Right, but at a given air density, I'm pretty sure the v^2 relation holds. An airspeed of 400MPH would have 4x as much drag as you'd experience at an airspeed of 200MPH at the same altitude. So, you're both right--you just have to name which variables you're changing. :-)
I actually superheated a cup of coffee once in a microwave. I went to stir in some sweetner and it instantly boiled. About 3/4ths the coffee went all over the stove.
Yeah... Usually the first thing I do when I run an app that's skinnable/themeable (e.g. Mozilla, Firefox, etc.) I go look for the "Classic", "Plain", "Boring", "Native" or "I just work here, I'm not Gonzo" theme--whatever it might be called. If I can't find such a theme, I'm not likely to use the application much.
WinAmp is my favorite app to hate, with its micro-sized inscrutible icons. What, do its developers still run at 640x480 or 320x240?
Yes, many PRNGs can be wound forward/backward with some effort. That's where cryptographically strong hashes come in handy.
Linear Congruential and Linear Feedback Shift Register types I believe are particularly easy to attack this way. Lagged Fibonacci generators are also pretty bad.
Lagged Fibonacci generators are just LFSR's on steroids, if you look closely. The LSB is an LFSR, and the upper bits are LFSRs perturbed by the carries from the lower-order bits. Lagged Fibonacci generators are nice for some purposes, but I wouldn't use them for session keys. I use them for regression testing computational kernels against random test vectors, as they have exceptionally high periods. See Knuth, Vol 3.
I don't know what sort PGP used, but if PGP used one of those, tsk tsk.
Nowadays, programs should use a true entropy source (such as/dev/random) when it's available.
Or, more accurately, the asymmetric public key is used to encrypt/decrypt the "session key," which is the symmetric key. Typically, the session key's generated on the fly randomly. They don't get reused. The public key does.
That's why it was such a big deal when people found random number generator flaws in early SSL browsers. The session keys turned out to be rather predictable if you knew what time it was.
All a signature is is a one-way hash. If you want to verify the integrity of a message (not necessarily identify its author), you can do so by encrypting the message with a known key using cipher-block-chaining, and the last block doubles as a checksum for the whole message.
To verify identity with a symmetric cipher, you're back to needing a shared secret. In that case, substitute "known key" with "shared secret key".
Microsoft's spider hit me awhile back, computing all sorts of amusing math on this old CGI I wrote waaaaaay back when I was in college. Damn spider transfered nearly 60MB of HTML out of that CGI before it got bored and moved on.
I ended up explicitly adding it to my robots.txt file.
When I lived in Houston, there was an area that had what I call "Equal Punishment Lights." You'd be approaching the light, and as you near it, it goes from green to yellow to red. There'd be no traffic on the cross street. You'd sit and wait and wait, and then you'd see a car approach the intersection. The light goes yellow, then red for him, he stops, and I get the green.
Well, #5 there basically is saying "how much of this do we achieve through taxation (and thus wealth redistribution) and how much of this do we foist on those who can barely afford it?"
Hold on there professor. m^2 is METERs squared, not MILES squared. Miles are "mi". If I did my math right, there are about 2,589,988 square meters in a square mile. You're off by a factor of 2.6 million.
And 400 daylight hours per year? I guess we have to make due with 1 hour 5 minutes of light per day? Hardly. I'm pretty sure that 1kW/m^2 is a daily average.
When I correct your math, I come to: 295 billion kW for Arizona. (I use the definition "billion = 10^9".)
Now, assuming that 1kW/m^2 is an average number over an entire day, that means blanketing Arizona with collectors would give you about 2.6 million billion kWh per year. (s/million billion/quadrillion/ or s/million billion/10^15/ if you prefer.) There are about 8766 hours in a year.
Even if you say "oh, you only get on average 8 good sunlight hours, even that far south," fine. That's still around 1 x 10^15 kWh per year.
How does that stack up against our other energy sources again?
Right, but how often do you reboot a good workstation? Oh yeah... quarterly maintenance, if that.;-)
--Joe
Ya know, I used to get modded up all the time. I even had fairly high karma (well above the current cap) at the time they instituted the cap. Now I find it more relaxing just to drop the occasional trite comment. It's much more natural conversation. Oh, and I don't even display the scores on posts anymore. I just browse at 0. (I used to browse at -1, but even the populist, all-inclusive, bleeding heart left winger in me appreciates at least a little signal relative to the noise.)</rant>
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Right, but at a given air density, I'm pretty sure the v^2 relation holds. An airspeed of 400MPH would have 4x as much drag as you'd experience at an airspeed of 200MPH at the same altitude. So, you're both right--you just have to name which variables you're changing. :-)
--Joe... looks like my UID's prime ...
I actually superheated a cup of coffee once in a microwave. I went to stir in some sweetner and it instantly boiled. About 3/4ths the coffee went all over the stove.
--JoeNah, just "idiots." ;-)
--JoeMy wife's mom used to be a nurse. She said that at the hospital, they referred to motorcycle riders as "organ donors."
--JoeYou say that like it's a bad thing!
--JoeYeah... Usually the first thing I do when I run an app that's skinnable/themeable (e.g. Mozilla, Firefox, etc.) I go look for the "Classic", "Plain", "Boring", "Native" or "I just work here, I'm not Gonzo" theme--whatever it might be called. If I can't find such a theme, I'm not likely to use the application much.
WinAmp is my favorite app to hate, with its micro-sized inscrutible icons. What, do its developers still run at 640x480 or 320x240?
--JoeSorry, mine's not for sale.
But wasn't Bob Goatse's famous pic hosted on Apache? Oh wait, Apache doesn't use the GPL! Gotcha!
--JoeWhile you 5-digit IDs get all hot and bothered by a silly person with a 6-digit ID, us 4-digit ID users will sit back and chuckle.
At least, this one will. ;-)
--JoeYes, many PRNGs can be wound forward/backward with some effort. That's where cryptographically strong hashes come in handy.
Linear Congruential and Linear Feedback Shift Register types I believe are particularly easy to attack this way. Lagged Fibonacci generators are also pretty bad.
Lagged Fibonacci generators are just LFSR's on steroids, if you look closely. The LSB is an LFSR, and the upper bits are LFSRs perturbed by the carries from the lower-order bits. Lagged Fibonacci generators are nice for some purposes, but I wouldn't use them for session keys. I use them for regression testing computational kernels against random test vectors, as they have exceptionally high periods. See Knuth, Vol 3.
I don't know what sort PGP used, but if PGP used one of those, tsk tsk.
Nowadays, programs should use a true entropy source (such as /dev/random) when it's available.
--JoeProper grammar is contraindicated.
Or, more accurately, the asymmetric public key is used to encrypt/decrypt the "session key," which is the symmetric key. Typically, the session key's generated on the fly randomly. They don't get reused. The public key does.
That's why it was such a big deal when people found random number generator flaws in early SSL browsers. The session keys turned out to be rather predictable if you knew what time it was.
--JoeAll a signature is is a one-way hash. If you want to verify the integrity of a message (not necessarily identify its author), you can do so by encrypting the message with a known key using cipher-block-chaining, and the last block doubles as a checksum for the whole message.
To verify identity with a symmetric cipher, you're back to needing a shared secret. In that case, substitute "known key" with "shared secret key".
--JoeWell, because you hosed the grammar at "focus of core issues" (the "of" should be "on"), you get a stale MIT-MAGIC-COOKIE:
Bon appétit!
--JoeMicrosoft's spider hit me awhile back, computing all sorts of amusing math on this old CGI I wrote waaaaaay back when I was in college. Damn spider transfered nearly 60MB of HTML out of that CGI before it got bored and moved on.
I ended up explicitly adding it to my robots.txt file.
--Joeerrrr... I don't think there's anything in ANSI or ISO C that defines _start. When you say "conforming," do you mean "conforming to my system's ABI"?
--JoeActually, the code does not work fine on some compilers.
When I lived in Houston, there was an area that had what I call "Equal Punishment Lights." You'd be approaching the light, and as you near it, it goes from green to yellow to red. There'd be no traffic on the cross street. You'd sit and wait and wait, and then you'd see a car approach the intersection. The light goes yellow, then red for him, he stops, and I get the green.
It takes talent to time the lights that well.
--JoeEver see Space: 1999?
--JoeWell, #5 there basically is saying "how much of this do we achieve through taxation (and thus wealth redistribution) and how much of this do we foist on those who can barely afford it?"
--JoeHold on there professor. m^2 is METERs squared, not MILES squared. Miles are "mi". If I did my math right, there are about 2,589,988 square meters in a square mile. You're off by a factor of 2.6 million.
And 400 daylight hours per year? I guess we have to make due with 1 hour 5 minutes of light per day? Hardly. I'm pretty sure that 1kW/m^2 is a daily average.
When I correct your math, I come to: 295 billion kW for Arizona. (I use the definition "billion = 10^9".)
Now, assuming that 1kW/m^2 is an average number over an entire day, that means blanketing Arizona with collectors would give you about 2.6 million billion kWh per year. (s/million billion/quadrillion/ or s/million billion/10^15/ if you prefer.) There are about 8766 hours in a year.
Even if you say "oh, you only get on average 8 good sunlight hours, even that far south," fine. That's still around 1 x 10^15 kWh per year.
How does that stack up against our other energy sources again?
--JoeOh yeah. Exactly the same instruction set.
Oh, wait... MMX, SSE, SSE2... Also, oddball instructions like BSWAP and CMPXCHG8B.
Exact same instruction set. Gotcha.
I'm on the run... the cop got my gun... but right about now it's time to have some FUN!
/just saw the Beastie Boys on Saturday.
Right, but how often do you reboot a good workstation? Oh yeah... quarterly maintenance, if that. ;-)
--Joe