers between the three, this fact should be known, but no one shall discover which numbers are equal.", suppose A and B are the same age, do you mean it should be known that "there are two people in the group that have the same age", or that "A and B have the same age" (without disclosing their age, of course).
Dec
11
comment Can a shift cipher attain perfect secrecy?
Perhaps the exam referred to "shift cipher" as the textbook variant where each digit is encrypted with a different, independent key, which is really just a one-time-pad in disguise. I suggest this because the exam says "keys", whereas the traditional shift cipher has only one key. Not a very convincing argument, I agree, but otherwise, the exam is wrong and the correct answer is D.
Dec
11
comment How are primes generated for RSA?
Fast probabilistic testing is only half the answer, though. It's convenient primes are so dense at density $\frac{1}{\ln{n}}$, otherwise it wouldn't matter that we can check for primality quickly because we'd never actually pick a prime to check and validate.
Dec
10
comment inverse element in Paillier cryptosystem
@user4478 Yes, that is correct, but you can simplify this condition further - if gcd(a, b^2) = 1, then gcd(a, b) = 1 (can you see why?) and if gcd(a, b) = 1 then gcd(a^n, b) = 1 for all n.
Dec
9
comment Why is OCB-AES mode not becoming a standard for authenticated encryption?
OCB is patented for commercial use in the USA.
Dec
9
answered inverse element in Paillier cryptosystem
Dec
9
comment Public key cryptography - public key encrypts and cannot decrypt?
I think you meant $(m^e)^d \pmod{n} = m$.