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Mar
20
comment Soundness idea of basic zero knowledge prood
@DavidCash: no, I am saying that there are statements for which no ZKPoK exists, and one such statement is $\exists x: g^x = h$ (at least, we don't think so; if either the DLP and factorization problem is easier than we think, the above statement may be trivial). There does exist a ZKPoK proof that "I know such a value $x$", however that's not the statement that was originally claimed.
Mar
20
answered Soundness idea of basic zero knowledge prood
Mar
20
comment Soundness idea of basic zero knowledge prood
Zero knowledge proofs do not insist that a challenge be accepted only if the proposition being proved is true; in fact, they require that someone be able to generate a valid-looking transcript even if the proposition was false.
Mar
20
comment Is the term “Elliptic Curve Discrete Logarithm Problem” a misnomer?
@PGodbole: actually, we are being precise; ECDLP means the problem "given the EC points $G$, and $nG$, find $n$", and nothing else. What it is not is consistent; we talk about the elliptic curve operation as analogous to "addition" everywhere except for ECDLP.
Mar
19
comment Public-key based on roots of polynomial
With an infinite field, $P(x)$ may not be expressible in a fixed number of bits (or, depending on the field, even a bounded number of bits). That puts rather a crimp in the cryptographical applications.
Mar
19
comment Public-key based on roots of polynomial
Actually, it is easy to compute the roots of a polynomial $P(x)$ defined over a finite field.
Mar
18
revised Is the term “Elliptic Curve Discrete Logarithm Problem” a misnomer?
added 19 characters in body
Mar
18
revised Is the term “Elliptic Curve Discrete Logarithm Problem” a misnomer?
Minor corrections
Mar
18
answered Is the term “Elliptic Curve Discrete Logarithm Problem” a misnomer?
Mar
17
revised Meet in the middle attack - message and key
deleted 1 characters in body
Mar
17
answered Meet in the middle attack - message and key
Mar
17
revised Meet in the middle attack - message and key
edited tags
Mar
17
reviewed Reject suggested edit on Randomness test question from FIPS 140-1 and comparison with 140-2
Mar
17
comment Randomness test question from FIPS 140-1 and comparison with 140-2
I believe I got it correct; by making the test more stringent (that is, the acceptable range smaller), they made the probability of a good source being "out of range" (and hence failing the test) higher. For example, if a good source happened to have a monobit result of 10321, it would be accepted under 140-1, but rejected under 140-2.
Mar
17
comment Randomness test question from FIPS 140-1 and comparison with 140-2
As for the probability of failure with a good source, the monobit test is set for 5 standard deviations (FIPS 140-1) and 4 standard deviations (140-2). This implied a false failure probability from this test alone of 1 in 800,000 (140-1) or 1 in 8,000 (140-2)
Mar
17
comment Randomness test question from FIPS 140-1 and comparison with 140-2
The other thing to note is that with FIPS 140-2, there's only a handful of approved RNGs (RBGs); the ones listed in NIST SP 800-90, the X9.31 generator, one from 186-2 and the X9.62 generator. All these use cryptographical primitives, and may fail (that is, not provide sufficient unpredictability) if given insufficient entropy, but a statistical test will not catch that. Hence, there's nothing that these statistical tests bring to the table (plus these tests have a nontrivial probability of failing on a good stream)
Mar
16
comment Elliptic Curves of different forms
Actually, I believe P-256 cannot be made into a "safe curve" (at least, not without help from whoever selected the curve) because one of the requirements is "rigidity", that there are no unexplained constants involved, and P-256 (and the other NIST curves) have the constant $b$ that has not been explained.
Mar
15
answered Verifying multiplicative inverse on a prime field in NIST's ECDSA_Prime.pdf
Mar
15
answered RSA problem if i choose two specific small prime numbers?
Mar
15
awarded  Enlightened