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May
1
answered Is the CONF key sharing Problem equivalent to discrete log problem?
Apr
29
comment Pseudocode for constant time modular exponentiation
You might have missed the "constant time" in the title (and also mentioned once more in the question). I don't blame you, because that wasn't emphasized in the question as it might have been, and the question didn't mention what prior research he'd done (a shortcoming of the question). But I don't think Alex Gaynor was looking for a generic description of the RSA algorithm; I think he was looking for a description of how to make a constant-time implementation of RSA. That said, I agree that the question could have been clearer.
Apr
29
revised Pseudocode for constant time modular exponentiation
added 171 characters in body
Apr
29
comment Pseudocode for constant time modular exponentiation
@figlesquidge, I beg to differ. It does answer the question (just not in way the author had expected). This is an XY problem: the author wants a constant-time RSA implementation (that's the X) and thinks the right approach is to implement it himself even though he doesn't understand the math (Y). I'm telling him that Y is not the answer to X; that the right answer is Z (use well-vetted code, or hire a cryptographer). P.S. "Don't do it" is a perfectly acceptable answer if you explain why: meta.stackexchange.com/q/8891/160917
Apr
29
comment Pseudocode for constant time modular exponentiation
@CodesInChaos, The fact that GnuPG failed does not mean that it is a good idea for a beginner who lacks a strong math background to try to implement RSA on their own. If the OP cannot understand mathematical descriptions of solutions to the problem, the OP probably shouldn't be trying to implement this himself (maybe he needs to hire a qualified cryptographer). Would you hire a random person off the street to design a bridge, if they told you they couldn't understand some of the core elements of bridge engineering (finite elements, differential equations, structural modeling)?
Apr
29
revised Can I make a PRNG that is secure even when state can be modified by user?
Fix a bug in the description of my attack. Simplify the description slightly.
Apr
29
answered Can I make a PRNG that is secure even when state can be modified by user?
Apr
29
accepted Multiple-prime RSA; how many primes can I use, for a 2048-bit modulus?
Apr
28
answered Pseudocode for constant time modular exponentiation
Apr
28
comment Simplified Key Wrapping to Achieve Only Confidentiality?
Ignoring authenticity/integrity is a really bad idea. It has led to successful attacks on confidentiality in the past. I strongly recommend against this sort of thing; use authenticated encryption or an authenticated key wrap algorithm that does provide integrity + authenticity.
Apr
26
comment Tiger Tree Hash vs generic Merkle Tree
Would you care to edit your question to define TTH? Maybe spell out the acronym, give a link, etc.? Also, I encourage you to describe what research you've already done to try to answer the question on your own.
Apr
26
comment Timestamping using a hashed linked list and public known events
@jliendo, I've edited my answer accordingly. The bottom line remains the same.
Apr
26
revised Timestamping using a hashed linked list and public known events
added 1060 characters in body
Apr
26
comment Zero-knowledge proof of a product
This is an excellent start, but it proves that $xy \equiv z \pmod q$, rather than that $xy=z$. I think if you choose $q$ to be $>2k$ bits long, and combine it with a range proof of the size of $x,y,z$, though, this might work. Thank you!
Apr
26
revised Zero-knowledge proof of a product
added 123 characters in body
Apr
26
comment Multiple-prime RSA; how many primes can I use, for a 2048-bit modulus?
@fgrieu, awesome, thank you for the detailed comments! Would you like to either create your own answer or to edit this answer into a form that addresses these issues? I'm not quite sure how to take into account the first issue you mention (about 1% chance of success), so would need help on that. Thank you again!
Apr
26
revised Multiple-prime RSA; how many primes can I use, for a 2048-bit modulus?
Incorporate comments from fgrieu
Apr
26
comment Can I prove set membership and uniqueness without revealing the element?
P.S. I see: the Wikipedia article on commitment schemes is a bit sucky, and it has led you astray. Wikipedia seems to imply that $C(x)=g^x$ is a commitment scheme, but in fact, that's not a good commitment scheme. The Wikipedia article does go to admit that such a scheme is not hiding, but it fails to connect the dots and realize this means that the scheme wasn't a (secure) commitment scheme after all, and thus does not make a good example of a commitment scheme. So, don't rely upon Wikipedia as your main source of information about commitment schemes.
Apr
26
comment Can I prove set membership and uniqueness without revealing the element?
@DrLecter, yeah, you definitely have a misconception about commitment schemes. $g^a$ is not a secure commitment to $a$. It is not hiding (neither computationally hiding nor information-theoretically hiding). As a result, it is not classified as a secure commitment scheme. A secure commitment scheme must be both binding and hiding. Therefore, what you are talking about is not a DL commitment -- it's not a commitment at all; it's just a broken thing that doesn't work. Of course, when I mention using a commitment scheme, I assume you use a secure commitment scheme, not something broken.
Apr
25
comment Can I prove set membership and uniqueness without revealing the element?
@DrLecter, I think you have a confusion/misconception about DL commitments. I'm not sure what specifically you have in mind when you mention "DL commitments", but any commitment scheme (whether information-theoretically hiding or computationally hiding) will conceal what was committed to -- nothing is leaked. It doesn't matter whether the value being committed to is low entropy or not; secure commitment schemes promise not to leak what was committed, even if the value has low entropy. If it's not hiding, it's not a secure commitment scheme. For instance, $C(x)=g^x$ isn't secure.