Thomas
Reputation
4,885
Top tag
Next privilege 5,000 Rep.
Approve tag wiki edits
 1d comment Where is the mistake in my RSA by-hand calculation? For your second question about Python crashing, please see crypto.stackexchange.com/questions/13235/… 1d comment Where is the mistake in my RSA by-hand calculation? Your $d$ is wrong, it doesn't satisfy $ed \equiv 1 \pmod{\mathrm{lcm}(p - 1, q - 1)}$. In fact it doesn't even satisfy the weaker (but sufficient) condition $ed \equiv 1 \pmod{\varphi(n)}$. A working $d$ for $e = 17$ is 4235309647073. What calculator did you use? 2d comment Is it possible to combine two hash functions in such a way that cracking the constructed hash would require cracking the constituent hashes? What about C(password) = A(B(password) || password) where || is concatenation? I don't have time to prove it now but it appears to work around the issue you found with just composing the two hash functions. Apr 28 comment To what extent is WhatsApp's statement on secure messaging realistic? Agreed. If they did it honestly and correctly then end-to-end security is achievable, however they may be faking it with man-in-the-middle eavesdropping. This would be slightly foolish in that an independent team could check whether the public keys of two contacts match up (however the data may be obfuscated to make it hard to find out) but it would also be very naive to expect Whatsapp to not be data-mining all user-generated content. Also, even if the contents are encrypted, the metadata isn't and still carries significant information about you and your contacts; don't lose sight of that. Apr 17 answered A bijective hash function Apr 3 answered How is it possible that $g^q \equiv 1 \pmod p$ for a generator g? Apr 2 comment Are there any crypography schemes which rely on Graph Isomorphism not being in P? @BrentKirkpatrick You may want to read cstheory.stackexchange.com/questions/32237/… before putting faith in random papers on the internet :) Mar 13 awarded Enlightened Mar 13 awarded Nice Answer Mar 11 comment Implementing RSA with small integers in CUDA 128 bits is still not enough, so this doesn't really tell you anything. Mar 11 comment Implementing RSA with small integers in CUDA Crypto libraries are usually written in C, which also only has at most 64-bit native integers... how do they do it? Why not read the source of openssl or nacl to find out? Mar 8 comment Is this method of encryption theoretically unbreakable? @JPresperEckert Usually a CSPRNG means a deterministic algorithm that takes a small cryptographically secure seed as an input and returns a stream of pseudorandom bits. Are you saying your "CSPRNG" has no seed but returns truly random bits through atmospheric noise or whatever? Mar 8 answered Is this method of encryption theoretically unbreakable? Feb 21 comment Are checksums essentially non-secure versions of cryptographic hashes? @ArtjomB. A cryptographic hash truncated to 32 bits can easily collide with two inputs that differ in only one or two bits, whereas a CRC won't. The CRC is geared towards reliably detecting error patterns that commonly occur in transit, so it will do better on those kinds of errors and worse on others. The short hash does optimally over all inputs, and as a result does worse than CRC on the inputs CRC is good at dealing with. Feb 10 accepted Does key renewal increase complexity of MAC forgery? Feb 7 comment Does key renewal increase complexity of MAC forgery? Thanks for the answer! So assuming the MAC is not broken, are (1) and (2) the only possible best attacks, depending on whether or not the tag is shorter than the key? Jan 29 asked Does key renewal increase complexity of MAC forgery? Jan 26 awarded Yearling Jan 11 comment Is finding collisions in a part-hash not often enough a bad problem? It's not possible to get collisions "less often than expected" because I'm pretty sure this bound is the tightest possible over all probability distributions (being lowest for a uniform distribution). Either you are miscalculating the bound, or generating your values wrong, your results cannot be correct. Dec 15 awarded Enlightened