Are you talking about the scheme in which I always use EFM, or the one where I use EFM1 on the first messages, EFM251 on the second, EFM89 on the third, EFM252 on the fourth, etc?
There's probably a pattern in those numbers somewhere.
"Neil Jones" wrote
Not in your terminology no - we agree a "method" or "algorithm" or "system". I'd call that a "key" as well, but you seem to reserve the term "key" to apply to an "algorithm+key" method.
"Neil Jones" wrote
So what does "obfuscation" use to convert the data? What is the difference between this "something" and a key? And what makes it "secret" - whether
*everyone* knows it, or just one-or-two know it (with others not knowing - eg with our enemy1 & enemy2), or that no-one but yourself & recipient knows it? If someone cracks it, and therefore now knows it, is it no longer encryption??You see, my contention is that "algorithm+key" is simply one sort of method, or system, to convert the data. Whether the system/method explicitly includes a certain "key" (as in EFM2 or EFM3 etc) or does not (as in EFM - using the "normal" table), I still call it encryption. Thus I class obfuscation as a form of encryption (although not as secure as encryption using a public key system, for instance).
You seem to artifically split off *part* of a system/method - calling it the "key" - and only class the system as encryption if the so-called "key" exists - and not only that, you need to specifically *call* it a key!
"Obviously"? Tell me you're being sarcastic.
Phew! You *were* being sarcastic.
It's not difficult at all.
1/1, 2/1, 1/2, 3/1, 2/2, 1/3, 4/1, 3/2, 2/3, 1/4, 5/1, 4/2, ...
AIUI this is not possible.
encryption
But looking at it from another point of view, you seem to artificially roll the key up with the algorithm and call it a system :-)
I'm obviously not explaining myself clearly - in which case I would refer you to an excellent text by Bruce Schneier -
This is what is meant when it is said of some people that they have a brain the size of a planet.
"Ronald Raygun" wrote
Not really, no. There are twice as many "thirds" numbers (eg 1/3, 2/3) which aren't whole numbers, as there are whole numbers. Because just after whole number 0, you have 1/3 & 2/3. Then just after whole number 1, you have 4/3 and 5/3. Then just after whole number 2, you have 7/3 and 8/3. You get the picture.
Thus, you can say that "obviously" there are *twice* as many "thirds" numbers between the whole numbers, than there are whole numbers themselves. There are an infinite number of both - but the number of "in-between thirds" is a bigger infinity than the number of whole numbers - twice as big infact.
The number of fractions is much bigger than the number of whole numbers (both infinite). There are even more irrational numbers.
"Ronald Raygun" wrote
"Ronald Raygun" wrote
Well done! Apparently, a lot of people baulk at having to put fractions into order like that.
"Ronald Raygun" wrote
Yep - there are just so many of them! Much like trying to list all the possible algorithms for converting (encrypting) data....
there are the same number of rationals as integers - the smallest of all infinities and usually given the first letter of the hebrew alphabet with a zero suffix (aleph-0)
I think this might be 2^(aleph-0) or perhaps this is just the real numbers - can't quite remember
"Neil Jones" wrote
What chapter is obfuscation in?
When I get home tonight I'll have a look
No. You can't compare infinities like that, *because* they're infinite.
It's meaningless to say that one infinte set has 27 more members than another infinite set, and by the same token you can't say that one has three times as many members as another. It doesn't make one in any sense "more infinite" than the other. The real question is "Can you count its members?". If the answer is yes in the same way as that in which you can count the whole numbers, then the set in question is "equally as infinite" as the whole numbers.
There are the same number of even whole numbers as odd whole numbers, right? Why? Because you can pair them up, i.e. devise a one-to-one mapping so that for every odd number n there exists an even number n+1, and for every even number m there exists an odd number m-1.
Now, the same way, you can have a one-to-one mapping between whole numbers and even numbers. For each even number n there is a whole number n/2 and for each whole number m (which may or may not be even) there exists an even number 2m.
Picture yourself managing a hotel with an infinite number of rooms, and they're all full (because you're hosting an intergalactic conference of financial experts, attended by one delegate from each of the universe's infinite number of planets).
A casual guest turns up unannounced, and although all the rooms are full, you can accommodate him. Just move the existing guest in room N into room N+1 for all N>=1, and put the new guest into room 1.
This repeats all through the night as more tourists dribble in. In the morning, an infinite stream of coaches draws up, and you think they've come to take the financial experts away. Hang on, the conference isn't over till tomorrow, what are the coaches doing here already?
Horror of horrors! It transpires the coaches are bringing the delegates for the annual philatelist's get-together, which starts today, but which you had mistakenly booked in for next week. Never mind, just move the existing guest in room N to room 2N, for all N>=1, and put the stamp collectors into the odd rooms.
The fincancial people check out, and the chairman of the board which owns the hotel comes round. You reckon it'll look bad if half the rooms are empty, so you invite the philatelists in room N (N is odd) to move into room (N+1)/2, but the one in room 1 can stay put.
The company actually owns more infinite hotels apart from yours, in fact it owns an infinite number of them. The chairman has a discreet word with you and tells you the company has fallen on hard times and must close down all the hotels except one - yours. Mind you, as it happens all the other hotels are full, and all their guests are being dumped on you. They arrive next week. Can you cope? Of course you can!
Hmmm. I wonder what's changed since Mondex and the other e-cash schemes. They were abandoned because
- nobody was willing to bank (no pun) on the continued security of the "unbreakable EEPROM storage"; if breached people could generate their own untraceable cash
- nobody was willing to bank on RSA remaining unbreakable
- the Govt didn't want untraceable money transfers because they make tax evasion (called "money laundering" nowadays) easier
Yes.
Product used to be called "Magniview" or something like that. A sort of cross between iron filings and fingerprint powder. Paint it on and you can see the data.
Without a hint of irony, snipped-for-privacy@isbd.co.uk astounded uk.finance on 21 Apr
2004 by announcing:
No, you can't stop there. It's encrypted not only in a particular language, and then - apparently - in vibrations.
"Ronald Raygun" wrote
You obviously haven't read the same mathematics book. AIUI, there are a number of different "infinities". :-) [This was a looong time ago - cannot remember title/author.]
[Altho' I think my example involving thirds & whole numbers was a particularly bad one, because they are probably the same "infinity". But the infinite number of *irrational* numbers is not the same as the infinite number of *fractions*.]
I think youll find it was because if your card went to the great bit bucket in the sky, so did your money :-) ..you dont normally find the money in your wallet vanished because of a software bug ! "sorry I cant buy a round i've got GPF 0x0000CD". I'm sure if people felt they could hack into the cards and generate their own money you'd inexplicably have found a rapid uptake of the scheme!
I doubt the great unwashed had even heard of that
Well, thats no problem with C&P, its a very different scheme to MOndex
"Rob" wrote
[Tee hee!]
Correct, but odd integers, all integers, and rationals are all in the same kind.
But as you say the irrationals are of another kind, though I'm not entirely sure I quite follow why. I guess there are just too many ways to be irrational for a rational person to think of. There's probably a sexist remark in there itching to get out.
I'm impressed you both cracked it so quickly, but *you* get a bonus point for expressing it more concisely than Tim. I shall have to make the next test more difficult.
I'u coduyqimp nbv wkdk mddfptw ex pd tnvxhsq, rle *cqk* qun n ocpjb qemzs xlc gdsjnfxfsy gz lzqu wkxzhzdom fmmz Sam. U mttep wwrv oc ooyc vcg txun gkcv hvmq tbgltvpat.
It was the issuers who were worried about it, not the users.
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