1,175 reputation
311
bio website redtwitz.com
location Paraguay
age 30
visits member for 2 years, 9 months
seen Jul 13 at 0:34

Mathematician. Power user. Coding enthusiast.

flair


Feb
24
comment Difference between Rijndael 128 / 256 blocksize implementations? (and impact of block size in general)
@figlesquidge: Uppercase B means bytes, not bits.
Jan
5
comment Deterministically combine more than one source of entropy
I'm not sure I know what you mean. Are you talking about deriving an integer from a pseudo-randomly generated floating point number or about the uniform distribution of the exclusive OR?
Jan
5
comment Deterministically combine more than one source of entropy
The sum of r1 and r2 will have an Irwin–Hall distribution, which is not at all uniform.
Dec
30
comment Why xor is a linear operation but ordinary adding is not
γ1 and γ2 can be any scalar, i.e, any element of the field F. In the example of the 8-bit integers, the only scalars are 0 and 1, yes. But in general, F could be any field, e.g., the set of all rational, real or complex numbers.
Dec
28
comment Why xor is a linear operation but ordinary adding is not
Right, scalar multiplication isn't distributive over field addition.
Dec
27
comment Using HMAC to secure a “widget”
HTTPS encrypts the GET request as well, not just the headers.
Dec
21
comment Brute Force on 3DES with Reduced Keyspace and Unknown IV
Do you anything about the second half of the key (e.g., it consists only of letters) or is it a pseudo-random string?
Dec
21
comment Brute Force on 3DES with Reduced Keyspace and Unknown IV
Do you know which mode of operation has been used? How long is the key?
Dec
17
comment Scrypt's maximum strength to increase entropy of lame passwords
@user4982: You can try to brute-force a password with pretty much every programmable electronic device with enough memory, but the estimated costs of the slides (and paper) use 2002 ASIC technology.
Dec
17
comment Is there a general method to crack this type of fractionating cipher?
How are spaces encoded?
Jan
4
comment Will length-extension work if secret is not prefixed but appended to the data?
No it isn't. But compared to, e.g., HMAC, it suffers from other flaws. See: Why is h(m||k) insecure?
Dec
20
comment Reason(s) for using a KDF for encryption keys
The output of a PBKDF2 implementation may be hexadecimal, but you can convert that output to whatever you want. Although, there are AES implementations that accept hexadecimal keys.
Dec
20
comment Double Encrypting with two different keys
It's important that the keys are actually independent, not just unique. To similar algorithms with related keys could go as far as canceling each other out, resulting in unencrypted plaintext.
Dec
16
comment creating a small number from a cryptographically secure random string
@fgrieu: That typo was a byproduct of the edit. Thanks. Which algorithm is the Best is relative. The algorithm provides randomness and is easy to implement, but it generates only 0.79 bits of output for every bit of input. (I assume that's what you mean by odds of failure.) Of course, if $x^2 \leq n$, the algorithm becomes rather inefficient.
Dec
15
comment creating a small number from a cryptographically secure random string
@neubert: See comment above.
Dec
15
comment creating a small number from a cryptographically secure random string
@Thomas: I see what you mean. I'll expand on that when I have a little more time. The division in X < (N / K) * K is integer division. If we were interested in integers below 100, we can use all X such that X < (256 / 100) * 100 = 2 * 100 = 200. With X < K, there would be no need for the modulus.
Dec
15
comment creating a small number from a cryptographically secure random string
@Thomas: I took this a premise, since the numbers of a random sequence should be completely independent, so it cannot matter which numbers we use (and in which order). But other than the quote each nameable subsequence of random sequence should be random as well from Infinity and the mind (hardly solid cryptography), I can't find any reference.
Oct
24
comment Is it feasible to build an index of prime factors?
@Hamidam: My point is that there are $2.42\cdot10^{533}$ times as many primes smaller than $2^{2048}$ than there are atoms in the observable universe. Unless we can store $2.42\cdot10^{533}$ bits of data in a single atom, it doesn't really matter what we're counting. The largest atom known to mankind is an isotope of Ununoctium that consists of 530 subatomic particles: 118 protons, 118 electrons and 294 neutrons.