Talk:PURPLE
|
|
| Missing image Key-crypto-sideways.png WikiProject on Cryptography | This article is part of WikiProject Cryptography, an attempt to build a comprehensive and detailed guide to cryptography in the Wikipedia. If you would like to participate, you can choose to edit the article attached to this page, or visit the project page, where you can join the project and see a list of open tasks. |
|
Pending tasks for [[Template:Articlespace:PURPLE]]: (https://academickids.com:443/encyclopedia/index.php?title=Talk:PURPLE&action=purge) | edit (https://academickids.com:443/encyclopedia/index.php?title=Talk:PURPLE/to_do&action=edit) - watch (https://academickids.com:443/encyclopedia/index.php?title=Talk:PURPLE/to_do&action=watch) - purge (https://academickids.com:443/encyclopedia/index.php?title=Talk:PURPLE&action=purge) | |
|---|---|---|
- Note: comments on this page have sometimes been most recent at the top.
Ortolan88: Actually, the Purple machine (called Alpabetical Typewriter with a date indicator by the Japanese) was made of electrical stepping switches, not rotors. It doesn't appear to have been influenced much by the Enigma design, or indeed by any of the rotor machines. The Japanese Navy Captain who desinged them all followed his own star, though there is some mention of a Polish Army Captain who went to Japan to help in crypto design in the '20s. Perhaps an influence? Leo Rosen at SIS was asked to build an equivalent after the SIS team (under Frank Rowlett) figured Purple out, and in an ironic coincidence, chose exactly the same stepping switch the Japanese had used.
On another subject, there is an unsigned comment below talking about digital v analog. The following may help.
All of the rotor machines, and the Purple and its predecessors (Red and the M machine) are actually digital in the sense that a substitution (on either encryption or decryption) is digital. Either q is substituted for f or it isn't. Whether it should have been is another question having to do with how well an analog machine (rotors rotating, electrical contacts making or breaking properly) behaves digitally. Exactly similar considerations underly digital circuits in modern computing equipment. They are implemented using transistors of various types, all of which work by controlling the flow of electrons from hither to thither. A meaningful flow isn't any particular number of electrons for a digital 1 or exactly zero for a digital 0 -- if that happens to be the assignement at that particular logic gate just then. There are always guard bands. Thus, 'a 1 is any voltage greater than such and less than so', while 'a 0 is less than this and greater than zero'. The value of such is always greater than this by some amount, and if the voltage falls between such and this, there will be trouble. A good bit of digital electrical design is devoted to ensuring that ambiguity of this sort doesn't happen. Reshaping circuits, regenerating flipflops, Schmitt triggers, are some of the dodges used.
For a long time, T(ransistor)T(ransisitor)L(ogic) in which one value is nominally +5VDC and the other 0VDC was the standard. In recent years the larger of the two voltages has become smaller. +3.3VDC is used in the PCI bus and +5VDC was used in the first version of the PCI bus. This saves power, extends battery life, and is otherwise good. It also squeezes guard bands and makes tighter circuit design mandatory for digital cicuits, lest the ambiguity get to be too much.
Hope this helped some,
ww.
What do you mean, "analog computer"? Wouldn't it need to be digital? Remember, "digital" does not have to be computerized. A mechanical adding machine can be digital.
Well, the the purple machine is like the Enigma. It consists of a bunch of interlocked letter wheels. The interlocking relationship changes after each letter is typed. In effect, it is exactly the same technology as an odometer, which is certainly analog.
A digital computer works on numbers. An analog computer works on mechanical relationships. I would be interested in hearing of any mechanical adding machine that was digital. An analog computer, such as an odometer, is usally single purpose while a digital computer is multipurpose. Ortolan88
Sure thing -- I have used (obsolete) mechanical digital adding machines to add, subtract, multiply, and, with enormous effort, take square roots. The numbers were represented as digits using a series of wheels, one for each power of ten. Babbage's Analytical Engine was another example of a mechanical digital computer.
I'd also disagree with you about an odometer being analog. If the number is stored as a set of digits, then the representation of the number is digital, even if the representation of each digit is analog. Note also that the digits (except the lowest) move in discrete steps.
Here are four examples, showing the full gamut:
- Mechanical / digital: Babbage's Analytical Engine
- Mechanical / analog: Mechanical rotating-wheel integrators, slide rules
- Electronic / digital: nearly all modern computers, pocket calculators
- Electronic / analog: Op-amp based 1960s and 1970s analog computers
Note also that there is nothing requiring a digital computer to be programmable, or Turing-complete (even though nearly all are). For example, FPGA codebreaking engines and galactic physics simulators are special-purpose electronic digital computers.
Hello, The Anome,
Yes, but, and I am way out of my depth here, I am pretty sure that you're supposed to make a distinction between the representation of a value and the way that value is calculated and stored. You have to agree that a mercury thermometer is analog, but it represents values digitally.
As for the odometer, there's a little thing on the axle that transfers the rotary motion from the axle to the odometer, which replicates that motion on some other wheels that just happen to have numbers printed on them and an escapement mechanism (for those discrete steps). When you change your tire size, you have to change a little gear, else the odometer, and its companion analog computer, the speedometer, won't read right. To me that is the essence of "analog".
The odometer doesn't "store" anything. The original Mauchly-Eckert computer, a chunk of which is on display at Harvard U., used odometer mechanisms for display, but all they did was tell you how many times the relay they were attached to had fired, the data, I believe, was stored in memory.
(Fools rush in, I don't know Jack about this, other than having seen the display. My dad was a classmate of John Y. Atanasoff (who taught Mauchly and Eckert everything they knew), but I'm just a tech writer.)
A regular old-fashioned clock is analog too, by my definition, digital representation, discrete steps (some), and all.
That said, you probably know more about this than I do. There is no wikipedia article on computer history, but your outline above certainly belongs there. I think you'd have to have a pretty rigorous definition of the difference between analog and digital to do so, however. I have a little trouble with your roadmap because I think it is mixing the two. For instance, I think, and so does the wikipedia article on analog computers that the slide rule is analog.
What do you think of the wikipedia article on analog computers. It seems to agree with me. (I think it's fabulous!! Actually, it seems a little thin to me, but I couldn't fix it.)
There is no article on "digital computer"; that is redirected to Computer, which is longer, but pretty slapdash in organization. It says analog computers have "no discrete or digital computational ability". By the same token, the purple and Enigma machines didn't compute or store anything. To change the code, you moved the wheels.
Fun computer history fact:
- On warships there used to be an organization of humans called "the computer", often made up of members of the ship's band, who sat at a table in the depths of the ship during combat, performing simple math and passing along the results to the appropriate next person for the next calculation, which work in summary produced aiming trajectories and the like for the ship's gunners. The original log tables were computed the same way.
Best regards, Ortolan88
Shouldn't the title of this page be "Purple cipher"? Since it really was a cipher and not a code (even the article says this). - Crenner