11,596 reputation
11049
bio website vyznev.net
location Helsinki, Finland
age
visits member for 2 years, 11 months
seen 1 hour ago

I'm a PhD student in biomathematics, working on stochastic individual-based models of evolution in spatially structured populations. My other interests include cryptography, programming games and puzzles, photography and graphic design.

I started programming (in AmigaBASIC) when I was 10 years old. Nowadays, I'm most comfortable using Perl, C and JavaScript. I know Java and PHP too, but I can't really say I like them. I also know some Python, but not as much as I'd like.


CC-Zero Please consider any (original) code I post to Stack Overflow and other Stack Exchange sites to be released under CC-Zero unless stated otherwise. You may do whatever you want with it and don't have to credit me in any way, although of course that would be nice.


I'm the main author and maintainer of the Stack Overflow Unofficial Patch (SOUP), a user script for browsers with GreaseMonkey-compatible user script support (Firefox, Chrome, Opera, possibly Safari) that fixes or works around a number of outstanding issues with the Stack Exchange user interface.

I tend to answer a lot more questions than I ask. Some answers I'm rather proud of:


Apr
23
comment What can I change in Lane to
Your question title appears to
Apr
15
comment Block cipher and parity of permutation
Generalizing your first example, if we start with any permutation, and extend the state space being permuted by at least one extra bit (which does not affect the permutation and is not affected by it), then the resulting extended permutation will be even.
Apr
1
comment What is h in the improved solution of RSA algorithm?
Ugh... I looked at the paper to try and fix the broken math formatting in the question, but it turns out to be like that in the paper too. :-( Honestly, most of the paper looks a lot like SCIgen output anyway.
Mar
23
comment Certificate signature with SHA-1 and RSA: where do 1888 bits come from?
See also identical question on security.SE.
Mar
23
comment Choice of reduction polynomial in Whirlpool's internal cipher
Ps. See also this related question.
Mar
23
comment Is this approach to generating a “random” number from a sha512 hash effective?
The list of participants' names might not have enough entropy to prevent you from cheating even without help from others. In particular, if you can guess who might sign up for the raffle (and in what order), you could compile a bunch of likely participant lists in advance, and, after testing a large number of possible secret inputs against those lists, select the one that has the best chance of giving you a favorable outcome if the actual participant list happens to match one of your guesses.
Mar
13
comment I need a 64-bit cryptographic hash for 96 bits of data
+1. The birthday bound is a harsh mistress.
Feb
20
comment How to represent a 32-byte SHA2 hash in the shortest possible string?
For case-insensitive file systems, it's probably best to stick with base 32 or 36, which can be encoded using single-case letters and numbers. In particular, the distinct printable ASCII characters allowed in Windows file names are not quite enough to encode six bits per character: there are 9 reserved characters and 26 equivalent upper/lowercase pairs, leaving only 60 usable characters (including space, which you don't seem to count; also, some file systems may have additional reserved characters).
Feb
13
comment Can someone explain the ECB Penguin?
@JoshBond: The "pattern" arises because pixels and cipher blocks don't line up exactly: an uncompressed true-color pixel takes up three bytes, while most common block ciphers encrypt blocks of either 8 or 16 bytes (64 or 128 bits).
Jan
30
comment Is the Couvreur et al. polynomial time attack on McEliece practical?
Hi, fractal, and welcome to Cryptography Stack Exchange! I've edited your question to add some detail and make it a better fit to our site. Please don't hesitate to correct any mistakes or omissions I may have introduced while doing so.
Jan
29
comment Avoiding overflow when encrypting with RSA
Also, just to clarify your last sentence above, the "flaws" for small $e$ (like Coppersmith's attack) only appear if one does not use a secure padding scheme (e.g. OAEP). With proper padding, RSA is secure even for $e=3$; without proper padding, it may not be secure for any $e$.
Jan
29
comment Efficient Robust Private Set Intersection Additive ElGamal
I just approved this edit suggestion from an anonymous user. (It still needs someone else to approve it.) I assume that was you? You might want to register an account here, so that you'll be able to edit your posts more easily.
Jan
14
comment Many time pad attack
@e-sushi: How does one attack a two-time pad (i.e. one time pad with key reuse)? would be a closer match; it even appears to be about the same Coursera exercise. This one's a little bit more specific, though, since the other question is about general solution methods while this one is specifically about the hint. (Also, the other question is kind of messy.) I wouldn't necessarily object to having them merged, but only if the questions are also edited to combine them.
Jan
12
comment Difference between CBC-MAC and CMAC
@figlesquidge: While the information requested probably is obtainable from Wikipedia, it's not very clearly presented there. IMO, this is a perfectly good reference question, and I'm hoping to see a concise and comprehensive answer summarizing the main differences.
Jan
3
comment Replay attack in ECB mode
@figlesquidge: Indeed. (Just to be clear, the fact that the link works is not a bug; I've reported the actual bug to SE privately, since it has (minor) security implications.)
Dec
28
comment Why xor is a linear operation but ordinary adding is not
Nitpick: the integers with ordinary addition modulo 256 are not a vector space over any finite field. In fact, they're not a vector space at all, although they are an abelian group, and therefore a module over the ring of integers.
Dec
27
comment How to attack this authentication protocol from “Cryptography: An introduction”
Ps. Where is this exercise from, anyway?
Dec
27
comment How to attack this authentication protocol from “Cryptography: An introduction”
possible duplicate of What does this Authentication protocol achieve and what information is shared?
Dec
27
comment Off-the-record communication
@RamRachum: No, because that would lose the deniability property we wanted in the first place: for a given $W' = W \oplus SHA(m) \oplus SHA(m')$, finding $Y'$ and $Z'$ such that $W' = H(Y' + Z')$ (for any meaning of $+$) would require breaking the preimage resistance of $H$.
Dec
25
comment Off-the-record communication
@RickyDemer: Good point. $\hspace{400px}$ But honestly, what's the deal with $\hspace{300px}$ the random $\hspace{240px}$ MathJax spaces, anyway? $\hspace{200px}$ $\hspace{200px}$ You know it doesn't really look the same $\hspace{100px}$ to anyone who doesn't have the exact same browser and fonts as you $\hspace{250px}$ anyway, right?