Heinlein's "Let There Be Light" (in the same collection of stories copyright 1950, although it was probably written earlier) is about an inventor who develops materials that convert electricity to light, and light to electricity, at high efficiency. The materials are cheap enough that solar power becomes essentially a free source of energy (and the story deals with how the established power-generation industries react to his invention; hint: they're not pleased).
I'm not sure exactly when it was written relative to the actual development of photovoltaic cells (used to generate power, not just as light sensors or physics experiments), electroluminescent backlights, LEDs, etc but it would be interesting to look it up.
Re:And what about...
on
Mapping Gravity
·
· Score: 3, Informative
"The frame of reference in which the microwave background radiation of the universe is stationary" Hmmm, I'm not a physicist & it's quite possible that this statement might mean somthing other then what one would logically assume it to buuuut - where might this be?
I think the original poster meant something like "the frame of reference in which the dipole anisotropy of the CMBR vanishes".
Right now, measurements of the microwave background radiation are blue-shifted in one direction and red-shifted in the opposite direction. If a spaceship left earth and accelerated toward the red-shift, it would eventually see the red- and blue-shifts disappear. You could then say that the spacecraft was "at rest" in the universe. However it gets more complicated when you have to consider the expansion of the universe - two distant observers can each be locally "at rest" yet they will have a relative velocity.
I also don't think that coliders are run 24/7 as someone else suggested / wrote.
Tell that to the grad students who are there at 2AM running experiments. I had a summer job at TRIUMF in Vancouver, and I can assure you that they don't just unplug the cyclotron at 5PM and go home.
I had to run a few shifts on one experiment that was shooting muons into cryogenic solids. Typical sequence:
- Collect data for 30 minutes
- Adjust temperature setpoint on the controller
- Go down to the experimental floor (involving various safety interlocks to ensure that the beamline is shut off before you open the door).
- Turn a liquid-helium valve just a little bit (this was the coarse temperature adjustment; the electric heater was the fine adjustment).
- Go back up to the data-collection room and press "start" (assuming you turned the valve by the right amount; if not go down and try again)
- Repeat until the sun comes up and they let you go home.
Particle physicists tend to be very good at Solitaire and Minesweeper.
Good. Now, the next time some "basic research" project like the SSC or a NASA planetary probe gets government funding, people won't be able to ask why their tax dollars are being "wasted on this %^#@$ instead of trying to find a cure for cancer" (and advances in genetically-modified foods should be able to get rid of the "... ending world hunger" one before too long too).
[Yeah I know, but my Karma's at 50 anyway, so go ahead and take your best shot...]
[Also, I remember reading about monoclonal antibodies in Discover or a similar publication back in the '80s. It doesn't appear to have been the miracle cure they thought it would be. Hope they have better luck making the jump from mouse to human this time]
so I poked around the chart of the nuclides to see how one would make Ac-225[...]But Ac-225 doesn't seem to have any such nice precursor decay paths with short half-lives.
I did a bit of web searching (with my CRC "Table of the Isotopes" handy), and it looks like the key is Uranium-233.
U-233 can be formed in a breeder reactor from Th-232, by: Th-232 + n -> Th-233 -> Pa-233 + e- -> U-233 + e-
Once you have the U-233, U-233 -> Th-229 + alpha -> Ra-225 + alpha -> Ac-225 + e-
This page at ORNL indicates they have a stockpile of 400kg of Uranium-233, and are "the only significant source of bismuth-213 [3 decays down from Ac-225, also useful for cancer treatment] in the western hemisphere".
I learned the correct pronunciation several years ago. I don't think they ever destroyed any of our packages, but there was one that came from the US up to Canada, got as far as our building (but not our office), circled around a bit, and ended up back in the US. We later found out they had tried to deliver it to another company down the hall, who had naturally refused to accept the shipment.
On the other hand, Oops did have a nice web tracking system so I could follow the adventures of this poor little package (which was a component we needed semi-urgently for a demo system). So they're not all bad.
p.s. Don't let them do the customs paperwork when you're bringing a package into Canada (slow and expensive, in my experience). Get your own customs broker.
Am I the only person on the planet who thinks that it's a bad idea to be sending so much coded E-M and junk hardware outsystem in order to make contact with aliens?
Greg Bear's The Forge of God and Anvil of Stars discuss this idea. Ships are designed for stealth, and Bad Things happen to a certain planet whose inhabitants weren't careful to shield their radio transmissions.
Plenty of today's PCMCIA NICs don't have dongles, e.g. Netgear FA411 (not an endorsement, just a remark).
Given that the thickness of a PCMCIA card is smaller than an RJ-45 plug, any PCMCIA NIC is going to need some kind of a kludge. The options I've seen are:
- Dongle
- "Pop-out" connector; cable plugs in vertically
- Double-height card (e.g. Xircom RBE-100)
Dongles suck, those little pop-out connectors just seem flimsy (and I have seen a couple of broken ones), and the double-height card is no good if your laptop only has 1 PCMCIA slot or you want to have 2 cards. It's much nicer just to have a real Ethernet port on the side of the laptop.
Another advantage of built-in Ethernet can be performance. Maybe this isn't an issue any more, but I seem to remember that in the early days a PCMCIA "100baseT" NIC couldn't get near 100 Mbits/second due to the limited bandwidth of the PCMCIA interface.
The problem I have noticed with the psyc's of physics teachers is they try to simplify the data to the students in an attempt to be hip... my high school professor called g 9.8m/s^2 where as my party school ECU professor in phys1000 called g 10m/s^2... this kind of thing bugs me a little.
10 m/s^2 is close enough for rough calculations. Often it's more important to illustrate some general principle, rather than to come up with an "exact" number. Even 9.8 is an approximation (the 1986 CODATA recommended value is 9.80665), and 'g' isn't even a constant - it depends where you are on the earth (and on other factors).
I looked up neutrino last night online and the def was short: a particle that has no mass and who's charge is neutral.
Find a better reference. There's some material here that looks like it might be decent. I've seen better pages, but I don't have the bookmarks handy.
No charge - correct. However, as the article mentions, recent experiments indicate that neutrinos have some mass. They also have spin 1/2, like electrons.
are very fast
This is related to mass. If they had zero mass, they would travel at the speed of light (like photons, which have no rest mass). However, if they do have mass, then they have to travel at slightly less than the speed of light.
Supernova observations can be used to estimate neutrino mass, by measuring the time difference between the arrival of visible light from the supernova, and the arrival of a neutrino pulse. Over those vast distances, even a very small difference in speed could lead to a significant difference in arrival times.
and pass through the planet so fast most detection has to be done underground...
This is a bit off. The interesting item is that most neutrinos pass right through the planet without interacting with any atoms. Because they interact so weakly with matter, a detector will only see a very small number of events caused by neutrinos, even though there are bazillions of neutrinos passing through it every second.
However, a detector on the surface of the earth would also see events not from neutrinos, but from other cosmic radiation like muons (actually, muons generated in the upper atmosphere by cosmic radiation). Going deep underground blocks out all particles except neutrinos, enabling the experimenters to get accurate measurements.
It is actually quite normal for planes to crash every now and then, therefore it is most likely to be an accident.
A good example to support this point is the Sibir Airlines plane that went down in the Black Sea a month ago. Initially it was assumed to be terrorism (especially since the plane departed from Israel). However the consensus is now that it was hit by a stray Ukrainian missile that got away from its test range.
So even though terrorism might be the most likely reason for the New York crash, and the first thing that should be investigated, it is not the only possibility.
or some reason I was thinking about those who were tried & convicted. I believe that if it has been proven that you are indeed guilty of committing a crime, you have no rights.
That's a load of crap, for two reasons.
1) Wrongful convictions. If you look here you will see several cases of people jailed for murder, and released years later when they were found to have been innocent of that crime (thanks to advances like DNA testing). These are Canadian cases, but I'm sure there are American examples as well; hopefully they all lived long enough to take advantage of their overturned conviction.
2) Bad or arbitrary laws. People can be locked up in one area for behaviour that is perfectly acceptable in another area (e.g. drug and alcohol laws in Netherlands vs. USA vs. Saudi Arabia, the Dmitry/DMCA thing, or those quaint areas where certain sexual acts between consenting adults are illegal).
In both cases, I believe the person involved does NOT automatically lose all of his rights once he's convicted. The person in the first case has a right to say "I didn't commit this crime", and the person in the second case has a right to say "What I did shouldn't be a crime". Take those rights away, and you're heading down a *very* slippery slope. [rather than invoke Godwin's law, I'll stop here]
My personal paranoia and suspicions aside, who would sell their HD to a stranger *without* first wiping the disk?
Well, a local dot-com went out of business recently, and auctioned off almost all of their corporate and development servers (including the Visual SourceSafe repository) without wiping the drives. I've also bought an un-wiped computer from a consignment shop. So I wouldn't automatically assume that the laptop in question was stolen.
Would an attack to MD5 all known IP addresses be trivial, or extremely difficult?
There are at most 2^32 possible IPv4 addresses (fewer once all the "special" ranges like 127/8 and multicast are taken out). MD5 produces a 128-bit (16-byte) hash, and an IP address can be stored in 4 bytes.
You could construct a lookup table with 20 columns (16 bytes for the hash, and 4 for the IP address that produced it) and 2^32 rows. That's about 85GB - a consumer-level hard drive, these days.
Generating the table wouldn't take much time (I'd guess a few hours) and would only need to be done once. So I'd rate this as an "easy" dictionary attack.
Now if a random salt value was hashed along with each possible IP address, you'd have to re-generate the entire 85GB table for each salt value. So this would make the attack more difficult, but it would still be possible to recover several IP addresses per day on a regular PC.
A black hole without the "doughnut" of hot matter is not in conflict with current theory, if it is massive enough.
But according to the article, this black hole *does* have the hot accretion disk (as well as a huge jet blasting out of it). The missing "doughnut" is cooler matter (emitting in infrared, not X-rays) that they expected to find around the disk.
I think (but I'm too lazy to check) that there's a picture in the Kip Thorne book you mentioned showing a few possible theories for what the gas around a black hole could look like, with a variety of electric and magnetic field patterns. So this "no doughnut" observation will probably help to refine those calculations, but I don't see it overturning any fundamental black-hole concepts.
if it's a truely random key (hard to find) then there are no patterns to take advantage of. it's unbeatable.
If it's not a truely random key, it's not a one-time pad (in the standard sense) but rather some type of stream cipher.
A stream cipher uses a keyed mathematical algorithm to generate a stream of data that "looks random" but of course is completely deterministic. This keystream is then XOR-ed with the plaintext, as in the OTP.
I find it helps to think of the one-time pad as "secret splitting" - you take the original plaintext, and divide it into two halves (the random keystream, and the keystream XOR the plaintext). Neither half by itself tells you anything about the plaintext, but when you have both of them you can recover the plaintext. (This can be extended to N > 2 as well)
Another way to think of it: For a given ciphertext, there exists a keystream corresponding to EVERY POSSIBLE plaintext of that length. If you don't have the keystream, you have no knowledge about which plaintext was actually used.
A stream cipher does not have this property. For a given ciphertext, there are at most 2^(keysize) possible plaintexts that could have produced it. However that can still be a very large number, and you have the advantage that the key is much smaller than the plaintext (therefore easier to store and distribute).
Do you really want to store ALL frames indefinatly?
I assume you are monitoring something (1000 cameras sounds like a whole city...) and you probably only want to keep the interresting stuff.
The way I read it, he won't know what's "interesting" until well after the events have been recorded. For example, assume that someone receives another anthrax letter, and assume that by then the post office is able to back-trace it to the original mailbox where it was deposited.
You'd pull the tapes of that location for the 24 hours between mail collections, and re-play them. Every person who dropped off an item would then be followed "back in time". Assuming a dense enough coverage of cameras (so that when they go out of frame on camera#320, they come into view on camera#319), you'd be able to follow everyone back to when they came out of their house that morning.
Then you just go to the court, get your wiretap orders and search warrants, talk to all their neighbors and offer cash rewards for incriminating information, etc. Soon someone will be rotting in jail (assuming there's room left after they've finished rounding up all the Linux programmers under the 2003 MPAA/RIAA Proud Bald Eagle Patriot Act). Voila, Freedom has been successfully defended once again!
A Quote about the Intel Server Motherboards (from post by a RealWeasel Designer)
"The bottom line with the console redirection, is that it's really BIOS redirection. It's only possible to see what's going on until the OS takes over from the BIOS"
Well, that's not really a problem because it's only the early boot stuff (BIOS, SCSI card setup, etc) that needs hardware support. Once your bootloader activates, it can just talk directly to the serial port without needing the "redirection" layer.
OpenBSD is particularly good at this. If you take a standard installation boot-floppy and create one file "/etc/boot.conf" with the line "set tty com0", it's possible to do a complete network-install of the OS onto a new server without ever attaching a keyboard or monitor.
It's nice to have some type 8e around too - Linux LVM. Logical volume management lets you do some cool things, like re-sizing your partitions with the data in place. You can add free space to a logical volume with reiserfs while it's "live", although you have to unmount the volume if you want to shrink it. *Very* handy when you don't know at install-time exactly how much space is going to be taken up by your/home,/usr,/var/log, etc.
Of course the Amiga "RDB" partitioning scheme had its nice points too. Linux can read it, but I don't know if there are any Linux tools to create one.
Yeah, repost!:) I only managed to catch it in "older stuff"
< AOL/>
For anyone who's interested, the Canadian government is currently considering changes to our copyright law (DMCA-style). However they at least had the decency to ask for public comments. The deadline for sending in comments was Oct 22, but it's still worth reading some of the material here and here
Intel ISP1100 - a nice 1U chassis+motherboard, designed to run headless (with serial-console support). I don't remember exactly how much you can control over the serial port (e.g. I don't remember if you can power it on/off or reset it, like you can on some of the HP kit), but it does give you access to the BIOS.
Note that it's a bit noisy, so if it's going to be a "home server" you probably want to put it in the basement.
Or you could just slap a "PC Weasel" card into a regular server, and get console redirection over RS-232. [Note: despite the name, this is a real company and product AFAIK. No relation to www.realhamster.com.]
There's TCFS too (Transparent Cryptographic File System). It doesn't need to use a loopback device, but on the other hand it doesn't hide all information (e.g. filenames aren't altered).
USA mirror of TCFS site is here, but looks a bit out of date.
Slashdot Mirror
Heinlein's "Let There Be Light" (in the same collection of stories copyright 1950, although it was probably written earlier) is about an inventor who develops materials that convert electricity to light, and light to electricity, at high efficiency. The materials are cheap enough that solar power becomes essentially a free source of energy (and the story deals with how the established power-generation industries react to his invention; hint: they're not pleased).
I'm not sure exactly when it was written relative to the actual development of photovoltaic cells (used to generate power, not just as light sensors or physics experiments), electroluminescent backlights, LEDs, etc but it would be interesting to look it up.
"The frame of reference in which the microwave background radiation of the universe is stationary" Hmmm, I'm not a physicist & it's quite possible that this statement might mean somthing other then what one would logically assume it to buuuut - where might this be?
I think the original poster meant something like "the frame of reference in which the dipole anisotropy of the CMBR vanishes".
Right now, measurements of the microwave background radiation are blue-shifted in one direction and red-shifted in the opposite direction. If a spaceship left earth and accelerated toward the red-shift, it would eventually see the red- and blue-shifts disappear. You could then say that the spacecraft was "at rest" in the universe. However it gets more complicated when you have to consider the expansion of the universe - two distant observers can each be locally "at rest" yet they will have a relative velocity.
(google on "COBE" for more information)
I also don't think that coliders are run 24/7 as someone else suggested / wrote.
Tell that to the grad students who are there at 2AM running experiments. I had a summer job at TRIUMF in Vancouver, and I can assure you that they don't just unplug the cyclotron at 5PM and go home.
I had to run a few shifts on one experiment that was shooting muons into cryogenic solids. Typical sequence:
- Collect data for 30 minutes
- Adjust temperature setpoint on the controller
- Go down to the experimental floor (involving various safety interlocks to ensure that the beamline is shut off before you open the door).
- Turn a liquid-helium valve just a little bit (this was the coarse temperature adjustment; the electric heater was the fine adjustment).
- Go back up to the data-collection room and press "start" (assuming you turned the valve by the right amount; if not go down and try again)
- Repeat until the sun comes up and they let you go home.
Particle physicists tend to be very good at Solitaire and Minesweeper.
this may actually be a cure. A CURE for cancer
Good. Now, the next time some "basic research" project like the SSC or a NASA planetary probe gets government funding, people won't be able to ask why their tax dollars are being "wasted on this %^#@$ instead of trying to find a cure for cancer" (and advances in genetically-modified foods should be able to get rid of the "... ending world hunger" one before too long too).
[Yeah I know, but my Karma's at 50 anyway, so go ahead and take your best shot...]
[Also, I remember reading about monoclonal antibodies in Discover or a similar publication back in the '80s. It doesn't appear to have been the miracle cure they thought it would be. Hope they have better luck making the jump from mouse to human this time]
so I poked around the chart of the nuclides to see how one would make Ac-225[...]But Ac-225 doesn't seem to have any such nice precursor decay paths with short half-lives.
I did a bit of web searching (with my CRC "Table of the Isotopes" handy), and it looks like the key is Uranium-233.
U-233 can be formed in a breeder reactor from Th-232, by: Th-232 + n -> Th-233 -> Pa-233 + e- -> U-233 + e-
Once you have the U-233, U-233 -> Th-229 + alpha -> Ra-225 + alpha -> Ac-225 + e-
This page at ORNL indicates they have a stockpile of 400kg of Uranium-233, and are "the only significant source of bismuth-213 [3 decays down from Ac-225, also useful for cancer treatment] in the western hemisphere".
I learned the correct pronunciation several years ago. I don't think they ever destroyed any of our packages, but there was one that came from the US up to Canada, got as far as our building (but not our office), circled around a bit, and ended up back in the US. We later found out they had tried to deliver it to another company down the hall, who had naturally refused to accept the shipment.
On the other hand, Oops did have a nice web tracking system so I could follow the adventures of this poor little package (which was a component we needed semi-urgently for a demo system). So they're not all bad.
p.s. Don't let them do the customs paperwork when you're bringing a package into Canada (slow and expensive, in my experience). Get your own customs broker.
This site has some good "Joe Sixpack" antigravity (specifically, a live frog being levitated inside a solenoid). Nothing to do with neutrinos, though.
Am I the only person on the planet who thinks that it's a bad idea to be sending so much coded E-M and junk hardware outsystem in order to make contact with aliens?
Greg Bear's The Forge of God and Anvil of Stars discuss this idea. Ships are designed for stealth, and Bad Things happen to a certain planet whose inhabitants weren't careful to shield their radio transmissions.
Plenty of today's PCMCIA NICs don't have dongles, e.g. Netgear FA411 (not an endorsement, just a remark).
Given that the thickness of a PCMCIA card is smaller than an RJ-45 plug, any PCMCIA NIC is going to need some kind of a kludge. The options I've seen are:
- Dongle
- "Pop-out" connector; cable plugs in vertically
- Double-height card (e.g. Xircom RBE-100)
Dongles suck, those little pop-out connectors just seem flimsy (and I have seen a couple of broken ones), and the double-height card is no good if your laptop only has 1 PCMCIA slot or you want to have 2 cards. It's much nicer just to have a real Ethernet port on the side of the laptop.
Another advantage of built-in Ethernet can be performance. Maybe this isn't an issue any more, but I seem to remember that in the early days a PCMCIA "100baseT" NIC couldn't get near 100 Mbits/second due to the limited bandwidth of the PCMCIA interface.
The problem I have noticed with the psyc's of physics teachers is they try to simplify the data to the students in an attempt to be hip... my high school professor called g 9.8m/s^2 where as my party school ECU professor in phys1000 called g 10m/s^2... this kind of thing bugs me a little.
10 m/s^2 is close enough for rough calculations. Often it's more important to illustrate some general principle, rather than to come up with an "exact" number. Even 9.8 is an approximation (the 1986 CODATA recommended value is 9.80665), and 'g' isn't even a constant - it depends where you are on the earth (and on other factors).
I looked up neutrino last night online and the def was short: a particle that has no mass and who's charge is neutral.
Find a better reference. There's some material here that looks like it might be decent. I've seen better pages, but I don't have the bookmarks handy.
...have no charge and no mass...
No charge - correct. However, as the article mentions, recent experiments indicate that neutrinos have some mass. They also have spin 1/2, like electrons.
are very fast
This is related to mass. If they had zero mass, they would travel at the speed of light (like photons, which have no rest mass). However, if they do have mass, then they have to travel at slightly less than the speed of light.
Supernova observations can be used to estimate neutrino mass, by measuring the time difference between the arrival of visible light from the supernova, and the arrival of a neutrino pulse. Over those vast distances, even a very small difference in speed could lead to a significant difference in arrival times.
and pass through the planet so fast most detection has to be done underground...
This is a bit off. The interesting item is that most neutrinos pass right through the planet without interacting with any atoms. Because they interact so weakly with matter, a detector will only see a very small number of events caused by neutrinos, even though there are bazillions of neutrinos passing through it every second.
However, a detector on the surface of the earth would also see events not from neutrinos, but from other cosmic radiation like muons (actually, muons generated in the upper atmosphere by cosmic radiation). Going deep underground blocks out all particles except neutrinos, enabling the experimenters to get accurate measurements.
It is actually quite normal for planes to crash every now and then, therefore it is most likely to be an accident.
A good example to support this point is the Sibir Airlines plane that went down in the Black Sea a month ago. Initially it was assumed to be terrorism (especially since the plane departed from Israel). However the consensus is now that it was hit by a stray Ukrainian missile that got away from its test range.
So even though terrorism might be the most likely reason for the New York crash, and the first thing that should be investigated, it is not the only possibility.
That's why I think it's very unfair to call Alan's behavior "self-censorship".
I agree - it's more of a "work to rule" protest.
or some reason I was thinking about those who were tried & convicted. I believe that if it has been proven that you are indeed guilty of committing a crime, you have no rights.
That's a load of crap, for two reasons.
1) Wrongful convictions. If you look here you will see several cases of people jailed for murder, and released years later when they were found to have been innocent of that crime (thanks to advances like DNA testing). These are Canadian cases, but I'm sure there are American examples as well; hopefully they all lived long enough to take advantage of their overturned conviction.
2) Bad or arbitrary laws. People can be locked up in one area for behaviour that is perfectly acceptable in another area (e.g. drug and alcohol laws in Netherlands vs. USA vs. Saudi Arabia, the Dmitry/DMCA thing, or those quaint areas where certain sexual acts between consenting adults are illegal).
In both cases, I believe the person involved does NOT automatically lose all of his rights once he's convicted. The person in the first case has a right to say "I didn't commit this crime", and the person in the second case has a right to say "What I did shouldn't be a crime". Take those rights away, and you're heading down a *very* slippery slope. [rather than invoke Godwin's law, I'll stop here]
My personal paranoia and suspicions aside, who would sell their HD to a stranger *without* first wiping the disk?
Well, a local dot-com went out of business recently, and auctioned off almost all of their corporate and development servers (including the Visual SourceSafe repository) without wiping the drives. I've also bought an un-wiped computer from a consignment shop. So I wouldn't automatically assume that the laptop in question was stolen.
I wonder if some similar technique could be used to produce thermoneuclear fusion.
See, for example, this Scientific American article about "Z-pinch fusion".
Would an attack to MD5 all known IP addresses be trivial, or extremely difficult?
There are at most 2^32 possible IPv4 addresses (fewer once all the "special" ranges like 127/8 and multicast are taken out). MD5 produces a 128-bit (16-byte) hash, and an IP address can be stored in 4 bytes.
You could construct a lookup table with 20 columns (16 bytes for the hash, and 4 for the IP address that produced it) and 2^32 rows. That's about 85GB - a consumer-level hard drive, these days.
Generating the table wouldn't take much time (I'd guess a few hours) and would only need to be done once. So I'd rate this as an "easy" dictionary attack.
Now if a random salt value was hashed along with each possible IP address, you'd have to re-generate the entire 85GB table for each salt value. So this would make the attack more difficult, but it would still be possible to recover several IP addresses per day on a regular PC.
A black hole without the "doughnut" of hot matter is not in conflict with current theory, if it is massive enough.
But according to the article, this black hole *does* have the hot accretion disk (as well as a huge jet blasting out of it). The missing "doughnut" is cooler matter (emitting in infrared, not X-rays) that they expected to find around the disk.
I think (but I'm too lazy to check) that there's a picture in the Kip Thorne book you mentioned showing a few possible theories for what the gas around a black hole could look like, with a variety of electric and magnetic field patterns. So this "no doughnut" observation will probably help to refine those calculations, but I don't see it overturning any fundamental black-hole concepts.
if it's a truely random key (hard to find) then there are no patterns to take advantage of. it's unbeatable.
If it's not a truely random key, it's not a one-time pad (in the standard sense) but rather some type of stream cipher.
A stream cipher uses a keyed mathematical algorithm to generate a stream of data that "looks random" but of course is completely deterministic. This keystream is then XOR-ed with the plaintext, as in the OTP.
I find it helps to think of the one-time pad as "secret splitting" - you take the original plaintext, and divide it into two halves (the random keystream, and the keystream XOR the plaintext). Neither half by itself tells you anything about the plaintext, but when you have both of them you can recover the plaintext. (This can be extended to N > 2 as well)
Another way to think of it: For a given ciphertext, there exists a keystream corresponding to EVERY POSSIBLE plaintext of that length. If you don't have the keystream, you have no knowledge about which plaintext was actually used.
A stream cipher does not have this property. For a given ciphertext, there are at most 2^(keysize) possible plaintexts that could have produced it. However that can still be a very large number, and you have the advantage that the key is much smaller than the plaintext (therefore easier to store and distribute).
Do you really want to store ALL frames indefinatly?
I assume you are monitoring something (1000 cameras sounds like a whole city...) and you probably only want to keep the interresting stuff.
The way I read it, he won't know what's "interesting" until well after the events have been recorded. For example, assume that someone receives another anthrax letter, and assume that by then the post office is able to back-trace it to the original mailbox where it was deposited.
You'd pull the tapes of that location for the 24 hours between mail collections, and re-play them. Every person who dropped off an item would then be followed "back in time". Assuming a dense enough coverage of cameras (so that when they go out of frame on camera#320, they come into view on camera#319), you'd be able to follow everyone back to when they came out of their house that morning.
Then you just go to the court, get your wiretap orders and search warrants, talk to all their neighbors and offer cash rewards for incriminating information, etc. Soon someone will be rotting in jail (assuming there's room left after they've finished rounding up all the Linux programmers under the 2003 MPAA/RIAA Proud Bald Eagle Patriot Act). Voila, Freedom has been successfully defended once again!
Be seeing you...
A Quote about the Intel Server Motherboards (from post by a RealWeasel Designer)
"The bottom line with the console redirection, is that it's really BIOS redirection. It's only possible to see what's going on until the OS takes over from the BIOS"
Well, that's not really a problem because it's only the early boot stuff (BIOS, SCSI card setup, etc) that needs hardware support. Once your bootloader activates, it can just talk directly to the serial port without needing the "redirection" layer.
OpenBSD is particularly good at this. If you take a standard installation boot-floppy and create one file "/etc/boot.conf" with the line "set tty com0", it's possible to do a complete network-install of the OS onto a new server without ever attaching a keyboard or monitor.
It's nice to have some type 8e around too - Linux LVM. Logical volume management lets you do some cool things, like re-sizing your partitions with the data in place. You can add free space to a logical volume with reiserfs while it's "live", although you have to unmount the volume if you want to shrink it. *Very* handy when you don't know at install-time exactly how much space is going to be taken up by your /home, /usr, /var/log, etc.
Of course the Amiga "RDB" partitioning scheme had its nice points too. Linux can read it, but I don't know if there are any Linux tools to create one.
Yeah, repost! :) I only managed to catch it in "older stuff"
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For anyone who's interested, the Canadian government is currently considering changes to our copyright law (DMCA-style). However they at least had the decency to ask for public comments. The deadline for sending in comments was Oct 22, but it's still worth reading some of the material here and here
Intel ISP1100 - a nice 1U chassis+motherboard, designed to run headless (with serial-console support). I don't remember exactly how much you can control over the serial port (e.g. I don't remember if you can power it on/off or reset it, like you can on some of the HP kit), but it does give you access to the BIOS.
Note that it's a bit noisy, so if it's going to be a "home server" you probably want to put it in the basement.
Or you could just slap a "PC Weasel" card into a regular server, and get console redirection over RS-232. [Note: despite the name, this is a real company and product AFAIK. No relation to www.realhamster.com.]
There's TCFS too (Transparent Cryptographic File System). It doesn't need to use a loopback device, but on the other hand it doesn't hide all information (e.g. filenames aren't altered).
USA mirror of TCFS site is here, but looks a bit out of date.