Slashdot Mirror
Safecracking for the Computer Scientist
secureman writes "It looks like Matt Blaze (the University of Pennsylvania CS
professor best known for finding security flaws in the NSA Clipper Chip
and in master keyed
locks) is still causing trouble in physical security circles. There's a draft paper (dated December '04) on his web site
entitled Safecracking for the
Computer Scientist, which is a pretty in-depth look at what
computer security can learn from safes (and vaults). The interesting
thing is that it describes in detail the different ways that safes are
cracked, probably revealing techniques that locksmiths would rather you
didn't know about (there's a lot of security-by-obscurity there). The
conclusion seems to be that while safes can fail, at least they do so
in better ways than computer systems do. Warning: it's a
2.5 meg pdf file with lots of pretty pictures."
The information for the way that locksmithing is done (including lock picking) is available in most libraries. Ditto for safe and vault construction methodologies for the past 120 years.
How about a safe holding up to the
wgetting it at 12 K/s
X(7): A program for managing terminal windows. See also screen(1).
While trying to retrieve the URL: http://www.crypto.com/papers/safelocks.pdf
The following error was encountered:
Unable to determine IP address from host name for www.crypto.com
The dnsserver returned:
No DNS records
That's helpful.
-- Note: If you don't agree with me, don't bother replying. I won't read it.
Cmon, you expected a 2.5 mb file to last...
Here's Google's HTML-ification of the pdf (sans said 'pretty pictures')
It's been up less than 5 minutes and it's already inaccessible. What's the record?
http://mirrordot.org/stories/a98b5b5fc2096a7b567c4 b2e77ca0f1f/safelocks.pdf
Did anyone else read the headline and think this was some horrible spoof on "Queer Eye for the Straight Guy"?
Google HTML cache of the PDF:
: www.crypto.com/papers/safelocks.pdf+safelocks+cryp to&hl=en
http://64.233.161.104/search?q=cache:uKCwKOYICgkJ
-JD
Mod parent down. :/
A slashdotter who didn't build his own computer is like a Jedi who didn't build his own lightsaber.
http://shell.athenet.net/~files/safelocks.pdf
Good use of MirrorDot for once. Took only seconds and I can read the PDF.
"There is more worth loving than we have strength to love." - Brian Jay Stanley
...actually, sites have been slashdotted in the "mysterious future" before actually making it to the front page...
Live today, because you never know what tomorrow brings
All safes open using a maintenance combination of 12345.
Warning: it's a 2.5 meg pdf file with lots of pretty pictures."
It was a 2.5 meg pdf file with lots of pretty pictures. (that I will not be able to look at for a few hours. Damn.)
...using keyword "safelocks".
i don't know, i thought it was pretty funny
Its all these damn trouble making hackers and lock-pickers figuring out how to do it! Damn commies.
This comment does not represent the views or opinions of the user.
"Error: Document contains no data"
Hmmm...looks like this safe has already been cracked.
This could take some time. Fetch me my download hat and a 6 pack...
I think his comparison is on to something here.
A good safe is designed in layers, so that to get in, you have to break through each layer. And the more layers, the more time it takes. Safe-makers know no safe is completely secure, and all safes are crackable.
Time is the enemy of anyone looking to commit theft/robbery, whether that person is working physically or digitally. So the longer it takes the more secure the system it is.
While we defeinitely know security by obfuscation is stupid in terms of computer security, safety by layers makes sense.
If there were several layers of encryption (asymmetrical and symmetrical), compromising the system takes more time, and if one layer fails, the game isn't over just yet.
Admittedly secure traffic would be much slower than unsecured traffic, the benefits of this kind of layered approach would be more than worth it for data that needs to be as secure is possible.
You can't defeat physics.
"Good use of MirrorDot for once. Took only seconds and I can read the PDF."
True, but on occasion the PDF will be corrupt. So it's not foolproof.
"Time is the enemy of anyone looking to commit theft/robbery, whether that person is working physically or digitally. "
Less so with digital, and it's easier for the thief to distance themselves from their crime.
like it says its a troll
i had matt blaze for an undergraduate computer science course in operating systems at upenn this past semester, and in addition to being extremely knowledgeable when it comes to security issues, his all-around computer science savvy is remarkable
You are completely alone in this. I think it was a cry for help, not a troll. Pity the guy whose having subconscious issues with their sexuality, and lets it out on a /. forum.
That sounds like the combination some idiot would have on his luggage.
Thinkin' Lincoln - a web comic of presidential proportions
nize.
i spose modding the parent to funny would be an unsafe request...
Serenity now, insanity later.
So much for storing my 3rd replacement Playstation 2 in my safe.
I use FireFox and my brouser window goes NUTS when I click on the link... I thought I didnt have to worry after I dumped IE
Mr Feynman used to be well known for this sort of things, repeatedly cracking the Los Alamos safes to try to demonstrate how lax security was...
http://m.earth.org.uk/
Safe makers know that safes only slow down would-be theifs, and that no safe is perfect. If computer systems are analogous to safes, does that imply that we will never produce a "perfectly secure" system?
To me, it seems that it is possible to create a perfectly secure system, since we are not bound by the same constraints as safesmiths, such as materials expenses and limited material strength.
The challenge for IT security is that computer science loves to use abstractions, encapsulation, APIs, libraries and what not that let the programmer ignore the details of the internal complexity of systems. The problem is that it leads one to assume that these systems behave in some idealized fashion (the logical, black-box model of the system). In reality, the systems don't always follow the assumed logical model or the ignored internals create side-effects that are unforeseen by the original programmer, but exploited by malicious actors.
For example, assumptions about metadata and syntax give rise to buffer overflow or malformed string exploits. In trusting that an input string will be its stated length or follow the official syntax, the programmer adheres to the logical model of the system but creates a vulnerability. Similarly, physical power consumption artifacts can let a cracker guess the state or internal activities of a smartcard encryption chip. The original programmer is unaware that the code creates these artifacts since most coding paradigms ignore issues such as the exact execution time of subroutines, power consumption of CPU instructions, etc.
Becoming security conscious means unlearning all the tricks that let a programmer ignore the complexity inside a system. It means understanding the real behavior of all the internals, all the side-effects, and all the system properties that might be observable or influenceable by a malicious party. That makes programming for security very different and very much harder that standard programming.
To mangle a metaphor, security means that one must peel the onion to ensure that it does not have contain an open door in its core.
Two wrongs don't make a right, but three lefts do.
Well, if you don't really carry anything secure in your luggae, but it has a combination lock when you buy it, you might want a combo like that. I remember my dad's briefcase had combo "000" on its locks for that reason.
Dude, I think I can see my house from here.
Is that warning intended for hordes of Slashdotters with Cable/DSL, or for the webserver hosting the file? Or perhaps its a warning that the hordes of Slashdotters with Cable/DSL won't be able to access it anymore?
...Had this been an actual emergency, we would have fled in terror, and you would not have been informed.
True story.
I needed access to secured room of a building my company was renovating. It had a pushbutton type combination lock on it (or some such). I asked the combination, and the maintenance superintendent said "1-2-3-4-5". I immediately blurted out "1-2-3-4-5? That sounds like the combination some idiot would put on his luggage." Straight Pavlovian response to a Mel Brooks straight line.
It was only after a 5 seconds of being stared at that I realized that the Superintendent had intentionally set that combination, and he was NOT a "Spaceballs" fan.
"As God is my witness, I thought turkeys could fly." A. Carlson
...is posting safe-cracking techniques on /. responsible behaviour?
I read
This one throws a monkey-wrench in the works of the old "hacker vs cracker" argument. If someone is a redneck safe-cracking computer scientist from Georgia, what category do they fall into? Hmmm?
Don't blame Durga. I voted for Centauri.
Similarly, you can have as many security layers as you wish but if you forget to weld the back end of the safe or network on than they still do nothing for security... your only as secure as your weakest point of security.
So I was reading the DaVinci Code and the main characters discovered that the account number for a swiss bank account was the first several digits of the Fibbonaci sequence.
The first thing I thought to myself was:
"That sounds like the combination some GENIUS would have on his luggage!"
Rats would be more funny if they could fart.
And change the combination on my luggage!
Everything I need to know I learned by killing smart people and eating their brains.
the paper looks more like the methods of cracking a lock than to build a dependable security system.
Again, don't click that link unless you do, in fact, want your computer to annouce that you're looking at gay porn and pictures of a chick with sh*t on her face.
Don't leave home without it.
We must be alert to the danger that public policy could become captive to a scientific-technological elite. - Eisenhower
Much of the older stuff is at http://www.archive.org/.
Surely You're Joking Mr. Feynmann has a chapter called "Safecracker Meets Safecracker." It describes his time at Los Alamos during which he repeatedly opened people's safes. (The ease with which he did this actually quite disturbing.) Anyway, at the end of the chapter, he talks about how he learned that a particular lock came factory set at either 0-30-0 or 60-30-60 (I think those were the two), following which the owner would change it to something more secure.
He said he went around Los Alamos after he learned this trying those two combinations and opened about 1/3 of the locks with one or the other.
LOL, assembly language is back. OhYeah.
Pick a corner area of your basement. Build a concrete block room, filling the block voids with concrete and rebar. Put a roof on the block room made out of steel plate, anchored to the block walls, and add another 4" of concrete and rebar on top of this.
For the entrance, use two doors. The inside door should be a vault door (better gun safe door hung on a frame with inside release). Outside door should be steel fire/security door with steel frame and heavy locks. Outside door is just to be time consuming to get to the inside door.
This wouldn't be all that expensive, either, considering a high-end gun safe alone is $5k pretty easily.
Isn't the use of ever increasing keyspace sizes in encryption algorithms (ie SHA256, SHA512, SHAadInfinitum) at a pace slightly higher than Moore's law effectively doing this now?
I can't count how many times I have read "...will take longer than the age of the Universe itself to brute force this /insert encryption scheme of choice here/..." when reading about some new fangled encryption scheme. Naturally, that claim is based on computational power at the time, but doesn't this exactly dispute his claim?
We can be better at it, sure. But computer security systems are designed with at least SOME regard for the notional hacker's motive, opportunity, and skill level.
...But I digress. TREMBLE PUNY HUMANS!ONE DAY MY SPECIES WILL DESTROY YOU ALL!
Just about every gun safe, including my cheapie, that don't have electronic dials have locking mechanical dials. Some have locking bolt retractors, too.
Sure, lockable dials are pickable (and my S&G group 2 lock's key looks fairly lame), but it's one of those additional layer/skill attributes that makes the stuff all the less desirable.
out of the hands of most criminals.
Erk, now where have all those SuperCriminals gone?
It also takes a lot longer. If you're questioning everything the C library is doing, you're going to spend all your time trying to break your own program before you've even written it! Something has to give somewhere.
From the PDF:
There are a few obvious things you can do, like avoiding unbounded reads, trimming down your strings, validating your input, etc., but who's going to think twice about calling fd_set()? Yet there's a vulnerability in the implementation of fd_set() on *BSD which could lead to denial of service or code execution. What's more, it's a tricky and subtle problem which even experienced programmers might miss. (It's also subtle and tricky to exploit.)
(It also affects more apps than the ones listed in the link there, and also affects some FreeBSD, and in theory might affect Linux. I'd post more links, but I'm short on time and long on the to-do list.)
So in short, you aren't going to have time or space in your head to know everything. But if you do the few obvious things, you'll greatly increase the security of whatever you write.
How am I supposed to fit a pithy, relevant quote into 120 characters?
John Dillinger penetrated a bank vault and looted safe-deposit boxes within, but he did it by stealth, finding a closed-down bank, pretending to be an authorized workman, and taking a long time to extract the contents.
When I was a kid, my friends and I put an ordinary paper firecracker inside a wooden box, about the size of a cigar box, and secured the lid. To our surprise, the box spontaneously disassembled itself into its component parts, which travelled outwards at high speed. All of that from a firecracker that would only cause minor burns if you held it in your fingers when it exploded.
Mea navis aericumbens anguillis abundat
I'm a locksmith. I wasn't unhappy. I was simply amazed as to
how naive Matt Blaze was along with some of the other members
of the computer security community.
can't believe there's nobody w/ sense of humor at this time...
If 00000000 is an acceptable nuclear missle secret launch code, then 12345 has got to be NSA-level security!
HIV Crosses Species Barrier... into Muppets
My request for the 2.5 MB pdf was queued for like three minutes, then it started coming through at nearly 2 Mbps.
That sounds like the combination an idiot would put on the atmospheric lock on a planet!
A fine is a tax you pay for doing wrong and a tax is a fine you pay for doing all right.
Part of the theft was getting into some of the best safes in the world. The robbers never even attempted to "crack" the safes... they assumed from the start that they simply could not open the safes w/o the keys. I won't spoil the book for you to reveal more than that.
I've found that my posts don't format quite right w/o a sig.
I wonder if I can go to OfficeMax and get a general "I sue you" form. I bought a nice Trust Fund form and put my car in a trust for my dog.
The programmer is not supposed to assume that they always get the data they expect. Functions exist to take no more then the size of the buffer. There are functions to validate the input and output. You don't have to know every damn thing about a system and you don't have to throw out standard API's, you need less stupid programmers. They need to understand the ideas of the system, not the entire system from the ground up. API's, abstractions and whatever else you can think of are great things, as long as the programmer isn't a lazy idiot who makes far too many mistakes that they shouldn't be making. Being a security minded programmer should not mean reinventing the wheel for everything.
BTW, there is always an 'open door' at the core, otherwise you haven't hit what's being protected, you just hit another layer of security.
"I use a Mac because I'm just better than you are."
Locks, Safes and Security: An International Police Reference Two Volumes is apparently a wonderful book all about the history of lock-picking and its evolution, including ways in which things were overcome. Although the book is a bit pricey.
You could get a new dial with a medeco dial lock. That certainly will add a rather signficant layer to your security, of course this doesnt mean anything if its easy to pull your dial, and drill...
Actually it's pretty stupid, cause it's easily guessed. It sounds like the combination a wannabe genius would put on their luggage. :-)
It's hard to be religious when certain people are never incinerated by bolts of lightning.
Any locksmith who seriously thinks there's information that stays inside the industry *exclusively* is as naive as the customer who thinks their $15 Kwikset is just as good as a Medeco.
Seriously though... that's a good book, it's sitting right here on my bed stand.
Here's a different true story (posted as AC to protect the, erm, me):
The client I currently work at installed similar push-button combination locks on all doors from each floor's elevator hall, and spent a far bit of money on it too.
The combination was set to 7-2-5-3.
Not being a big one for remembering this sort of thing, I idly tried entering 2-3-5-7 - and it opened!
A few tests revealed that their vaunted locks would open with any arrangement of the required four digits - reducing the security from 1 in 10,000 combinations down to 1 in 400 or so.
It's called sarcasm.
The thing is, tried and true inventions like a safe cannot be bettered in a long time. It says something about today's design, versus how it used to be. Gives credence to the old phrase, "They don't make em like they used to".
Amen to that.
Pcvb3
free ipod and free gmail!
Well, if somebody set to stop you shows up at the computer that's being broken into aren't they likely to pull the network cable, or shut down the daemon?
Another valid 5 digit combination that one can say out loud as "1-2-3-4-5" is "24445" (one 2, three 4's, then 5). So there are two possible combinations for "1-2-3-4-5".
Of course, if your lock can't handle multiple digits being the same, well, it's time for a new lock!
What happened to watching a person dial in the code, or planting a security camera? Or, in your "computer science analogy", using a keylogger. People will always be stupid, and sometimes you can even surreptitiously get the smart ones.
Good safes tend to "fail secure" -- that is, when something goes wrong, you can't get into it even with the right combination. The only reason this is acceptable is there's still ways into the safe without damaging the contents. They're expensive (hardened drill bits ain't cheap!), require esoteric tools and knowledge, and hopefully take a lot of time and make a lot of noise, which a cracker doesn't want to do. Encryption, if it fails for some reason, is as hard to break for the legitimate user as it is for the cracker. Fortunately, it doesn't fail that often --- except for good old human factors, like the guy with the key forget it, lost it, or dropped dead.
I never did find out if they fixed my code, I just usd his whenever I needed access.
There was this priest at school who always seemed a bit little out of place wearing clerical vestments. Much to our muted surprise, the combination to his briefcase was indeed 666.
My father who got sent to locksmithing training by the Department of Defense was describing how you drill into the door of a safe to open it if you've somehow lost the combination. Basically you get a piece of metal that is the size of the door from the manufacturer -- it has marks on it where to drill. You drill according to the directions, and then fiddle with the inner workings of the locking mechanism to move the tumblers where they should be in order to open the safe, and to change the combination.
The bad part is that once you've done this, to make the safe secure again you put a steel ball bearing the size of the hole in the hole, and then weld it in there. There is absolutely no way you're going to be able to drill through that steel. Any drill bit you try to drill through it is just going to dance on it, and end up breaking the drill bit.
So I guess in that case, safes that have been forcibly opened using the above method are safer than ones that havn't.
da w00t. mtfnpy?
http://www.bash.org/?431987:
Gear Grinder X: once, we had these total freak seventh day advenist (or whatever) freak ass neighbors
Gear Grinder X: and this girl Lanna was a little younger than me
Gear Grinder X: she was a bitch, and they were all totally religious
Gear Grinder X: she threw rocks at me once on my bike, and so I turned around, and went to run over here
Gear Grinder X: I was hauling ASS, and you know what she did?
Gear Grinder X: put her hands on her hips, and stood there and said "The lord will protect me"
Gear Grinder X: well.... he didn't
There was a burglar in Texas last year that was breaking into city hall buildings all over the state. In almost every one he managed to get access to the safe or safes kept in the building without prying or damaging the safes.
When he finally got caught be debriefed and gave up his MO. He would get in to the building be defeating a usually inadequate door lock with a screw driver. Then once inside he would look in all the desk drawers for sticky notes with numbers on them. In almost every one he would find a sticky note with the combination to the safe. This guy hit over 50 different city halls and got into the safe(s) in almost all of them.
The best safes in the world won't keep people from being clueless about security.
Heck is a place for people that don't believe in gosh.
Has to be the most inventive way to crack a vault. A 20mm canon with AP shells!
They changed the timeclock override password at work from 00000 to 12345 because the button broke from overuse :)
http://www.lockmasters.com/DrillandAccess.PDF
Check out top of page 93.
Too bad for your sercurity idea, although some manufacturers do pack their doors with bearings.
I found this article to be quite diapointing. I don't know where he got that lock or how old it is, but it's likely at leat a hundred years old. They just don't make combination locks like that that would be so easily manipulated. Even a cheap $2 Master pad-lock, as he briefly mentioned in two sentences on page 31, has false gates on the wheels, basically defeating all the simplistic techniques mentioned in the article. Although he states that these false gates are easily identified, trust me, they are not. And drilling into a safe holds no appeal in my opinion, since any competent safe would have appropriate countermeasures. Furthermore, it's just too destructive for my tastes.
I did however enjoy the ever so brief discussion of safecracking terminology. The article would have been a much more more productive use of time, mine and his, and would have also been more entertaining had he discussed the terminology in depth(just read page 4).
A good locksmith specializing in safes doesn't care if you know how safes are opened-- on the contrary, they'll tell you all about it. The job of a competent physical security professional is give the client a straight and honest description of how the product works and what its weaknesses are, and safes are no exception. I've worked for a locksmith for the last ten years and it's company policy to show clients exactly what they're getting and/or what they already have. With safe openings, my boss explains exactly what he's doing and how it all works. Admittedly, there are a lot of locksmiths who think this should all be top secret stuff, but they're just fooling themselves. All the info is out there. There's no official schooling for locksmiths, and no coherent regulation of the profession. Subsequently, there's no way to really keep the information out of the hands of "criminals" while still allowing access for beginners trying to start out in the profession. You can join the Associated Locksmiths of America essentially by just saying you're a locksmith, although you'll be approved for membership quicker if you have the recommendation of an existing ALOA member. Once you have an ALOA membership number, you're a locksmith as far as the "keepers of the knowledge" are concerned. Heck, you don't have to have anything but fifty bucks and a mailing address to subscribe to The Locksmith Ledger, and they frequently have articles on opening various safes.
Really, none of the techniques outlined by Mr. Blaze in the PDF are any big secret. Anyone with access to such a lock mechanism (buy a safe and you've got one) and a little brainpower can figure all that stuff out. The thing is, drilling a safe requires fairly specialized tools and is very noisy. Manipulating a safe requires a lot of practice, and even an expert can take a LONG TIME to get into a safe. There's no astounding revelations there. Walk into my boss' locksmith shop and he'd show you all that. I've tried my hand at both drill penetration and manipulation, and there are no "secrets" that make any of that stuff easy. At best, the knowledge it just makes it possible-- and that knowledge is available through simple observation.
If a job's not worth doing, it's not worth doing right.
so what, he's going to find a fucken horse head in his bed?
Blaze's article just helped me pay for a new dualie 2.5 GHz G5 and one of those cool teevees you hang on the wall. Thanks, /.!
...and I really don't give a flying rat's ass if you're unhappy about it or not. Do you really think there are any things such as trade secrets or unshared knowledge? Welcome to the real world.
So, the cliche movie trick of highlighting the buttons with fingerprinting spray would work in this case, eh?
Sometimes I like to "work around" small issues... http://64.233.187.104/search?q=cache:uKCwKOYICgkJ: www.crypto.com/papers/safelocks.pdf+safelocks.pdf& hl=en
case the link is jacked (shouldn't be...)
Just search www.google.com for.... "safelocks.pdf"
and you will see the ".pdf" file is second hit...
(which is the file that is too busy to download)
so just click on "view as html" and you will use googles bandwidth... ;) they can spare some...
gl and enjoy!
Sea
Why on earth doesn't Slashdot set up a mirror first then link to that instead of bringing down people's websites? Bit/BlogTorrent are free last I checked. Linking to a 2.5MB file?! It's almost like they want the site to go offline.
There was a guy with Tsunami Videos on his blog which ended up costing him $1,000 before he knew what hit him. Does Slashdot compensate those with huge bandwidth bills? or give any warning prior to linking to something like a pdf?
What if Digg added local news and a Slashdot inspired comment karma system? ---
http://houndwire.com
Yeah, I always laught when I see those cheap locking dials. I mean really, how long does it take to pick a 4 pin wafer lock? And like you say, pulling the dial is usually the first thing you do when you drill a safe anyway.
If a job's not worth doing, it's not worth doing right.
Damn, now I have to change my combination!
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
"12345" sounds diffrent from "1234s5". your wrong.
I guarantee you a properly used shaped charge can penetrate that bank vault in minutes. The only problem would be the loud explosion, but I am assuming the thief has the bank held up already and no silent alarm has been tripped. Add a few claymore mines to take care of the first wave of police, and a determined bank robber could get away with it assuming they quickly fled to a country with no extradition. After all, there is no security that can't be bypassed with sufficient explosives.
I see no pretty pictures!
An obvious advantage to using multiple layers of encryption is that if the algorithm used to encrypt one layer is broken, the other layers still offer some protection of the message.
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
The 1959 MIT hackers were, a few years earlier, model-train-hackers.
If you are cracking by hacking, you are a hacker.
"When the going gets weird, the weird turn pro" -- HST
Actually, the S&G lock he showed is pretty much current industry standard design. They're not as easy to manipulate as they sound. The principle is very simple, but the practice is extraordinarily difficult.
Even a cheap $2 Master pad-lock, as he briefly mentioned in two sentences on page 31, has false gates on the wheels, basically defeating all the simplistic techniques mentioned in the article.
They don't generally use false gates on the wheels of safe locks because the fence doesn't ride on the wheels while they're turning. The fence only drops down to contact the wheels when that smaller brass wheel in front is rotated so that thar hook shaped piece falls into it. False gates can make it more difficult to figure out where the real gates are, but the fact that they have a bottom and are not as deep as the real gate make them susceptible to the exact same analysis as a non-gated wheel pack. I think you are not entirely understanding how these locks work and the methods of manipulation he describes.
Although he states that these false gates are easily identified, trust me, they are not.
Trust you? You think an S&G 6730 lock (retail price $115.02, my price $69.01, 5 of them currently in stock at my lock supplier's warehouse in DC-- I just checked their online catalog) is "at least a hundred years old" and expect me, a locksmith with 10 years experience learning from a boss with 30 years experience, to trust your analysis? Please.
--------
Funny you should mention, but those cheap master locks with the false gates is absurdly easy to manipulate. As a locksmith I'll probably be banned from our secret society meetings for telling y'all this; but here, try it at home:
First off, those false gates are only on the last wheel-- the first to wheels are smooth except for the combination notch. Second, the "keyspace" for those master combo locks is a lot smaller than it looks. The dial may be numbered 0 through 39, but you can be within 1.5 in either direction of the correct number and the fence will drop in. For sake of ease of implementation of my manipulation method, I usually round that down to 1.25 because this allows me to divide the wheel into 16 increments 2.5 apart. So effectively the possible numbers are 0 2.5 5 7.5 10 12.5 etc.-- basically each of the numbers marked on the dial face and the halfway mark between them.
So now you have a keyspace of 16 * 16 * 16, or 4096 combinations. This is still a pretty big number, so let's reduce it. Pull up on the shackle and "feel" each of the points where there's a false gate on that last wheel. Around a certain number range it will feel "loose" because these lock wheels are never perfectly round and the fence of the lock will be stopped by the other two wheels. Once you find this loose space, you have a way to check if the other two wheels are correct. If they are, the fence will drop into them and your will feel friction at that formerly loose position. At that point you need only turn the dial until the third wheel gate is aligned and it pops open.
You only need to go through 16 * 16 = 256 combinations on those other two wheels to find the combination. And you don't have to "clear" the lock after each try either: You set the first wheel at (say) 2.5, then spin around to 0 and see if it rubs. If it doesn't turn back the other way again to advance the second wheel to 5 then see if the third wheel rubs. Then go back and advance the second wheel to 7.5 and check the third wheel. Do this 16 times and you've checked all the combos beginning with 0. Reset the lock (4 spins) and try the ones that start with the first wheel at 2.5. continue this process until lock opens.
The longest one of these has ever taken me is 20 minutes.
If a job's not worth doing, it's not worth doing right.
One could weld up around the bearing so that it was at the lowest point of metal. But if you have a torch anyway, just cut the bearing out. There is also a hollow diamond-tip bit shown in Mr. Blaze's paper which might also work well.
And then wrap the whole thing in tin foil. You know, just to make sure.
I don't mean this as flame bait, and no, I'm not a locksmith. However, I have to wonder what, if any legitimate purpose is served by writing and posting such a detailed description of how to exploit safe locks. Seriously, other than knee-jerk "information wants to be free" stuff, is there a serious defence of this?
I'm all for discussion of security, but I read the paper and frankly, this just goes too far.
I wouldn't be surprised if Blaze finds himself in considerable hot water over this, with his employer and with those who are harmed by this.
I'd say from a security point of view you're really safe, since there just aren't good reasons to do this --- and from a program-bugginess point of view, I'd say most C programmers would get it right (assume a fixed sized array and RTFM), while most C++ programmers would screw it up (assume some magic black box).
But yes, your point about such high-level abstractions is well taken.
I walked past the gym we have in the basement of our building. When too maany (non entitled) people started using it, they changed the PIN on the door. I know this because some Brainiac posted a apologetic notice on the door that helpfully included the *new* PIN for regular gym patrons.
Unfortunately it was taken down before I could take a picture of it.
Xix.
"Everything is adjustable, provided you have the right tools"
The perfect safe is a computer controlled one. You can't crack a PIC controlling a solenoid-lock that is deep within the safe. And as long as there is a limit on combinations attempted per second, some sort of automatic combination guessing device is impractical, too.
A slashdotter who didn't build his own computer is like a Jedi who didn't build his own lightsaber.
I'm a locksmith and any locksmith with half a brain should know that all of this is commonly available information. Certainly a few old fogies who think locksmithing is some sort of secret society like the Freemasons would pitch a fit if the customer wanted to see the inside of his safe lock. Or maybe they're pissed because they've been telling customers that the safes they're selling are "impenetrable", but if that's the case then they're the idiots. I have personally showed the various "safecracking" techniques to customers and let them try their hand at manipulating a combo lock. The theory is simple, but the implementation is darn near impossible without years of experience and practice. I've never had a customer decide not to buy a safe because I showed him how they're cracked and he thought it was "too easy". Basically, what it comes down to is that there's no such thing as 100% security. You Can pay more money and add more complication to get "more 9's", but a Star or Horizon in-floor burglary safe will keep out all but the most determined intruder. Honestly, any locksmith that thinks there are any "trade secrets" in the industry is foolig themselves. Anyone can get an Associated Locksmiths of America membership and a business license, and from there buy books that explain it all.
I seriously doubt that posting this on slashdot is going to lead to a massive upswing in safecracking. The one thing I've noticed in the business is that (weird as it sounds) most people are basically honest! Besides, safecracking isn't fast enough for most criminals. Most safe burglaries happen when someone knows the combination, either having been entrusted with it, watching someone else dial it, or finding it written down in a drawer somewhere.
If a job's not worth doing, it's not worth doing right.
For $35USD, and a glance at my driver's licence, I was able to purchase a lock-pick set. I was intrigued, after seeing hundreds of movies showing theives and spies opening doors faster than people with keys.
After alot of research, and pracitice, I was able to open several brands of pad-locks, as well as the doors' to my house. Guess What? It's not as easy as it looks.
I did this mainly out of curiosity, but I recently had a chance to put this new skill to the test.
My neighbor had locked her keys in her house, and asked for my help. After thinking about it for 15 seconds, agreed to help.
I broke a pane in the window of her back door. There was no way I was going to let her know that I was capable of defeating the locks on her house. I have no intrest in breaking and entering, but the fact is, if people know you can do it, and something goes missing, guess who the first suspect is going to be?
I would love to figure out how to open a safe, not because I want to rob anyone.....it's just really cool, and the fun is in learning how to do something most people can't.
Today's show is brought to you by the number 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0: 25
They're actually only marginally safer. Not only are there bits that can go through ball bearings (as another poster noted), but there is more than one place you can drill to see into the lock case. You can even drill at an angle and get UNDER the ball bearing. So long as you notice that it's been drilled before, it's doesn't add any difficulty.
If a job's not worth doing, it's not worth doing right.
Of course, abstractions have a very important role in crypto-security. We don't yet have a widely used, practical notation for secure networks and protocols. Its easiest to thwart things like man-in-the-middle attacks from the start with abstract reasoning of what handshakes and protocols need to do. Naturally, there will be a dischord between the abstract model and the implementation. Nothing can move us seamlessly from one to the other, but human thought and effort can bring us the closest.
I agree at a fundamental level, it takes effort on all levels and aspects to create a solid security system. To borrow a metaphore from Seven Samurai "Defense is harder than attacking."
I Browse at +4 Flamebait
Open Source Sysadmin
Ok, have fun Vlad.
So we slashdotted a DNS server (I don't really believe we are that big)?? Or is it the feds trying to prevent us from getting "sensitive" materials?
Have a Happy new year y'all!
-ItsME
That's what I get for trying to act like a typical arrogant know-it-all slashdotter even though I don't know what I am talking about.
A. Coward
The author of this is seriously named "Matt Blaze"?
It says he/she is a professor and names the school (Penn Univ), so maybe it's a real name but it sounds like a pseudonym.
Anyone know for sure?
Good writing style (the old hamburger essay, IIRC!) says that details that do not directly support the main point of a paper should be edited out, and by those standards, this should have been a very short paper! (although admitedly much less interesting to Slashdotters and much less fun to read)
I almost get the impression that this paper was written primarily because the author finds safe-cracking to be a cool hobby to write about, and then he retrofitted it into a computer science context in order to present it at a computer security conference. This may also help to justify it and to keep people from criticising it for being a how-to guide to safe-cracking (like the infamous MIT guide).
-- Marcio
Now I could see lazy users setting the combos to something easy to remember like 60-30-60 or such, but they don't come from the factory with either of the two settings you mentioned.
I'm too lazy to compose a creative sig.
The parent post was not a complaint about the information being distributed. It was a complaint about how the information was being distributed. There's a difference between making the information available to those who go looking for it(as Matt Blaze did with the .pdf,) and posting a link on Slashdot for thousands of people to see. The atmosphere I have been surrounded by has been to appreciate that physical security is a touchy subject and to tread lightly. If for no other reason than to avoid these stupid debates about the merits of security through obscurity.
I think stating that I do not consider myself among the pissed off locksmiths and have nothing but respect for Matt Blaze might make the original post's intent more clear.
http://www.timhunkin.com/94_illegal_engineering.ht m
Rich.
libguestfs - tools for accessing and modifying virtual machine disk images
Tim Hurkin , a british boffin ,explains things a tad more plainly in this excellent piece of his.
. ht m
http://www.timhunkin.com/94_illegal_engineering
Wanted : A Signature.
Or maybe he didn't want the public at large going around trying out these two combinations and opening safes?
"Some names have been changed" etc...
+Pete
Score:-1, Funny
But who knows if the combined algorithm has a flaw that neither algorithm had, separated?
As for simple layering the same protocol, consider this (silly example): Exchanging each letter with the letter n positions futher along the alphabet does not get more secure by being done multiple times.
The same holds true for 3DES and every asymetric encryption method I have seen.
Religion is regarded by the common people as true, by the wise as false, and by rulers as useful.
I tried that myself with my new Quanilon(tm) quantum CPU from AMD. The problem I had, was when the cooling fan failed the CPU overheated -- causing the probability wave to colapse -- and my cat died...
Required reading for internet skeptics
And it is frighteningly common, also I wonder why everyone is forgetting the 3 keys to identiying
1. Something you know
2. Something you have
3. Something you are
For any moderatly secure setup, pick atleast 2
Remember 3DES does just this, it is DES 3 times applied (using 2 keys, one used for cycle 1 and 3 and one for cycle 2)
I believe the original poster simply misremembered the combinations mentioned in the book. My memory may have been corrupted by seeing your post, but I'm pretty sure the combinations in this story were 50-25-50 and 25-50-25.
Oh wow, I love Amazon. Find Surely You're Joking, Mr. Feynman! on Amazon and use the search function to look for "Safecracker meets Safecracker". Click on the last link on the first page, and you can find the exact text. The combinations in the book are actually 25-0-25 and 50-25-50. It also turns out that it only opened 1/5th of the safes, not 1/3rd. That book search rules!
Mod down posts with a "Free Mac Mini/iPod" sig, they're spam!
I do agree with the other points though.
Okay... I'll do the stupid things first, then you shy people follow.
[Zappa]
Bah. A real genius would set his combination to the LAST few digits of the Fibbonaci sequence ;-)
--- Egads, I glow in the dark!
- Adding layers doesn't make it any less secure,
- Adding bits to a single key in the letter-shifting method by itself doesn't make it any more secure, and
- Stacking that encryption method and a second method, each with a key size of n/2, will probably be more secure than using the letter-shifting method alone with a key size of n.
Your example caused me to think of a simplistic case where a combination of methods, each with a key size of n/number-of-methods, may be less secure than a single method with a key size of n: your letter-shifting method combined with a simple XOR method. In this case, it may be true that the combination is less secure than the XOR method by itself with twice the key size.This is due to the fact that the letter-shifting encryption method does not benefit at all from a larger key size, and thus taking bits from the method that does benefit from a larger key size to give it to a method that does not, will of course cause the security of the system as a whole to decrease.
It is still more secure, though, than the letter-shifting method taken by itself.
Now, let's assume that the flaw in the letter-shifting method wasn't discovered unitl after it been used for a few years.
We now have three types of encryption systems (relevant to this example):
- The system that used letter-shifting by itself, with key size n.
- The system that used XOR by itself, with key size n.
- The system that used the letter-shifting method in combination with the XOR method, each with key size n/2.
After the flaw in the letter-shifting method is discovered, the people who used letter-shifting by itself are totally screwed, those who used XOR by itself are unaffected, and those who used the combination are partially-screwed.I'd rather be partially-screwed than totally screwed.
The thing is, it's not possible to tell in advance whether or not a single encryption method is flawed.
(If it were possible, such a method wouldn't have been used in the first place.)
Using a combination of different methods is a way of avoiding putting all of one's eggs in one basket.
Can anyone state a case where a combination of encryption methods, where each has a different key of size n/number-of-methods, is demonstrably less secure than each and every one of the methods used by itself with key size n?
I don't see how a chain of methods could be any weaker than its weakest link, even when the weakest link, used by itself, would have a larger key size.
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
Well, at least that would give me something to do with the pile of fingers I've been collecting.
Well, I'll try to explain why people think what you are proposing is suboptimal.
Firstly, I think you have misunderstood what "adding extra bits" (enlarging the key) means --- at least in this context. In my (silly) example, the key had the length of 1 (number). Notice there is no bits, since the atomic unit in this encryption unit is letters. If you increase the number of bits we would have more numbers.. E.g, (1,2) would make "have" into "icwg", which would be harder to break. The scheme is actually not THAT bad --- there are methods to break this sort of encryption, but it isn't trivial. A person that has not studied cryptography would be pressed to break something like this, at least if the key length is unknown.
If you take this method to an extreme with keys longer than the text, you would have a fair encryption method, provided that the keys are kept secret. But nevermind that.
Now, to invent another cryptographic method, let's consider a method where the positions in the alfabet are multiplied rather than added, and the modulo of 26 is taken. So for the example key (1,2) and the word "have" the result would be "hbvj".
How secure are these methods combined? Well, if the coded and original letters have position x and y, respectively, and we are using keys k,l with values k_1, k_2, ..., k_n and l_1, l_2, ..., l_m, where n and m are some integral numbers. Then the effort spend on encrypting the message is O(n+m). The effort spend decrypting then will only be proportional to the smallest common multiple of n and m --- it's an easy proof, so I leave it as an exercise. However, for the same effort you could have obtained and effort proportional to the multiplum... and the encryption and decryption rutines would be simpler, and thus less errorprone. That's one argument against layering encryption algorithms.
Now, either of these algorithms may be weak --- indeed, the muliplum algorithm is for a number of reasons, most importantly the distribution of the resulting letters is not uniform. Note that if the addition is performed first, no harm is done by this, but if the multiplication is performed second, the distribution would be skewed in such a way that the addition key could be guessed from the distribution of the letters of the encoded message. This would render the combined algorithm weaker then the addition alone. This is the "real world" example you asked for... and admit it, it is not that far-fetched for a slashdot comment ;-)
Disclaimer: I'm not really a crypto guy, just an IT specialist + mathematician.
Religion is regarded by the common people as true, by the wise as false, and by rulers as useful.
The problem with your $2 Master padlock is that is is easily opened with a $.02 piece of metal stuck in to the lock through the shackle hole. There's no need to know or guess the combination, or to even touch the dial. Opening the lock this way leaves no trace.
If you want, simple: blowtorch. Melt the dial and internal mechanisms. It takes about 20 seconds and works every time.
Article X: The powers not delegated... by the Constitution...are reserved...to the people
Not really. The key size is a measure of the number of different ways a given algorithm can encrypt an input. In the case of a simple caesar cipher (shifting each letter by a fixed amount), there are 26 different possible keys. Therefore, the keysize in bits is log_2(26) = 4.7 bits.
Sorry for nitpicking, but I am a bit of a (strictly amatuer) crypto guy.
Information doesn't want to be anthropomorphized. -AC
In physicist Richard Feynman's book, "Surely You're Joking, Mr. Feynman," he talks about working on the Manhattan Project in New Mexico. He discovered he could figure out the combination to the safes they were using just by touch. So he went around to various offices and would kind of lean on the safe while chatting with the inhabitant. He'd twiddle the dial as though he were just playing around with it during the conversation, but he was really determining the combination. Eventually, he went to the security people and showed them how easy it was to crack these things, and showed how he had the combinations to many safes. Instead of improving the safes, the response of the security people was to make the occupant of every office Feynman had ever been in change the safe combination. The inhabitants were none too happy, and to avoid a repeat of the episode banned Feynman from entering their offices thenceforth. The safes were left as vulnerable as before.
While I was working delivering a free weekly paper in Sarasota, Florida, I noticed a funny pattern amongst the gated condo communities on the keys.
When I started the route, I only had the code for some of the condos, so the first few weeks I just left a bundle of papers at the condo gate for the others. We got some calls about it, and two of the places mentioned they had a master code of "1-2-3-4". I started experimenting, and it turns out that almost every gate on the keys will let you in with "1-2-3-4(-5)" or "9-8-7-6(-5)".
This seems to be consistent everywhere else I've tried since. Seems like these gates would be rather expensive to put for just an illusion of security.
Personally, I think mass public distribution is better. It better serves to destroy the "security through obscurity" mindset held by a lot of locksmiths. It's not like any of that information is a magic back door that lets one defeat safes with the wave of a hand. It's a straightforward and honest examination of the design limitations inherent in these locks. It shouldn't be "kept quiet" so that only those who think to go looking for it find out; everyone considering these for physical security should know about it. The very fact that there are locksmiths out there who think this should be kept quiet is why this needs to be broadcast as publicly as possible, because people clearly can't depend upon those particular idiot locksmiths to tell them what they have the right to know.
If a job's not worth doing, it's not worth doing right.
I don't think that wafer lock is intended to slow down a serious attacker. Rather it's intended to stop someone who has daily access to the outside of the safe from trying every combination over time. Typical situation - kids and gun safes.
Please explain to me what 0.7 bits is? ;-)
Sorry for nitpicking, but the above statement is rather silly, unless you can think up a way of generalizing the definition of a bit to include rational numbers ;-)
As we both know, this is toally besides the point :) The point of course, was that by more bits we don't mean shifting the original letters more, we mean shifting the letters in more ways. Eh. Approximately.
Religion is regarded by the common people as true, by the wise as false, and by rulers as useful.
Just an observation and maybe some food for thought. But he's not really causing problems. He's only pointing out that security via obscurity is not security. BTW did you know that Feynman's favorite pastime was safecracking? BTW you do realize that the study of almost anything is reverse engineering, don't you? Physics, math, whatever. So where's the problem? Why is reverse engineering of one thing considered a problem while reverse engineering of something else is not?
http://tinyurl.com/3t236
[...]locksmiths would rather you didn't know about[...] As for me, they can rather as long as they.
You said you were a mathematician, and I'm not much of a crypto guy either, though I am confident about what I posted. I'd recommend going to the source and getting the full math treatment.
:-)
There is a dichotomy between the level of math I am talking about and level you were. I was talking mostly pure math and saying it may or may not apply practically, you're starting practically and trying to argue up to the math. If you're a mathematician, you should know how good that idea is
The trivial example is, for instance, ROT13, which decrypts itself. Apply it once, and while by modern standards that might as well be plaintext, it is slightly harder to read. "Layer" it with ROT13 again, and now you've decreased the security, not increased it.
"Layering" Ceasar ciphers does nothing to increase the underlying security of the encryption, though unless you get very unlucky or careless it won't "undo" the encryption. All layering does is change the ultimate symbol matching table and all "layers" can trivially be decrypted in one fell swoop; a modern attacker won't even have any way to know there were layers in the first place, they are so transparent!
On the other hand, it is widely thought that while DES had an excessively small keysize, the algorithm was reasonably secure enough that you could layer it three times for 3DES and get a "new" algorithm that is still useful.
I'm sure that modern encryption has been scrutinized for this sort of weakness, but even so, it's the kind of thing that ought to be instinctively repulsive mathematically; when you composite two encryption forms together you are basically creating a new one, with unknown characteristics. Any monster can pop out of the folds of math-space and bite you. Better to stick with what we mostly know about.
Also, fractional bits pop up all the time in info theory and encryption (a branch of info theory). One example of a fractional bit, though not related to encryption so much as error correction, is a value that you know is either one or zero, but you only know it is a one with 90% confidence. That isn't a full bit, but neither is it zero bits. Happens all the time. In fact, technically, in the real world we never deal with bits, as we can never be 100% certain. Inside your processor it is so close to 100% as to make no difference, but as you get out into the world the uncertainties can reach our threshold of conciousness, and fractional bits is the most natural way to work with error correction situations.
Yeah, yeah, this is what I get when I decide "I won't need that book over break" and leave it in my dorm room at college so I can't remember exactly what the specifics are. Didn't think to check Amazon.
The books he references aren't exactly easy to get hold of... anyone know if there are any torrents or downloads of any of them that might be in the public domain? (or maybe illegal ones..)
Muhahahaha!! Can you say........ SLASHDOTTING!! 8}
Read my blog: HansMast.com
Sigh. What you wrote is essentially meaningless --- at least I can't see how to generalize the definition of a bit. A bit is a (state) variable with two possible values. I don't know if you could possible make this an dimension in an outcome(?) space, then approximate the dimension the way the fractals guys do (which I think is nonsense, and seems to have fallen out of favor, but hey) and thus arrive at fractional bits. I'm sure the result would be very different from what you imagine in any case.
And it is not just my lack of capacity to understand weird things. But you cannot represent 26 different states with 4.7 bits --- it's nonsense. You need 5 bits. That's the long and short of it. Now, I understand what you mean. You are saying that the strength of a key is defined as the number of states it can hold, and thus a key of 5 bits has a strength of 32, whereas an key containing 1 letter would have a strength of 26, the way I put it earlier. And certainly, I could have defined the strength of a key as the log_2 of this number, arriving at your 4.7 number. That is why I said I was nitpicking. I think this is where you have been confused, though it is hardly catastrophic.
I am a mathmatician, you can search for my master thesis if you want --- though it is in danish, so I doubt you would understand any of it. It is on the subject of approximation of topological spaces (using normal coverings). A "dichotomy", indeed ;-) Separating mathematics from reality is one thing, but separating it from reason is quite another! If you want fractional bits, you need a definition, and a definition that makes some sort of sense. At the very least, the definition should imply the current definition for integer numbers.
Snipping a lot of trivia...
I don't know about repulsive, but you hit the nail on the head with the new alghorithm thing.
You are, I assume, referring to "fuzzy logic" here. Now, such a state variable is usually defined as a real number between 0 and 1, and so the value of the such a bit might be 0.7, or whatever. You could even say that the average number of bits with a value about something is 23.3, but then we are talking about an average number of bits, which is a quite different beast than the number of bits.
Religion is regarded by the common people as true, by the wise as false, and by rulers as useful.
We used to "open" them in Jr. High by striking the dial at a sharp downward angle with a normal red brick... Not sure if actually breaks the mechanism or just pops the shackle past the detent that holds it in place, but it worked every time and usually popped the lock with a single strike.
-*The above statement is printed entirely on recycled electrons*-
Sorry - it's Information Theory. There are 4.7 bits of entropy (in an information theory sense) in a natural number chosen with equal probablilities between 1 and 26. Hence, the statement that there's a key size of 4.7 bits.
To see what that means, suppose we were had an alphabet of 1000 different letters. It'd take much longer to brute-force reverse the cipher and discover the key. And, even more time if we had an alphabet of 1 million letters. (The key sizes in these cases would be 9.97 bits and 19.93 bits.)
Of course, there are much better ways to break this sort of simple cipher than brute force. But, I hope that gives you some idea what the key size means.
Information doesn't want to be anthropomorphized. -AC
Yeah. Murder/attempted murder of a "wave" of police is surely worth the $100K or so, at most, you'll get out of the heist. There really aren't that many hops between "no extradition" countries you can make before you're painted into a corner.
There's really no point in robbing a bank at all, unless you're either stealthy enough to do it right or you're ready for your life to be over afterwards.
I am well aware of the concept of entropy :)
But unless you define a term "key size" to mean "the entropy of a sequence of randomized keys" the second paragraph is just meaningless, if I was to be in nitpicking mode.
But now I tire of this discussion. Thanks for your part...
Religion is regarded by the common people as true, by the wise as false, and by rulers as useful.
As for simple layering the same protocol, consider this (silly example): Exchanging each letter with the letter n positions futher along the alphabet does not get more secure by being done multiple times.
That's true, but:
1. Adding layers doesn't make it any less secure
I would say that rot13, while insecure, when adding another layer would make it less secure.
It's the same as with the default admin accounts on networking gear. You install the gear, configure it, then set or change the password.
And anyone who goes to the expense of purchasing a security container (particularly the GSA ones Fenyman would have run into at Los Alamos) who does not ensure that proper combination security procedures are followed is a fool who deserves to loose whatever was kept in the container. As well as suffer the legal penalties if the contained items are sensitive in nature.
I'm too lazy to compose a creative sig.
> A real genius would set his combination to the LAST few digits of the
> Fibbonaci sequence
I prefer the last digits of the 42nd root of the base of the natural logarithm.
Cut that out, or I will ship you to Norilsk in a box.
> Funny you should mention, but those cheap master locks with the false gates
> is absurdly easy to manipulate. As a locksmith... The longest one of these
> has ever taken me is 20 minutes.
I find it interesting that a locksmith, of all people, thinks it could ever
concievably take this long to open one of those things. Of course, it is
your knowledge of the internals of the lock mechanism that is tripping you
up. There are much faster ways to open those things than turning the dial,
feeling friction, and deducing the combination. No, I don't mean bolt
cutters. You can do it so that casual inspection and even use of the lock
afterward will probably not discover what you've done, although the part
of the lock that hooks onto the thingydoo inside gets worn out and the lock
starts to feel very loose if you do it to the same lock too many times.
If you still don't know what I'm talking about, no more hints: go find
any eighth-grade boy whose favorite subjects are gym and study hall, hand
him a locked $2 Master lock, and say, "I'll give you ten bucks if you can
open this in under one minute with no tools except what you've got on you."
Cut that out, or I will ship you to Norilsk in a box.
No, you'd just avoid using select() altogehter ... because it's annoying as hell anyway, poll() is much easier to write with, and to optimize. As are the newer epoll/kqueue etc. which are also much faster, for most cases.
It's the same with other things, you don't "just validate your C style strings" ... you have real ADTs that don't have major security problems if you read NIL bytes off the network, or need to add data to the end of the string.
ustr: Managed string API with ave. 44% overhead over strdup(), for 0-20B
Sigh. What you wrote is essentially meaningless --- at least I can't see how to generalize the definition of a bit.
:-) ) one.
.5 bit floating around, but the protection the algorithm and data would provide is neither 1 bit nor 2: 1.5.
I'm pretty sure you are talking about what would be the great-grandparent to this message, and that's not me.
You are, I assume, referring to "fuzzy logic" here.
Not necessarily. Let's try this: A bit, fundamentally, is a statement of knowlegde of a binary proposition. A 1 means that you are fully confident it is true, a 0 means that you are fully confident it is false.
Is that the only definition of bit? Hell no! But what fundamental math concept only has one applicable definition? (Is it just me or is discrete even worse than continuous this way?) Certainly as I said it is useful. Fuzzy logic is one case, but not a very exciting one since it was shown to be equivalent to non-fuzzy logic; error correction is a much more relevant, albeit practical (i.e., not "mathematical"
Obviously the idea of a fractional bit falls right out of this probabilistic definition; it's something you only have a probability for, not a certainty. But it can come up in other contexts too; there is a measure of entropy which naturally gives fractional bits. It is easy to create a parity scheme for data transmission that provides 1.5 bits of protection; a one-bit error is guaranteed to be detected but a two bit error has a 50-50 chance of going undetected. (Nothing like that is in use AFAIK, probabilistic detection was pure anathema to computer science until fairly recently, but one can be constructed.) Here, it is not that there is a
Fractional bits are like QM superpositions; you're right in the sense that they can't be "observed" (for some suitable definition of "observed"), and thus in way they aren't "real", but without them a lot of math "stops working".
As for the way that other guy tried to use it, at this point I don't even remember, so I can't speak to whether he used it correctly. I was just trying to clarify my original point with solid examples and take a shot at explaining fractional bits. I'll also re-recommend going to the source on this one; a full understanding of encryption is something few people even can obtain and even fewer can dedicate the time, but for an experienced mathematician, the introductory terms and definitions are fairly easy and, at least in the computer domain, actually quite useful as thinking tools. I only wish I could point you at a free online source easily... well, let me see... well, this is a start, I guess, though it is so ugly in plaintext it is hard to read and didn't have what I was hoping for, but I'm not sure anything like that would be online anyhow... at any rate, the algorithms and crack techniques have passed beyond what any Mere Mortal could hope to understand or contribute to in any reasonable time period, but the basics are quite basic.
rot13 doesn't use keys.
Care to explain?
"That sounds like the combination some idiot would have on his luggage."
I'm not an idiot, I just can't remember numbers that aren't in sequence.
I don't know the details of how it's done, but I know that junior high school
students can open those things without the combination or any special tools.
It's colloquially called "kicking locks", but, not having seen it done, I'm
not certain actually kicking the lock is how it's done. Might be, though.
Anyway, although I've not actually been present when it happened, I did have
the lock on my locker kicked a couple of times. And don't say they watched
me unlock it and got the combination, because if they'd watched me open the
locker, they'd have known the latching mechanism on mine was broken and
taking the lock off wasn't necessary. The first time it happened I found
the lock locked onto one of the banister rungs on the stairwell (which was
common; there were always half a dozen locks on different rungs there).
The second time, I never found the lock.
And I don't think they fiddled around with turning the dial for twenty
minutes, feeling friction and getting the combination, either, because my
locker was directly across from the office, and we only had four minutes
between classes.
Cut that out, or I will ship you to Norilsk in a box.
Yes, the spring loaded latch mechanism can be "kicked", as you call it. It's essentially a design flaw in the mechanism. It really only works on older master combo locks or newer ones that are worn. A sharp blow at the right angle will put pressure on the shackle and also cause the latch to pull back just a bit-- done just right, the lock pops open. It can also potentially damage the internals, so I generally don't bother trying it. If I'm allowed to break the lock, a die grinder with a cutoff wheel will slice the shackle like butter. If I need the combination for a Master combo lock I can just look it up in the code books based on the serial number. The manipulation method I described is something I came up with one afternoon to amuse myself. Last week I figured out how to open a TSA approved luggage lock without tripping the tamper indicator. Locksmiths are weird.
If a job's not worth doing, it's not worth doing right.
So, cracks in one layer might reveal enough information to break the next layer. Or, a break in an inner layer may compromise the security of the outer layer. For a physical analogue, see the book "Surely You're Joking, Mr. Feynmann," and specifically the part where he fiddles with people's already open safes to learn their combinations.
Here's a possible example. RSA has an encryption method called OAEP. This page notes "to construct a valid OAEP encoded message, an adversary must know the original plaintext." Let's say that Eve manages to find the plaintext of one message (perhaps through dumpster diving, or whatever.) She might now be able to create OAEP encodings that can spoof the inner layer. By introducing them at the right point in Bob's stream, he may believe that they're valid. Or, Eve might be able to use her computed OAEP encoded message as a plaintext crib to help her break the outer layer's key.
Sure, there's a lot of "what if" there (of the sort cryptographers love to endlessly debate) but the point is that "stacking" algorithms is not an automatic guarantee of "more" security.
John
Those "old style" Master locks had knurled steel knobs, as opposed to the single cast knob and plate common today. It was commonly known that by pulling up on the shackle that you could "feel" the last digit. At that time they did not have false gates on the third wheel. Knowing the last digit, I started by spinning right to zero, left past zero to the first "pickup point" for the middle wheel (again, very easy to both feel and hear in those old locks) and back to the known final digit. If it failed, I'd spin left to 2.5 before the previous number (moving the middle wheel back one test point,) and back to the final digit again. I found the entire first digit test could be performed in less than a minute with this method, so I continued. In 15 minutes, I had the lock as my prize.
In junior high, it was also common for kids to forget to secure their lock in their gym locker. The penalty paid if someone found your lock hanging open was that they clipped it to an overhead pipe, along with several dozen other forgotten locks. I found that pipe to be a rich bounty of locks that I opened, took home and later took apart. My goal was to locate the "drill point" out of some fanciful notion that if it worked in the movies, I could do it too. I did map out the point at which to drill them, and then discovered I could drive a nail into the mechanism at a certain point in the back and it would pop right open. Of course, hammering sheet metal wasn't much of a challenge, so I then found I could carefully pry off the thin backplate, examine the wheels, and replace the backplate (poorly.) In the end, though, spinning the dial was the most satisfying method of opening the locks.
Around that time, Master came out with the notched 3rd wheel (probably because I couldn't have been the only kid to open their locks.) It wasn't for several years that I dared to try one, but then found I could brute force the third digit almost as quickly as spinning it back to a known number (the false gates were quick checkpoints.) It was then that I discovered that the latch would pull "farther" for certain second digits, and it was about that time I realized it hinted that my second number was probably correct, saving lots of time in the brute-force arena. If only I had realized that in the era of non-false-gated old locks, I probably could have opened any of them in about a minute or two.
One other lock-related thing I remember vividly from the mid '70s were the TV commercials featuring a Master padlock clipped to the center of a large bullseye, and a .30-06 rifle being fired through the middle of the lock. The lock held, of course, and we viewers were supposed to believe that "proved" Master Locks couldn't get shot open, and that any lock shot open on a TV cop show must have been some other brand. I smiled, of course, since I had already filed off the wards from my cheap padlock key and had made a master key that would have opened the TV lock quicker than the original key.
It still takes me around 4-5 minutes to open any of the modern Master combination locks these days, and I'm just a programmer who likes to have "finger puzzles" -- no experience cracking safes here!
John