163 reputation
10
bio website mirbsd.org/jupp.htm
location Germany
age 32
visits member for 1 year, 2 months
seen Nov 14 at 14:19

MirBSD founder (this includes mksh and jupp development), FreeWRT core team member (and casual contributor to its partial successor OpenADK and µClibc-ng), Debian Developer (Emeritus), Grml contributor) and doing lots of OSS work in general (virtually all C libraries, lots of porting, etc).

I hereby offer all content I author on the SO/StackExchange network also under The MirOS Licence (HTML version with less WTF-8) in addition to “cc-wiki” (CC-BY-SA 2.5 or 3.0, depending on the SO/SE network site, apparently). I urge everyone else contributing here to do the same.

English is only my third language, so please excuse any mistakes related to that I may make, e.g. when not fully awake. I do try.

Shortlink: Qs in my tags


Nov
14
comment Security analysis of Spritz?
One thing you may want to use Spritz over Keccak (besides ease of implementation) is that you can extremely easily switch between input and output modes. The STOP symbol is also nice. An RNG implementation will like that.
Nov
14
comment Security analysis of Spritz?
@ralph I disagree: simplicity of implementation can offset some performance loss. It’s about 33-50% as fast as RC4, in the setup I’d (probably will) use it (arc4random). Others have shown it’s still way faster than AES on the wire. Also, Keccak especially is ugly to use, and all others are if you have byte-sized input/output. And I really love to have a sponge for my RNG.
Nov
14
comment How should I treat a new cipher release like Spritz?
I’m excited but waiting… I can see it simplify the entire MirBSD entropy subsystem (beyond just arc4random).
Nov
8
comment Need 32-bit mixing function that has perfect avalanche between octets
Sorry, this is not appropriate, this has totally bad avalanche. But thanks for trying.
Jun
13
awarded  Announcer
Feb
8
awarded  Quorum
Jan
7
comment Relation between key size and PRNG state size
I’m not doing anything wrt. breaking crypto, my areas of interest lie elsewhere.
Jan
7
comment Relation between key size and PRNG state size
“I have also no idea why you say "160 bits of state is definitely not (enough) for a 1024-bit DSA key".” ← That is because DSA is weak in the face of bad entropy.
Jan
7
comment Relation between key size and PRNG state size
“that are effectively indistinguishable from random” does not mean that every bit is fully (1.000000) random
Jan
7
comment Relation between key size and PRNG state size
“Statements like "the quality of the output of the PRNG is debatable" is questionable; there exist high quality CSPRNGs” yes, but not all PRNGs are “high quality CSPRNGs”, that's what I meant, that the choice of RNG affects the answer.
Jan
7
awarded  Critic
Jan
6
comment Relation between key size and PRNG state size
@downvote: care to comment?
Jan
6
comment Random Number Generation with a Entropy pool versus Seed
You normally use both: a pool, to throw incoming events into, mix, and generate output from, and a seed, which is initially thrown into the pool (or just a dump of the initial pool, as in the MirBSD kernel).
Jan
6
answered Relation between key size and PRNG state size
Jan
6
comment At what stage is DHE and RSA used during the SSL/TLS handshake?
The problem here is that DHE needs good entropy on both sides, and that the DHE part is not secured by at least the server's key (or both parties' if they have some), to protect from casual eavesdroppers or the bad-entropy case. I'm currently considering switching to ephemeral RSA keys (short-lived, maybe a day or so) due to this, but have not yet tested whether this is portable enough.
Jan
2
awarded  Commentator
Jan
2
awarded  Scholar
Jan
2
accepted Need 32-bit mixing function that has perfect avalanche between octets
Jan
2
comment Need 32-bit mixing function that has perfect avalanche between octets
If anyone has got any comments left on the algorithm, or my implementation, of my use of it (to distribute entropy across multiple hashes), I will welcome feedback. I've credited this SE question in the CVS commit. (It's not yet “live” as I need to validate the “copy bytes around” part of my algorithm, but that is not the hard part. Just tedious.) Thanks!
Jan
2
comment Need 32-bit mixing function that has perfect avalanche between octets
I've not done a full test of my other criteria, only a random sample each, for the “keep 3 bytes the same and iterate the other in [00‥FF]” and “keep 2 bytes the same and iterate the other two in [0000‥FFFF]”. In both cases, every output byte had a perfect distribution across all 256 possible values, and in the second case, both the first and the second words had a perfect distribution across all 65536 possible values. I think that meets my criteria (except I didn't do it for all possible combinations).