Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×

Comment Re:Public-key cryptography is the death of freedom (Score 2) 55

I don't like locked-down computers any more than you do. I hate ransomware even more; it's the single most despicable use of public key cryptography there is. But consider that without public key cryptography Apple wouldn't even be in a position to stop the FBI from hacking the iPhone. Individuals wouldn't even have the option to secure their personal communications, at least not in practice. (Yes, I know all about one-time pads. That's why I said "in practice"). Nor would we have the Internet, or at least anything like the one we have now. And without the Internet, computers of all kinds (secure or non-secure boot) wouldn't be nearly as capable and available as they are now because the volume and demand would be vastly less.

Comment Can't think of more deserving recipients (Score 3, Interesting) 55

I really can't think of more deserving recipients. I've never met Hellman, but I've met Diffie a few times, including when we testified to the Senate Commerce Committee during the 1990s Crypto Wars. He's a national asset whenever the NSA and FBI get a little too far out of line. Which is most of the time.

Comment CO2-sugar (Score 2) 158

Well, I've recently developed a machine to convert atmospheric CO2 into various simple organic molecules known as "sugars", which have the significant advantage over methanol of being relatively nontoxic. My design has been successfully tested for some time and it only requires sunlight, water and a few miscellaneous other inexpensive materials. And best of all, my machine is self-replicating!

Comment Talk to an old Telco engineer (Score 2) 169

Telephone companies used to have this exact problem. (Maybe they still do). Central offices contain a "mainframe", essentially a huge patch panel that connects cable pairs coming in the building to the switches. Technicians activated a given local loop by running a cross-connect pair. When service was discontinued, they'd often just disconnect the pair but leave it in the mainframe to clog things up for the future. I suspect this problem is decreasing with the growth of remote switching. E.g., AT&T U-verse terminates the customer loop in a VRAD cabinet in the local neighborhood instead of carrying it all the way to the central office.

Comment Re:Unconstitutional (Score 2) 545

I think you're right. The SCOTUS in United States v. Lopez ( see https://en.wikipedia.org/wiki/... ) ruled that Congress cannot constitutionally regulate who can walk into a school zone carrying while a gun, because this is not interstate - commercial activity. It seems likely the same reasoning would apply to walking into or out of a school zone at all. But who's going to challenge the constitutionality of this kind of law?

Comment Frequency Hopping vs Direct Sequence (Score 4, Informative) 67

I don't mean to denigrate her contribution in any way, but Lamarr's frequency-hopping spread spectrum is not the one used in CDMA mobile phones. It is used in Bluetooth.

Lamarr invented "frequency hopping" while CDMA cellular and GPS use "direct sequence". Frequency hopping is just what it sounds like: a narrowband transmitter is continually retuned to a different radio channel. Unless the receiver tuning follows the same sequence at the proper times it cannot receive the transmission.

Direct sequence XORs a narrowband signal with a high speed pseudorandom "chip" sequence, and the receiver undoes this operation by XORing it again by the same sequence properly synchronized in time. It closely resembles a keystream-type encryption system, though the "keystream" is not necessarily secret. The main difference is that direct sequence is a wideband signal while, at any instant, a frequency hopped signal is still narrowband.

Each method has advantages. Frequency hopping can be especially resistant to strong narrowband jamming, so it's a favorite of military systems (Lamarr's intended use). Direct sequence is easier to use with coherent modulation so it tends to use transmitter power more efficiently, and it can often provide precise timing and positioning as a side benefit. Or, in the case of GPS, as its primary purpose.

While CDMA mobile phones were very important in the 1990s and 2000s, it is now being replaced with LTE (Long Term Evolution), which uses OFDM - Orthogonal Frequency Division Multiplexing. So do many other modern terrestrial digital communication systems including DSL, HD Radio, DVB-T (but not ATSC), WiFi and DRM (Digital Radio Mondiale).

Comment No more tourist attraction (Score 1) 336

My guess is that the Metropolitan Police is far from gone from the area; they simply got tired of being an overt tourist attraction. The Ecuadorian Embassy is right around the corner from Harrod's and also the hotel where we stayed as tourists last summer. I got the definite impression that the police on duty were photographed a lot...

Comment Re:Noocular (Score 1) 298

Yes. I think cooler heads will eventually prevail, and they'll reverse their knee-jerk decision to phase out nuclear. One only has to look at German CO2 emissions over the past few years to see why. Of course, until they do I'm sure the French and Czechs will be happy to sell Germany their surplus nuclear power.

Comment Nuclear power phobia (Score 1) 69

Speaking of the horrific consequences of nuclear weapons testing in the Pacific, a big one that's still with us today is the knee-jerk phobia of nuclear power, often by people who can't distinguish between the two. Along with wind and solar, nuclear power is one of our chief tools to mitigate global warming, which will in the long term prove to be far worse than weapons testing. It sure doesn't help that the US government lied through its teeth about atmospheric testing. I've been trying to find a copy of Joseph Rotblat's paper deducing that most of the yield of the Ivy Mike and Castle Bravo tests came from the fast fission of the U-238 tamper, revealing as a lie the government's claim that fusion bombs were inherently clean. Anybody know where I can find a copy?

Slashdot Top Deals

If A = B and B = C, then A = C, except where void or prohibited by law. -- Roy Santoro