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Jun
25
comment Is algorithm with more than $2^{word size}$ words secure?
If you want a generic answer, then yes, it is believed to be possible to create a secure cipher (and assuming the block size is large does not invalidate that belief)
Jun
25
answered Is algorithm with more than $2^{word size}$ words secure?
Jun
25
reviewed No Action Needed Type of values that can be accumulated in bilinear map (multiplicative) accumulator reg.
Jun
24
answered NTRU less secure than previously thought?
Jun
24
reviewed Looks OK Why does an algorithm need a keyspace?
Jun
23
comment what are the most common stream ciphers algorithms?
@SEJPM: I deliberately left AES-CTR off the list, because it can be considered a block cipher (and also outputs 16 byte blocks, not 'bytes')
Jun
23
answered what are the most common stream ciphers algorithms?
Jun
23
comment Attack for RSA 1024 bit with Low Public Exponent
Actually, if the verifier only checks the lowest 16 bytes, then it's easy; pick a message with $x = MD5(Message)$ odd; and then find a 128 bit number $y$ with $y^3 = x \pmod{2^{128}}$ (which will exist if $x$ is odd, and can be found in 128 steps); then $y$ (zero padded) will be accepted as a signature for Message.
Jun
23
comment Attack for RSA 1024 bit with Low Public Exponent
Another conceivable approach: if the padding scheme was type 00, then if we could find an MD5 hash that's a perfect cube, that is, $MD5(Message) = x^3$ for some integer $x$, then the signature for that message would be the integer $x$ (zero padded). However, I don't know of a practical way to find a hash that yields a cube.
Jun
23
comment What is the danger if a non-prime is chosen for RSA?
@RickyDemer: hmmmm, I suspect that Shawe-Taylor could be extended so that it could generate a nontrivial fraction of the primes within the range, and still retain its provability and its relative efficiency (circa $O(n^{\lambda+1} polylog(n))$, where $\lambda$ is the exponent on a modular multiply). I believe that, if correct, would answer your question (as if you could factor the product of two of those with nontrivial probability, you could factor a hard product of two primes with nontrivial probability)
Jun
22
comment What is the danger if a non-prime is chosen for RSA?
And, there are certainly implementations that use provable primality techniques, such as Shawe-Taylor
Jun
22
awarded  Constituent
Jun
22
reviewed Leave Open Attack for RSA 1024 bit with Low Public Exponent
Jun
22
comment Implementing AES MixColumns with fewest XOR gates
At first glance, your code looks correct. Have you gone through the detailed test vectors, and see that the input into the invmixcol is correct, and that the output is not?
Jun
22
comment Implementing AES MixColumns with fewest XOR gates
I haven't gone through your question; however if you want to track down where in the algorithm you made mistakes, you may want to look at the detailed test vector in FIPS 197 (section A.1); that details the internal state after every single operations; it's invaluable in getting an AES implementation working.
Jun
22
reviewed Leave Open An example of Knapsack Cryptosystem cracks/attacks?
Jun
21
reviewed Close What is Polymorphic encryption?
Jun
21
comment Understanding Meet-in-the-Middle attack on block ciphers
Does your toy cipher consist of just the single round (precisely as you drew), or are there multiple rounds (each with a separete $K_i$)?
Jun
20
revised Stateless hash based public key cryptography?
added 32 characters in body
Jun
20
reviewed Close Any use for now-defunct Mt Gox Yubikey?