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More On The SDMI Crack & Why Digital Sigs Are Not
The latest issue of Crypto-Gram has some good coverage of the new digital signatures law as well as more on the SDMI crack. The signatures law is interesting - essentially claiming that a digital signature law is /not/ the same as signatures.
Things like this go to show that you need humans to mediate human interactions. The semantics of signing that Bruce talks about are a human issue, and only a true AI might become acceptable as a suitable substitute for a human in many subjective (and legality, value, trust - all are subjective) issues.
The reason we trust the notary public to countersign a document is that we are willing to believe what a human has seen and done because we can relate to it. The way you can lie as a notary public is pretty well known to humans - but forgery of digital signatures or hijacking a legitimate one is pretty new area for humans.
Tamper-proof computers would be needed for any digital system to be truly trustworthy, but that is probably raising the bar too high - higher than we keep it for our usual activities. What is required are procedures and oversight that humans can feel comfortable allows such a statistically low chance of error - through malice or accident - as to be worth trusting.
It is only partially attacks by other humans, thus, which we fear in digital signatures and similar mechanisms (like electronic voting). It is also machine error. We wants humans to recount votes and attest to signatures. Until more people are comfortable with the machines this will continue.
Finally, I will tip my hat to the open source community: by opening up the black boxes, people will start to feel more comfortable with machines - even if they remain ignorant. Few people actually fix their own cars, but over time they became confident that the standards and knowledge were such that they could trust those who do, and that the information was available for them to at least perform some rudimentary oversight if needed (indeed, as more car parts become black boxes, people are LOSING their trust in cars...)
So, what we need is comfort levels for humans, through open systems, and acceptable standards and procedures which maintain the highest feasible levels of security, privacy, reliability, and trustworthiness in the subjective view of people... There are NO tamper-proof systems, electronic or physical, but we still have a society functions without total paralysis from fear of a total trust breakdown.
Digital signatures will come into their own with improved security and oversight (monitoring and reporting) on PCs...
o/~ we are pissed, we are pissed, we have to resist... o/~ - ec8or
Here's ; a link.
_____________
I don't want free as in beer. I just want free beer.
Bill - aka taniwha
--
Bill - aka taniwha
--
Leave others their otherness. -- Aratak
The point of this is that digital "signatures" are semantically nothing like what written siganures are and what they represent. A written signature is a verification that the person signing it has touched, and probably read, that paper. All a digital signature says is that someone's computer had touched the file or chunk of data in question. The distinction lies in the fact that while a person has to physically and intentfully sign something, there is no way to prove that some program, possibly malicious, digitally signed something for him or her, without their intent.
Because of this distinction, digital signatures lack the property that gives written signatures their validity. Aside from forgery, there is no possible way that a signature can be made without the person's will. It is that expression of will that matters, and cannot be assured in the context of an automated, albeit user controlled, process.
First. What legally speaking is a signature?
;-)
;-) (He writes great books though)
It's not as easy as it seems. Is it a cross on a piece of paper? It can be, particularly if the signer is unable to write.
Is it a thumb print. Yup could be.
Is it a digital signature. Yup often is.
The point is that the law is actually more flexible and subtle than its often assumed to be.
Ok. Can written signatures be forged? Of course. Happens every day and twice on sundays.
Can digital signatures be forged? Yes, either by cracking the cryptographic system (usually very hard) or by hacking into the system that has the cryptographic system running on it (usually pretty easy, although not always).
Also with digital signatures (and with written signatures) there is a question of identity - is the John Smith that's signing the SAME John Smith that's paying? And if so, who says so?
Either way a fraud can been commited. And either way the court is the place to duke it out.
Is a digital signature less secure than a written one? Right now I doubt it, although in future it may be less or more so depending on the systems used.
I personally think that Bruce Schneier is trying to drum up more business for his security company
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"The point is, like the keys you probably have in your pocket; the smaller computer probably isn't networked, and probably doesn't leave her physical possession. Therefore it is difficult to attack.
If it's networked, or gets stolen, all bets are off.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"The question is not the forgeability, but rather the fact that you actually do not create a digital signature. You do not perform the mod computation, you do not calculate the hash, you don't sign your software does it.
You have no way of knowing if "your" signature concerns X document and uses "your" key. You trust the software to open the correct document, (the os, the file system, and the encryption tool), you then trust it to find the correct key, you trust it to perform all calculations correctly, and then you trust it to copy the sig to the correct file etc. The point is you are not in control of this process, you have no way of ensuring the correct document and key is used, unless you have hooks in the OS and even that is questionable.
With pen signatures, any idiot can ensure he signed the correct document - with no assumptions. With digital sigs software that is too complex to fully comprehend is utilised.
Woe be on to them, all who rise against poor people, shall perish in a the end. Buju Banton
What does this mean? They can be "copied"? A digital signature, by definition, is attached to a single document. So "copying" it is meaningless/impossible. In contrast a physical signature can be copied and placed on a different document.
Well, I think the question is not: can a signature be copied? (Of course it can, otherwise you can't send it in email, silly.) It's: can a private key be stolen, thus enabling forged signatures? (Yes, it can, and probably more easily as the kiddies figure out that the value of a forged digital signature has gone up.)
[I]t's not clear if a digital sig would ever stand up in court, because you could always claim that your computer was compromised, which is not the kind of thing the court can rule on.
I don't think this is true. After the first few cases like this, our oh-so-techsavvy legislators will probably pass a Uniform Commercial Transactions in the Digital Millennium Signatures Act, which will say that all other laws notwithstanding digisigs are to be treated as binding, whether or not they are provably valid, at least on Joe User if not on corporations. (Let's hope not!)
sulli
RTFJ.
Sure it can. I stand next to the notary with my tamperproof palmtop. I hand him the document for perusal. He hands it back to me. I sign the document. The notary signs my signature and hands it back to me.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!""Common sense isn't." In headlines or in similar contexts, there is a rhetorical device (I forget what it's called) of leaving off the predicate noun of a "to be" verb. In general, the missing predicate noun can be replaced with "what {it is|they are} commonly thought to be." In this case, "digital signatures aren't" signatures.
Will I retire or break 10K?
Here is a point about digital signatures that I got from the first chapter that I found interesting:
What is to keep an somebody from signing something then later claiming that their key was compromised at that point and it wasn't actually them that signed the document?
"Friendly fire isn't"
I can't tell you who said it....but there you go.
Averye0
--o You're just jealous cause the voices talk to me and not to you! o--
That's not the point. The point is, whether you read it or not, we know you intended to sign the video club contract. You had it in your hands and chose to sign it. We can't prove that you intended to sign a digitally-signed message.
But do you trust the program that computes your digital signature? I think this is one of the applications where having access to the source is vital. Maybe it would be even better if the algorithm were very easy to implement, so everyone could roll their own signing program and be absolutely certain that it was kosher?
[TMB]
As I understand contract law, whether you see the document is relatively unimportant. Someone could take pictures of you, get you to sign a release form that you think is just signing for a delivery or some other such ruse, and then sell the pics. The release form would still be legally binding, as you should have at least looked at the form you signed.
So it is here. If you haven't taken measures to ensure that the program you use to digitally sign documents is doing so everytime and only when you intend to sign a document, then hard cheese. Use of a DS program, in conjunction with the law, is tantamount to declaring "I agree to be held accountable to any document bearing my digital signature."
So, the authour is quite correct in saying that a DS does not always mean that you saw the document, but given what I've detailed here, does it matter?
-TBHiX
We very rarely attempt to validate the written signature on a document by examining the signature. The physical signature functions more as an assertion of intent, with the identity of the person making the signature defined and validated elsewhere. (Typically defined somewhere else in the document and validated by the use of semi-public info such as SSN, or by accepting the implicit assertion that the person handing in John Doe's form is in fact John Doe.) Digital signatures, conversely, are intended mainly as a mechanism for identity validation. The assertion of intent is usually elsewhere (typically, a confirmation screen). They are different tools used for different purposes.
...that there may well have been a virus on the computer which stole the private key, passphrase, etc. This is like signing a document without realizing the evil banker has carbon paper and another document beneath the one you are signing.
He's not talking about how reliable PGP is, or the mathematics of public key crypto.
--
Infuriate left and right
I've heard this so many times, and it's just an assertion. Before public key crypto was out, they said the same. I believe you can't secure digital data against an insecure recipient who can decode it; nothing says the data itself can't contain stuff the user can't notice -- you can't do a mathematical proof about content / the human ear, people! What's to say they can't do inaudible phase shifts, volume changes you can't hear, and other such? I don't think they can, but it takes a lot of chutzpah to just say you CAN'T outright with no backing. They did a good (not good enough, it seems) job; what's to say they can't do sufficiently better? I'll wager it takes more than just more money, but I don't see why they can't. Any thoughts?
For large documents, obviously, you're not performing a signature operation on all the text. But, maybe at the bottom of the page, you put your unique public key ID (which is then used to find your public key in a big database), then another line with, say, date, cost, and PO #, then the calculated result. If you lose your little card, you simply go down to the post office (or somesuch), get a new one, and they invalidate the old one for any new use after date X.
Obviously, the big problem here is the public key database, but that's been the bugaboo all along. But the advantages of something like this are:
Disadvantages:
You could (and, I'd argue, should, with proper back-end privacy features) put proximity technology into this and use it as your gas speedpass, grocery-store bonus card, office key, and gym pass. I like the ideas of the prox-cards (with authentication) for checkouts (like the Mobil Speedpass) but am loathe to put a dozen dongles on my already too-heavy keychain.
Anyway, does anyone like this idea? Can anyone point me to a better way to do secure authentication/validation on paper or over the phone? (yes, I'm ignoring for the moment the possiblity of loss/theft of the card and/or PIN).
david.
my opinion on written signatures vs digital signatures is that, in the end, they both rely on a bsic concept: trust in the sytem.
Yeah, and Shneier is talking about how the "system" works: with a physical signature, you're trusting that someone hasn't forged/copied it, which is something you can at least try to verify in a courtroom (and having it notarized is even more useful in that way). With a digital sig, you're trusting that no one has compromised the signing computer, which is going to be totally impossible to verify in the courtroom. This is a key difference in the two "systems", as Shneier explains.
Digital signatures trust that the computer is reliable, and that no one else has access to the signature. Digital signatures can be copied.
What does this mean? They can be "copied"? A digital signature, by definition, is attached to a single document. So "copying" it is meaningless/impossible. In contrast a physical signature can be copied and placed on a different document.
But, so can written signatures. The articles states that a written signature guarantees contact between the signer and the document. What about forgery?
The article also mentions that public notaries are often used for important documents. Public notaries are people too; they can be bribed.
As Shneier talks about in Secrets & Lies, it's not about making a system which can't be tricked/hacked/broken/etc. It's about minimizing the risks of that, so that you can conduct communication and business meaningfully. Despite your claim that it's all a matter of trust in the "system", Shneier makes a very clear distinction between physical signatures, which, though they can be forged and copied, have a reasonable chance of standing up in court, especially if they've been notarized. Of course, you could trick this system, but it is difficult enough to do that that the system works most of the time. In contrast, it's not clear if a digital sig would ever stand up in court, because you could always claim that your computer was compromised, which is not the kind of thing the court can rule on.
And then there is a meaningless rant about how everything can be broken, making incorrect assumptions about Quantum Computing (which would only render Public Key algorithms unusable -- it would just require longer keys for Symmetric algorithms).
And then...
As of yet, only one encryption method has been proven to work flawlessly, and it's not even encryption: it was the translation of English into Navajo during World War II.
One-time pads are provably unbreakable. They're just not very useful, because of the difficulty of distributing pads.
Jeesh...
-Dan
I have written a truly remarkable operating system which this sig is too small to contain.
Someone could take pictures of you, get you to sign a release form that you think is just signing for a delivery or some other such ruse, and then sell the pics. The release form would still be legally binding, as you should have at least looked at the form you signed.
Wrong.
The document would not be legally binding because it was retrieved through illegal means. You may want to read up on the laws about fraud at some point.
(On the other hand, that *is* your signature on the document, so you *must* have signed it five months ago - still illegal, just hard to prove.)
Is this post not nifty? Sluggy Freelance. Worshi
>2. The computer is not a trusted environment.
;-)
>Well, if you dont trust your machine, then thats
>your own problem. I trust mine, because I take
>care of it remaining trusted.
Wrong. Wrong. WRONG!
Your win 98 machine is on a network. Then your machine isn't trustable. Full stop. If you think otherwise post your ip address and I'm sure someone will show you the error of your ways...
Even if that wasn't the case, there's nothing to stop someone breaking into you apartment/house and circumventing any security you might have. Physical access to a machine pretty much breaks all and any computer security. Unless you live in Fort Knox and even then you have to worry about someone bribing the guards.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Ah, but if it's tamper-proof, then how can anyone verify that it really works as intended and hasn't been compromised? Sounds like a leap of faith to me.
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As copyright owner of this comment, I authorize everyone to defeat any technological measure which limits access to it.
I suppose it's obvious by now, but this topic is about Bruce Schneier's CRYPTO-GRAM.
All that crap remind me of this radio shop where I used to live. They would do this promo to see if anyone in the community could crack the 'newest' best car alarm/shutdown device on their lamborghini. On the first day of the contest, someone always did it, usually spending less than $50 on parts. All of this just points to the fact that digital copyright protection is simply a deterrent.
The sad thing is that he had to stare at that picture for several hours, I mean really scrutinize it, in order to put it in ASCII.
-atrowe: Card-carrying Mensa member. I have no toleranse for stupidity.
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You are a fucking moron.
the SDMI contest has no real meaning
Actually the contest has a lot of meaning. Having the contest means that they can claim the SMDI technologies are "un-hackable." It means they can claim that the "S" in SDMI stands for "secure" rather than "stupid" or (insert your favorite swear word that starts with an S here).
It means that we will see SDMI devices in the stores sometime soon. It means "fair use" will no longer apply.
Be careful who you trust. No matter how careful I am about installing software, scanning for viruses, etc, I wouldn't trust any PC fully. Can you be _sure_ that Win98 has no backdoors? Can you be _sure_ that Linux has no backdoors?
The real danger in digi signatures is considering them to have the potential to be any different from regular signatures. If you require a notary to witness a physical signature, then you damn well better require a notary to _physically_ witness the real person issuing a digital signature. Maybe there's a digital means for authenticating a person better than a human notary, so that may be an option. But authenticating the person in a truly secure way is necessary. This is not only an issue for the signer, but also for the party with whom he is contracting -- if there is any doubt that the signature was inauthentic, they are open to litigation... so really, everyone wants authentication from human->document.
Of course, I am of the opinion that physical artifacts should not be done away with. For many tasks, they may be the best solution available -- if security is really at stake, you may be better off _not_ moving at full internet speed.
This is pure semantics. Of course signatures aren't unequivocal, absolute proof of anything, especially most digital signatures. There is no such thing as 100% proof. It's just a matter of how difficult it is to copy. A written signature is digital in a sense - an arrangement of particles that could be duplicated with the right technology. Can anyone say "replicator?" Any signature is merely evidence, not proof.
What is to keep an somebody from signing something then later claiming that their key was compromised at that point and it wasn't actually them that signed the document?
Its the same with crimes. If you commit a crime, the evidence isn't going to be absolute. I could use this as a defence - "Yes, I did happen to be in the same room as the murder victim while holding a knife, but thats because I was I was chopping veg at the time. Yes, I always chop veg in the bedroom. Oh, the blood stain on it was when the victim cut him/herself the previous week......". Now, I could be telling the truth, but regardless of the concept of guilty until proven innocent, in this situation I would probably have to prove my innocence. Only a fool would believe my story.
Security being compromised would be a more believable plea, but this would probably be in a civil suit, where they would use a balance of probabilities. You would have to show how your computer could have been compromised. They would have to show that you did mean to sign it.
A bunch of programmers read about digital signatures and they think "Great, here's a way to verify that a specific person signed a specific document. How cool." (And it is very cool, don't get me wrong). Then Shneier comes along and points out the problems with using these digital signatures to replace the role of physical signatures in our current legal system (they won't stand up to court challenge, because it's so easy to claim that the computer was compromised or the key stolen).
He's right. His point is about the legal system, not about the philosophical issue about how to verify that someone actually signed something. Sure physical signatures don't do that, but that doesn't matter. They work well in our legal system. He argues that digital sigs won't.
So everyone should stop making such a todo about how he's being solipsistic, or techophobic or whatever. He's talking about legal issues.
-Dan
I have written a truly remarkable operating system which this sig is too small to contain.
That's what keystroke loggers are for.
DNA just wants to be free...
How about some pointless speculation?
You're right that you can't make a mathematical proof, but you can make some reasonable/logical guesses...
Take bunch of digital data that represents a audio file. call it <A>.
Add a watermark to it, inaudible, but still detectable (we don't care how it's encoded, but in essence the data should be visible in the digital range. It'd be nice if speakers could not play it, but it's irrelevent.)
So now we have file <A+B>.
Let's now do something clever. We apply the latest, best, and tightest audio compression. Choose whatever you want, mp3, ogg, wma, etc.
We know that these algorithms work by throwing away data that cannot be heard. Frequency masking, volumetric masking, time phased masking, etc.
So we have that <B> is inaudible, already. Regardless of whether the <B> component is output by the speakers... MP3(<A+B>) => MP3(A)
So now we have a file that is, arguably, indistinguishable, from the original file <A>, and now no longer has watermark <B>
The conclusion? Watermarks can be removed without destroying the audible data. That's just how MP3 and such work. If one cannot remove watermarks, then the MP3 encoder must think the watermark is, well, audible!
We can always try to invert this 'proof',
The nick is a joke! Really!
GPL Deconstructed
Tamperproof because it never leaves my possession and because it is designed to be secure. It may or may not be networked- not all protocols require this.
What's to stop me having multiple signatures in normal life anyway? I don't think that this is a problem- its probably an advantage.
Standard contracts aren't distributable across a network reliably; they can be modified. Standard contracts most definitely ARE prone to deletion; crytographic protocols ensure that crypto-signed contracts AREN'T changed at all after signing otherwise the signature won't verify.
I'm not saying that crypto-systems are super secure. What I am saying is that they are about the same, and if used with care, can be MORE secure than the other methods used. They are NOT magic-solve-all-your-security issue schemes. But they are useful tools.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"-jon
As the article points out, the SDMI contest has no real meaning, other than fame and dough for them. Nothing that can be decrypted can't be cracked. It may be hard, but there is always a way. I especially liked the little point that watermarked files can still be duplicated. It's just like the ID3 tag "copyrighted". A pirate is not very likely to care about the FBI warning on the first part of a copied video tape. Of course, this still doesnt protect the average consumer with the intelligence of a potato, who believes what the company tells them, and goes out to buy all the software for this "copy proof signature". Technology: friend or foe?
I am !amused.
After reading this article I have a few concerns about what this person is talking about:
1. He mentions that a digisig is less secure than a normal sig because the person does not have to read what he/she is signing. Well, isnt this also the case with normal sigs? How many of you read the contract when you joined your local video club? It is hoped that the person doing the digisiging will have read and agreed the document. Something that could be done about this could be maybe include a signing message, in which you sign the document, and also include a short sentence like "I agree" or "I disagree".
2. The computer is not a trusted environment. Well, if you dont trust your machine, then thats your own problem. I trust mine, because I take care of it remaining trusted. Sure, some assumptions have to be made, but one thing is caution, and another paranoia. I am SURE that at this moment I have no backdoor programs running in my Win98 system. I also know that I have no Office virii in here either. This is not only due to the antivirus software, but also to my downloading/trusting habits. I also have to make the assumption that Win98 itself is not sending data to someone else, but then that becomes the stuff of legend amongst the MS haters.
Point is that forgery and thievery occurs in the real world and in the digital world. The idea that a program will sign another document when you didnt tell it is akin to telling you to sign with a pen a peice of paper and having underneath it a carbon paper and another document with the signature line in the same place, but saying something else. Or hell, even easier, just beating you until you sign a paper or you die.
This sort of fear towards technology is nothing new, but it is shocking to see who is displaying this fear in this case.
The problems presented in this article are not computer problems, but rather human problems, and the lack of ethics in the world of today (and yesterday too).
The only thing that you CAN trust is the key (and only to the extent that that particular public key encryption method is secure. RSA, for example, is only as secure as the product of two primes is against being reduced.)
So, how to make digital signatures more "secure" and more tracable? One solution, again, as the article noted, is to have the whole signing mechanism offline and on a PDA device.
However (once again, as the article noted), you can't necessarily trust the software or hardware to do what you expect.
The only way round this would be to have a PDA device with fixed software & hardware, which was mathematically proven "correct" and "trustable". Instead of having generic apps run on the device, the device would ONLY read/write documents, never code.
This would require a near-universal format for documents (so that the PDA could allow the user to verify what it was they were signing). Pockets filled with 1001 cards for memberships, stores, cardkey locks, etc, are bad enough. Imagine having 1001 PDAs stuffed in there, as well!
A universal document format is unlikely to happen in my lifetime, even if workable whole-body crypgenics did.
Having said that, let's play-pretend that Microsoft and SUN will some day learn to play fair with everyone else, and that someone is willing to go to the effort to develop a proven, tamper-proof PDA to the former A1 standard, with sufficient screening to block any remote scanning, such as TEMPEST, sufficient memory to hold entire documents in RAM, sufficient ease-of-use to be practical, and biometrics to validate the operator.
THEN, we can talk about digital signatures which can be sensibly matched to the signer.
There was a thread about this on the vuln-dev list as well:
hacksdmi?
It is the cost of entry to forgery that is the basis by which we can judge any signature method. Creating a well forged signature is difficult... you must know the person well, or have lots of practice forging their signature (or all handwriting). Bribing a notary republic is expensive, can can blow up in your face. And for all of these activities, they are not what most people consider 'fun and involving', or practicing the skills required a particularly safe thing to be caught doing. However, with digital signatures anyone who has access to a computer lab has access to the tools required. There is a large society of hackers who enjoy trying to take apart encryption methods, and exploits are often posted publicly up for all to see. Well known exploits have programs written specifically to take advantage of them, allowing barely skilled users to utilize the security flaws. Thus, the cost of entry for digital forgery is lower than the cost of entry for physical forgery. The chances of detection are lower, and the ability to hide your tracks is greater. This is why digital signatures must have a much GREATER security level than normal ones, and the differences inherent in how they are, and are not, secure from written signatures should be well documented and publicised. Raven
And my soul from out that shadow that lies floating on the floor
"I will trust Google to 'do no evil' until the founders no longer run it." Hello Alphabet.
I liked the comment on solipsism.
The only way to build more trust (not build trust, just more) into the system is if the digital signature captures the info of where it was created, when it was created, and what program it was created on. Timestamps and logs, essentially.
This just boils down into the whole trust issue, however. Someone somewhere must place trust into the system. For the signer, that the system works as it is proposed. For the unsigner, that the signer packaged and signed the parcel in good faith, and that no tampering was done. In the digital world, it's possible to forge and copy with much better fidelity than it is in the real world. In the real world, it takes masterful manipulation of real things.
In the digital world, it is only bits. Which can be hacked, copied, and played around with.
Which means that digital solutions have to be created to make hacking, copying, and forging that much harder. Not that it will be impossible, just that it will be more of a deterrent.
The nick is a joke! Really!
GPL Deconstructed
From dictionary.com, a definition of solipsism...
1.The theory that the self is the only thing that can be known and verified.
2.The theory or view that the self is the only reality.
As far as I understand it, this 3 dimensional world you speak of is a construct of the self called Cuthalion. Your statement then, that it is an excellent model for explaining everything, is the point of solipsism. That everything we know is just a model of reality, and that reality itself cannot be be known without our senses.
If I understand solipsism correctly, each person can only ascertain their own reality (by assuming that they trust their senses).
To share their reality with other people is another trust exchange. Once we have shared realities, we can construct another reality, a second level of reality, that we both believe because it fits with the first level personal model of reality.
Perhaps you can be more clear; what about solipsism don't you believe in?
The nick is a joke! Really!
GPL Deconstructed
my opinion on written signatures vs digital signatures is that, in the end, they both rely on a bsic concept: trust in the sytem.
... an excellent book, i might add)
Digital signatures trust that the computer is reliable, and that no one else has access to the signature. Digital signatures can be copied.
But, so can written signatures. The articles states that a written signature guarantees contact between the signer and the document. What about forgery?
The article also mentions that public notaries are often used for important documents. Public notaries are people too; they can be bribed.
There is no truly secure method of signing a document, of encrypting information, or anything else of the sort. Anything and everything can, and will, at some point be broken.
As it stands, PGP is fairly secure. Current computers can not current perform the mathematics required to break a PGP encryption in a reasonable amount of time. However, when quantum computers are available, PGP will be useless.
Although the advent of quantum computers will also bring about quantum cryptography, which has been labelled as "unbreakable."
True, the concepts regarding quantum physics would currently render the encryption unbreakable, who knows what technologies may later emerge?
As of yet, only one encryption method has been proven to work flawlessly, and it's not even encryption: it was the translation of English into Navajo during World War II.
(For more information on these subjects, read Singh's -The Code Book-
--------------
Well, not really, but this is the basic solopsistic problem.
/without/ using your senses?
/probability/ of error.
Since your only interaction with the world is through your senses, how can you verify that it is as it seems, or even exists at all;
The best answer that anyone ever came up with is "I refute it thus" and kicking a rock. (not making this up). In reality, there is no true answer, indiviudals must make the "leap of faith", or the "leap of presumption" at least, and presume that the world is more or less as it appears to be.
Since true signatures validity can only be 'proven' by either A) testimony to the fact (which doesn't really require the signature, after the testimony) or B) the voice of 'experts'; the 'experts' can be cryptography experts, and can, like the hyndwriting experts, testify about the
And it is ultimately only about how probable it is, since you can't prove anything.
-- Crutcher --
#include <disclaimer.h>
-- Crutcher --
#include <disclaimer.h>
The paper-digital signature analogy is very valid. And it is often ignored, often in the name of improving E-commerce, or more recently, with digital signatures being advocated as authentication for electronic voting. The important thing is that both are subject to tampering. Unlike with a signature on paper, which is very hard to duplicate exactly with another person using a pen, and where copies are obvious (i.e. a photocopy would have trouble passing), digital 'signatures' can be made exact without detectability provided that the manner in which your private key was stolen is no longer apparent. In addition, courts, judges, and police are unlikely to understand these issues.
These are important issues to consider. Perhaps one day we will be required to use digital 'signatures' on a regular basis to conduct normal everyday business -- perhaps the software used will be a propietary system provided by one company (let's call this company Macrosoft for purposes of illustration). Now if the single company Macrosoft provides the software, and due to trade secrets there's no proper external review of the software, and anti-hacking treaties make white hat review impossible, perhaps one day we will live in a world where those with the knowledge can commit easy forgeries and impersonate others, and the citizenry will be powerless to do anything.
Digital Signatures: Be careful what you ask for, as you may get it.
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