2,586 reputation
415
bio website
location Leiden, Netherlands
age 19
visits member for 1 year, 6 months
seen Jun 30 at 13:47

Computer Science student and cryptography enthusiast.

You can contact me at orsonpeters@gmail.com.


May
1
comment Is AES still secure considering all this NSA/Snowden scandal?
@JW. Optimized code is more difficult to understand, that is correct. But there should be no excuse for "accidently branching ons secret data". It's very hard to justify any form of branching in crypto code, as often everything is unrolled anyway, and the very few places where you do branch should be on loops with arbitrary data length. There is no excuse for incorporating legacy code that does not follow the same design principles. These are the burdens you take onto you when you write crypto code, but that doesn't make it "hard", or "almost certainly broken with side channels".
Mar
14
comment How is a public key actually used to encrypt something?
@fgrieu I was only explaining to the asker how it would be possible to exponentiate a word document, I did not mean to suggest that it's either secure or practical.
Mar
12
comment How is a public key actually used to encrypt something?
@TylerDurden A form of encryption where you have a small shared secret (the private key - there is no public key), and use that small shared secret to encrypt any amount of data. Examples of such algorithms include AES, Salsa20, and more historic examples are Blowfish and (3)DES.
Feb
27
comment Non-standard signature security definition conforming ed25519 malleability
Another attack: github.com/jedisct1/libsodium/issues/112
Feb
11
comment How can we sign a contract digitally between two parties?
@RickyDemer Sadly, I have lost said device. Oh and I had written down the password on a post-it attached to the device. What a shame...
Feb
3
comment Is 80 bits of key size considered safe against brute force attacks?
This question appears to be off-topic because the crux of the question is opinion, because what you consider safe is different from someone else. And the nature of the question is not related to cryptography regardless - this is simply calculating the cost of an attack, basic math.
Jan
26
comment Can curve25519 keys be used with ed25519 keys?
@sellibitze Eehm maybe you misunderstood me, that was exactly my point.
Jan
24
comment Keeping IV secret for AES CFB mode
@DmitryKhovratovich Any "impossible to predict" algorithm, such as a random number generator, might also generate previously encrypted intermediate blocks as IVs. It's irrelevant to the choice of generating IVs - it's a weakness of CFB in general. But this is no reason to downvote my perfectly valid answer.
Jan
24
comment Keeping IV secret for AES CFB mode
@DmitryKhovratovich I don't think my answer is incorrect. I clearly stated in my answer that the IV may not be chosen by an attacker. So the attack "Consider, for instance, that you choose one of intermediate..." does not apply.
Jan
24
comment Can curve25519 keys be used with ed25519 keys?
@owlstead Sorry, I meant the cryptographers that develop the primitives themselves - they almost never release a Java library. There are a few "cryptography suites" as you've cited, that implement many primitives, but outside of those big suites there isn't much high-quality Java cryptography software available. This means that if you want to use modern cryptography, like Ed/Curve25519, ChaCha, Keccak, BLAKE, Poly1305, that you'll either have to implement it yourself or trust an often badly performing non-scrutinized third-party implementation.
Jan
22
comment Can curve25519 keys be used with ed25519 keys?
@Gracchus I think you should look into using a C library from Java - there are almost no cryptographers writing libraries in Java.
Jan
12
comment Methods of making ASIC/GPU resistant encryption?
What do you mean with "an encryption scheme", and please define how should it be resistant against ASIC's and GPU's (like what attacks should it be able to defeat)?
Jan
5
comment How can I solve congruence modulo N?
And in fact the statement should be the other way around, namely "finding $a$ is no harder than factoring $N$". Then as an interesting side note you may say that this is the fastest known method, but it is by no means proven optimal.
Jan
3
comment function of crypt called “ICE”
Then what is your question? The source code is freely available.
Jan
3
comment function of crypt called “ICE”
Have you, eehm, tried to google for ICE?
Jan
1
comment How can I solve congruence modulo N?
So did you mean $J_Aa^e \equiv 1 \mod n$, with $n = pq$, $1 < J_A < n$, $0 < e < n, gcd(e, (p-1)(q-1)) = 1$, $gcd(J_A, n) = 1$ and $a \in \mathbb{Z}$?
Jan
1
comment How can I solve congruence modulo N?
What are $J_A$ and $e$?
Dec
30
comment A timestamping authority (digital notary)
This service is a pretty popular one and has been up for a long time. It's not an "instant" API though, it uses emails and it seems to send your stamp at the end of the day.
Dec
30
comment Are hash trees an alternative, quantum-resistant signature scheme which can replace RSA?
@Reid I did some searching and found the paper. It's exactly what I remembered. Bernstein argues that BHT will never be superior to Grover's in price/performance thanks to the largely inferior memory usage. Running parallel instances of Grover is more cost effective, making BHT obsolete.
Dec
29
comment Are hash trees an alternative, quantum-resistant signature scheme which can replace RSA?
@Reid If I recall correctly Daniel Bernstein analyzed the two algorithms and concluded that no attack will ever be cheaper using Brassard-Hoyer-Tapp then Grover's due to the memory requirements, therefore only $2^{n/2}$ should be taken account for in terms of security levels.