Wikipedia:Reference desk/Archives/Computing/2013 June 12

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June 12

How to change the Internet Protocol packet default time-to-live in Linux?

What is the default, and how I can change it? Can the TTL of packages sent by a particular application be manipulated by the same application? Czech is Cyrillized (talk) 01:15, 12 June 2013 (UTC)

Use your systctl.conf. Simple google search reveals the answer. Shadowjams (talk) 02:53, 12 June 2013 (UTC)

And individual applications can modify it too - this is how traceroute works. Unilynx (talk) 20:45, 14 June 2013 (UTC)

Dual_EC_DRBG

I was wondering why Dual_EC_DRBG was included in the Template:Conspiracy theories. No one seems to deny the problems with the routine, or am I missing something? Ssscienccce (talk) 09:11, 12 June 2013 (UTC)

In his Wired article on the subject, Bruce Schneier says the weakness "can only be described a backdoor", and that of the badly chosen constants he says the NSA designers "had the mathematical opportunity to produce the constants and the secret numbers in tandem". He goes on "I don't understand why the NSA was so insistent about including Dual_EC_DRBG in the standard" and that "NIST and the NSA have some explaining to do". There's a general belief in the public cryptographic community that GCHQ and NSA are a decade or more ahead of academia in cryptographic research (as evidenced by both public key cryptography and differential cryptanalysis); so if NSA publishes something which turns out to have a weakness, those folks tend to suspect that NSA knew about the weakness all along. That's squarely a conspiracy theory; that doesn't mean there's actually a conspiracy - NSA are, after all, civil servants (with particularly weak oversight), and while secrecy can hide sexy James Bondism, it can also hide failure and incompetence. -- Finlay McWalterჷTalk 10:23, 12 June 2013 (UTC)

It's not wikipedia's role to define what is and what isn't a conspiracy theory. The article doesn't mention the phrase, there's no WP:RS saying it's a conspiracy theory. The routine contains a vulnerability, and IF someone has the key he can exploit that vulnerability. To quote Dan Shumow, Niels Ferguson:

WHAT WE ARE NOT SAYING:

NIST intentionally put a back door in this PRNG

• WHAT WE ARE SAYING:

The prediction resistance of this PRNG (as

presented in NIST SP800-90) is dependent on

solving one instance of the elliptic curve discrete

log problem.

(And we do not know if the algorithm designer

knew this before hand.)

And when Schneier says he's confused because it doesn't make sense in any way, that's pretty much the opposite of a conspiracy theory; a conspiracy to achieve nothing? Not exactly what the definition says: an explanatory proposition that accuses a person, group or organization of having caused or covered up an event or phenomenon of great social, political, or economic impact. Ssscienccce (talk) 13:00, 12 June 2013 (UTC)

Computer upgrades- thinking two steps ahead

I'm in the middle of upgrading (i.e. replacing most of) my five year old computer. I'm getting a lot of high powered new parts that'll hopefully be able to run all the advanced graphics software for my games and university course. However, I've hit a little bit of an issue, not so much a problem but a chance to plan ahead and see what would be the best, most economical solution. I can get a decent motherboard that'll do everything I want now, for about £50 or so, but when I want to upgrade further in a couple more years time, I'd need to replace that with a new, improved one. Or, I could get a much better motherboard, that'll handle everything I could possibly want from this thing for years to come, but would mean I'd have to upgrade to another AM3+ compatible CPU, if I don't want to have to replace it and waste all that extra cost. So, that'd mean risking quite a lot of money on there being a decent upgrade to my current CPU, that is hoping the Excavator chips have the same socket compatibility, assuming the project isn't cancelled entirely... And then I've been looking at these latest APUs, they seem to be going somewhere interesting...

So, do I stick with a big, powerful motherboard that I can upgrade bit by bit over many years, or get a cheap one that'll last me a couple of years and can be easily replaced when I come to embrace whatever new technology may be just around the corner?

213.104.128.16 (talk) 11:18, 12 June 2013 (UTC)

Personally I find that CPU, motherboard, and RAM form a triad, where to substantially upgrade one and not the others isn't cost effective, or just isn't possible (due to compatibility). The depreciation on computers and their part is so steep that I don't think it's ever worthwhile to buy something that significantly exceeds your current needs in the hope that it'll become necessary in the future. -- Finlay McWalterჷTalk 11:40, 12 June 2013 (UTC)

I concur. The only reference I can give is myself. I've been buying hardware (not only personal - corporate) for 20 years and I agree with Finlay. The only addition to that is to max out the RAM - or at least fill every slot with identical chips. It's really painful trying to find more RAM even 3 years down the road. 196.214.78.114 (talk) 12:09, 12 June 2013 (UTC)

This is worth a read. Highlights pros and cons is a general way - not too technical. It cautions that "a powerful, and expensive, graphics card isn't the magic bullet you might think". http://www.techradar.com/news/computing-components/is-it-worth-upgrading-your-old-pc-for-gaming-984617 196.214.78.114 (talk) 12:31, 12 June 2013 (UTC)

My advice is this: Don't ever buy the cutting edge stuff.

Here is why: If you buy the latest, greatest thing, it'll become the second greatest thing within some number of months. However, right now, it costs a lot more than the second greatest thing. Since your annual budget for PC upgrades is presumably finite, then if you buy the greatest thing, you'll have to wait longer before you can afford to upgrade it again. If you buy the cheaper, next-best thing - then you'll be able to upgrade it again sooner than if you'd bought the greatest thing. So if you were to plot a graph of how up-to-date your hardware is over time, it would look like this:

 *           *           *           *           *
   *         * *         * *         * *         *
     *       *   *       *   *       *   *       *
       *     *     *     *     *     *     *     *
         *   *       *   *       *   *       *   *
           * *         * *         * *         * *
             *           *           *           *

...where the vertical parts are when you do your upgrades. Now, by getting the second-greatest, slightly outdated hardware, the peaks are lower (because you never have the absolute latest stuff) - but because you saved money, you can upgrade sooner - before it gets as obsolete as your more expensive purchase - so the troughs are not as low and the frequency of that sawtooth is higher. The net effect depends on how fast hardware depreciates and how much you save by buying less-than-cutting-edge stuff - but even with quite conservative numbers, you have less obsolete hardware for more of the time by not buying the latest and greatest. Looked at another way, while you miss out on having the best hardware of all of your friends - you also miss out on having the lamest! SteveBaker (talk) 14:51, 14 June 2013 (UTC)

Excellent answer, Steve! That's always been my attitude towards the latest-and-greatest. Alternatively, you could buy the third best thing; though this is when you could run into outdated hardware issues... so definitely go for the strategy above. --Yellow1996 (talk) 01:30, 15 June 2013 (UTC)

I have flip-flopped on this. When I got my 80386, I went for the latest and greatest. It was so expensive that I had to use it 6-7 years. Then I started getting the second or third-greatest, more often. But it has gotten so incredibly difficult to migrate to a new Windows system that I want to delay that, and went to buying a good one that I can use for a long time. (You used to be able to just copy the files to the new computer. Now you have to track down all of the discs or files and reinstall them, install of the updates, and set all of your settings again.) Bubba73 ^{You talkin' to me?} 02:33, 15 June 2013 (UTC)

Yes, I can understand your frustration on that one. I use Linux - which runs very happily on ancient and recent hardware and can generally be upgraded without any of that fuss. I'm also increasingly finding that my computer is "good enough" - so the desire to upgrade has greatly dissipated! However, if you're a gamer, then I feel your pain! SteveBaker (talk) 14:16, 17 June 2013 (UTC)

I'm not a gamer - I use a lot of real applications. Bubba73 ^{You talkin' to me?} 00:04, 18 June 2013 (UTC)