28,961 reputation
12156
bio website
location
age
visits member for 2 years, 11 months
seen 6 hours ago

Jul
3
answered Algorithm for computing square roots in $GF(2^n)$
Jul
3
comment Determine LFSR phase quickly?
@fgrieu: you've got it mostly; however there's one point you missed. When we're switching between $GF(2^k)$ representations, we're not actually changing anything essential in the equation. Instead, a "representation" is just a way of mapping between the elements of the abstract field to bit patterns; and yes, it is fun and easy to convert the bit pattern of one representation into the exact same field element in a different representation. Also, it doesn't matter of the generator is sparse or not; as long as it is primitive, the argument works.
Jul
3
comment Determine LFSR phase quickly?
@fgrieu: the $GF(2^k)$ argument can be used to address the later question; for two different polynomial representations of $GF(2^k)$, there is a linear mapping that preserves the field structure. Hence, we can use that mapping to map from the "hard" representation to the "easy" one, and solve it there. Now, the constant "2" in the hard representation will (probably) map to some other constant; if the easy solution depends on the base 2, we just solve two discrete logs in the easy representation.
Jul
2
answered Determine LFSR phase quickly?
Jul
2
comment After implementing a novel encryption algorithm, how would one go about analyzing its security or get help from others in doing so?
@NoctisSkytower: not off hand. You may find this shocking, but I'm not eager to attack a cipher from a newbee. Have you tried analyzing the cipher yourself? Have you looked into (for example) potential chosen ciphertext attacks (which is an easy place to start)?
Jul
1
reviewed Leave Open generate hash of all handshake messages for verify data (DTLS)
Jul
1
awarded  Nice Question
Jul
1
reviewed Close how to rememeber passwords securely?
Jun
30
reviewed Leave Open Pi Message Encryption
Jun
30
comment How to convert projective to jacobian co-ordinate in ECC?
@vijita: that reversed operation also preserves $DF^{-2}=AC^{-1}$ and $EF^{-3} = BC^{-1}$, and so, yes, those equations also "works".
Jun
30
comment Associative standard cryptographic hash function
Do you expect $H$ to be a cryptographical hash function, and in particular, have collision resistance? I ask, because if so, you'll need to take a lot of care in picking $F$; most of the associative functions we deal with in crypto are also commutitive at least much of the time; in this case, you want a function that hardly ever commutes; otherwise you can find $a, b$ with $H(a,b)=H(b,a)$.
Jun
29
reviewed Leave Open How to calculate inverse affine transform in AES from forward affine transform?
Jun
27
revised How to convert projective to jacobian co-ordinate in ECC?
added 51 characters in body
Jun
27
answered How to convert projective to jacobian co-ordinate in ECC?
Jun
27
comment RSA example-calculation: Public Key = Private Key (e = d)
Actually, the correct condition is $e > \sqrt{\lambda(n)}$. For a quick counterexample of your condition, consider $n = 2501$ and $e=11$. Here, $e=11 < \sqrt{\phi(n)} = \sqrt{2400}$
Jun
26
reviewed Leave Open moduli in SSL certificates
Jun
26
reviewed Approve suggested edit on How to decrypt 3DES in ECB mode (using a wordlist)?
Jun
26
reviewed Looks OK Testing hardware random number generators?
Jun
26
reviewed Delete Complexity class of an idealised version of Bitcoin's proof-of-work (hashcash)?
Jun
26
reviewed Close how to truncate a PRF on n bits to PRF on t bits where t < n?