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Nov
21
comment CTR DRBG dependent on request size?
A library that implements DRBG-AES-CTR will implement AES-PRF, which can be used as a "chunkable" PRF.
Nov
21
comment CTR DRBG dependent on request size?
I respectfully disagree. A DRBG is not meant to be used as a PRF. It is only meant to generate bits that are to be used where ideally completely random bits should be used.
Oct
21
comment SSL implementation in windows?
I'm voting to close this question as off-topic because questions about programming, libraries and platform specific APIs may be asked on stackoverflow.com
Oct
8
comment How to show something is not a one-way function?
@fkraiem: I am saying that the condition "all polynomials $p$" in the definition of strong one-way function your answer, probably isn't what you meant. For all candidate functions, it is possible to choose a constant polynomial that makes the inequality false. Hence, no strong one-way functions exists.
Oct
8
comment How to show something is not a one-way function?
$p(n) = C$ is a polynomial.
Oct
7
comment Are there MD5 collisions for inputs of different length?
@ddddavidee: MD5 has an input length constraint of max $2^{64}-1$ bits. You can't have $2^{128}+1$ unique MD5 inputs each with a unique length.
Oct
7
comment How to find the value of a vector modulo a basis in lattice-based cryptography
Would it help to know that you will find the definition and a formula on page 12 of the paper? Cf: crypto.stanford.edu/craig/craig-thesis.pdf#22
Oct
5
comment Weird base64-like (?) encoding
Such encodings can be produced by any large arithmetics library that supports conversion of octet strings to integers and of integers to arbitrary base representation. It is however not on topic here.
Sep
26
comment Define “cryptographer”
People who state "I am not a cryptographer" in a question here, probably don't imply anything, but that they would appreciate an answer that only requires basic prior knowledge of the subject. Possibly, it might also be an appeal to the ego of any expert prepared to answer. Flattery is the simplest form of manipulation.
Sep
11
comment Encrypt with one cipher and decrypt with a different cipher?
Storing the algorithm in the ciphertext does not compromise security provided that the algorithm identifier is treated as additional authenticated data when the message authentication code is calculated.
Sep
7
comment What are the strenghts and weaknesses of Whirlpool Hashing Algorithm
This is not a weakness. It is a theoretical result that demonstrates that the number of rounds in the full algorithm can't be significantly reduced.
Sep
5
comment Is it possible to have E=D and Ke <> Kd?
Text book RSA fits the description: $E((N,x),t) = D((N,x),t) = t^x \bmod N$
Sep
2
comment Confusion regarding computing Multiplicative Inverse Modulo P?
$6 \times 2 = 2 \mod \phi(11)$.
Sep
1
comment POODLE attack on TLS 1.2
Technically, the Netscape formal specification of SSL 3.0 didn't specify how the padding should be generated. The SSL 3.0 specification is consistent with deterministic TLS 1.0 padding. A SSL 3.0 implementation that checks the padding is consequently consistent with the specification, but incompatible with a lot of implementations.
Aug
28
comment Key Size for Symmetric Homomorphic Encryption Over the Integers
You find the formula for the value of $\eta = \Theta \lambda log^2 \lambda$ later in the paper. $\lambda$ is the security parameter and $\Theta$ depends on the depth of operations to be supported.
Aug
26
comment Shamir Secret Sharing: Why cannot we recover polynomial's root if we have $t-1$ shares?
@mikeazo You forgot about the highest order coefficient. $k(x-2)(x-1)(x+1)$ has the same roots for any value of $k$. And if you don't know $k$, you can't calculate the constant term.
Aug
26
comment Shamir Secret Sharing: Why cannot we recover polynomial's root if we have $t-1$ shares?
Knowing all $t-1$ roots of polynomial of degree $t-1$, would still not be sufficient to deduce the constant term. The coefficient of degree $t-1$ will not show up knowing nothing but the roots, and this coefficient might have as many values as there are non-zero elements in the field.
Aug
21
comment Combine two sha512 hashes to a single hash
en.wikipedia.org/wiki/Length_extension_attack
Aug
18
comment Is calculating HMAC from hashed input a good idea?
Doesn't the fact that breaking HMAC generally requires a greater effort than finding a collision in the underlying hash algorithm, mean the answer is "yes"?
Aug
15
comment Anonymous offline digital cash scheme
The answer to the question, as currently worded, ought to be "no". Blind signatures are online by definition, so a digital cash system based on blind signatures can't be (completely) offline.