An encryption that would scramble copied docs?

[Tiktaalik]

Is there some kind of encryption that would cause documents to become permanently corrupted if they were copied onto another drive? Or something similar?

I don't need to do this, I'm curious about it for a storyline, and I'm not savvy enough to be able to figure out the possibilities myself...thanks for any info!

 

[Brian-M]

You could use the drive's serial number and the file's position on the drive as a seed for a pseudo-random number generator whose output is used as the key. Copying this file to another drive would result in the file being unable to be decrypted....

... unless you were savvy enough to copy this information as well, and open the file with a cracked version of the decryption program that uses this copied data to seed the pseudo-random number generator instead of the actual serial number and file position.

 

[Tiktaalik]

That's the kind of stuff I'm looking for, thanks!

 

[Cuddles]

You could use the drive's serial number and the file's position on the drive as a seed for a pseudo-random number generator whose output is used as the key. Copying this file to another drive would result in the file being unable to be decrypted....

File position would be a risky one, since things like defragmenting or load balancing could potentially change that even when no-one is doing anything to the file. Probably best to stick with hardware, as is already done in some cases.

 

[abaddon]

Haven't seen them used in a long while but maybe a dongle might be the thing. The ones I had plugged into ye olde 25 pin printer port on your computer. Without the dongle plugged in the software simply would not run and without the software you couldn't read any documents/user files.. You could copy files to another computer, and they would still be identical to the originals, you just couldn't do anything with them, not even read them.

 

[Rasmus]

That's the kind of stuff I'm looking for, thanks!

Read digital Fortress by Dan Brown.
Once your eyes have stopped bleeding and your doctors have the brain tumour under control, get used to the idea that he's talking complete bullocks throughout.

A file is always the same. If I can make copies, it's mine to keep.
Decrypting it will not be any more easy or complicated if part of the key is taken from the hardware, or the date at time of reading, or the lunar phase at the time of the creation of the document.

At the end of the day, it's all just numbers.

Of course ... I can whack you over the head until you tell me a password. But if you tell me "the password is the drive ID of the original drive ... you know, the one that burned in the car crash after the chase where you abducted me?" I may have a small problem on my hands. (I'm still gonna hit you, of course...)

 

[abaddon]

Read digital Fortress by Dan Brown.
Once your eyes have stopped bleeding and your doctors have the brain tumour under control, get used to the idea that he's talking complete bullocks throughout.

I LOLled. As I posted before, the only book I have ever read that had me shouting and ranting out loud.

A file is always the same. If I can make copies, it's mine to keep.
Decrypting it will not be any more easy or complicated if part of the key is taken from the hardware, or the date at time of reading, or the lunar phase at the time of the creation of the document.

At the end of the day, it's all just numbers.

Yep.

Of course ... I can whack you over the head until you tell me a password. But if you tell me "the password is the drive ID of the original drive ... you know, the one that burned in the car crash after the chase where you abducted me?" I may have a small problem on my hands. (I'm still gonna hit you, of course...)

I think that's called percussive decryption?

 

[Dessi]

Is there some kind of encryption that would cause documents to become permanently corrupted if they were copied onto another drive? Or something similar?

I don't need to do this, I'm curious about it for a storyline, and I'm not savvy enough to be able to figure out the possibilities myself...thanks for any info!

Sounds like you're describing some kind of DRM. On DVDs, it works somewhat like this: DVD is encrypted/decrypted using a proprietary algorithm. The secret key lives in the lead-in area of the DVD, which is not usually included in a bit-for-bit copy of the DVD, making copied DVDs unplayable.

(Note that this doesn't actually stop people from copying DVDs, partly because the algorithm was broken in 1999, uses tiny keys which can be brute forced in seconds, and the decryption key is physically printed as part of DVD itself.)

I'd suggest some kind of hardware which approximates a one-time pad. Use random noise to generate a key which is at least as long the encrypted message, which you can use to securely encrypt the plain text. You can generate a new key, and repeat this process again, so that the message is only readable if a recipient has *all* the keys.

The hard part here is securely transporting the key(s). One more agents can physically carry the key with them, or perhaps the key can be transmitted via SSL to the recipient.

That said, no technology in the world can resist an unwitting schlub just *giving away* the information. "I'm the president of the KGBluuhh---the CIA! And I need Top Secret XYZ message immediately!" "What? I can't do that?" "I'm the president! Do what I say or you're fired!" "Right away, sir!"

 

[abaddon]

Hey, OP, I don't want you to give away your entire plotline, but some extra hints might help.

Here's another suggestion. All documents are stored as polymorphic viruses. IOW, they are executables. to read them, one must execute them on the target machine. Executing them internally alters the file according to <insert method/algorithm of choice> or destroys itself, even, if it happens to be the wrong computer/HDD/<insert hardware of your choice>.

Handy side effect -you can bot the other computer for spam/hacking/taking over the world whatever the story line requires.

Down side, you need a compelling reason for people to execute it and/or a covert way to have it unwittingly executed. Then again, viruses do this by many means in the real world.

 

[Tiktaalik]

Hey, OP, I don't want you to give away your entire plotline, but some extra hints might help.

Here's another suggestion. All documents are stored as polymorphic viruses. IOW, they are executables. to read them, one must execute them on the target machine. Executing them internally alters the file according to <insert method/algorithm of choice> or destroys itself, even, if it happens to be the wrong computer/HDD/<insert hardware of your choice>.

Handy side effect -you can bot the other computer for spam/hacking/taking over the world whatever the story line requires.

Down side, you need a compelling reason for people to execute it and/or a covert way to have it unwittingly executed. Then again, viruses do this by many means in the real world.

Let's say one or more people are keeping information of an incriminating nature on a particular computer. Another individual, thinking to blackmail them, copies all the files off the computer. However, when the people to whom he gives them try & read the files, they're too messed up to be deciphered. Something along those lines...

Please be gentle. I have limited understanding of computereze! I'm just trying to suggest enough info to make it believable, I don't need to go into a lot of detail. Just so someone who's reading it won't go, "Oh, that wouldn't work!" and ruin their suspension of disbelief.

Thanks for the answers so far!

 

[Brian-M]

Let's say one or more people are keeping information of an incriminating nature on a particular computer. Another individual, thinking to blackmail them, copies all the files off the computer. However, when the people to whom he gives them try & read the files, they're too messed up to be deciphered. Something along those lines...

Maybe the files are encrypted so that a security token to read them? Since only the authorized users will have the security tokens, the files are useless to everyone else.

 

[Blue Mountain]

People copy files a lot more than they realize. For example, when you open a file in a word processor or a text editor, open a PDF for viewing in a reader program, or open a picture for viewing, what you're really doing is copying the file off the disk into the computer's memory, and the text editor or picture viewer is working with the in-memory copy. This is also true of the internet: getting a file such as a web page or a picture over the internet involves making a copy of that file off the disc, then streaming that copy over the internet to your computer.

If the protection scheme scrambles the date as it's copied off the disk, you'd never be able to view the files on the disk because they'd be scrambled even before the editor/viewer program got a chance to work with them.

So what you need is a program that silently (the term used in the computer industry is "transparently") corrupts/encrypts the data as it's being written to a removable device, such as a USB thumb drive, a streaming tape drive, over a network, or (if you're old enough to remember them) a floppy diskette. The important thing here is the files get encrypted any time they're not being written to the local hard drive.

Once the files are on the removable device, the only way to read them is to know both the cipher and the key that was used to write the files, and use a decryption layer to read them.

It appears there is already something like this available in some versions of Windows: Using BitLocker to Encrypt Removable Media

 

[Tiktaalik]

I see - the encryption would happen during the writing rather than the copying/reading. That would work. I'll have to check out BitLocker, thanks!

 

[abaddon]

Let's say one or more people are keeping information of an incriminating nature on a particular computer. Another individual, thinking to blackmail them, copies all the files off the computer. However, when the people to whom he gives them try & read the files, they're too messed up to be deciphered. Something along those lines...

Please be gentle. I have limited understanding of computereze! I'm just trying to suggest enough info to make it believable, I don't need to go into a lot of detail. Just so someone who's reading it won't go, "Oh, that wouldn't work!" and ruin their suspension of disbelief.

Thanks for the answers so far!

I see your problem. The blackmailer must be able to read them but not pass them on in any way. Or maybe in any verifiable way? Surely if the blackmailer can read them he can equally pass them on via word of mouth, screenshot, phonecam shot of his actual screen etc. Are you seeking to lock down all possible means of transmission? Most? Some?

I will assume you want to go with plausible technology. If you are aiming at futuristic, then we all get a lot more lattitude but my impression is you want current day plausible. I am going to extend the polymorphic virus idea. I am minded of many online banking schemes, the ones where you get a key fob which generates a onetime code for login, so user name password and the onetime code generated by the fob are requisite for access to be granted. What if the putative fob was GPS enabled and implanted under the protagonists skin for extra ick factor, and set off an alarm if removed more that a meter from the protagonist. maybe it doesn't even work if not operated within the ebil gubbmint facility. Maybe there is a carrier signal like wifi required for the thing to even be operational, a carrier signal only found in the ebil gubmint facilities. Maybe a subplot might be the search for the means to crack/replicate that signal.

ETA: Now that I wrote that, that's all scarily doable.

 

[Charlie Wilkes]

Let's say one or more people are keeping information of an incriminating nature on a particular computer. Another individual, thinking to blackmail them, copies all the files off the computer. However, when the people to whom he gives them try & read the files, they're too messed up to be deciphered. Something along those lines...

Please be gentle. I have limited understanding of computereze! I'm just trying to suggest enough info to make it believable, I don't need to go into a lot of detail. Just so someone who's reading it won't go, "Oh, that wouldn't work!" and ruin their suspension of disbelief.

Thanks for the answers so far!

Hmmm. You could introduce some kind of viewer software that decrypts individual files, but the blackmailer doesn't realize it is required.

Amazon actually has a media player that does this. I have some movies that I have bought and downloaded from Amazon. They show up in a file manager as ordinary .wmv files, and they can be copied, but they will only play on Amazon's player. I would guess my copy of the Amazon player is keyed to my account, too, and my movies would not play on the same software keyed to a different user. But I have never tried that so I'm not sure.

I suppose a programmer could add this capability to any open-source software, like VLC for media files.

 

[Brian-M]

So what you need is a program that silently (the term used in the computer industry is "transparently") corrupts/encrypts the data as it's being written to a removable device, such as a USB thumb drive, a streaming tape drive, over a network, or (if you're old enough to remember them) a floppy diskette. The important thing here is the files get encrypted any time they're not being written to the local hard drive.

Or you have a transparent program that decrypts an encrypted file when an approved application attempts to read from it, so the data the approved application "sees" is not encrypted. But when a non-approved application tries to read the file (such as file manager, when it tries to make a copy), the transparent program does nothing, and the application reads/copies the encrypted version of the data.

ETA:

Or maybe it's something like a Password Protected PDF or DOC file, and...

• The would-be blackmailer doesn't realize that the computer is set up to automatically fill out the password .
• The password was typed in and the PDF or DOC was left open on the computer while the owner went to get a cup of coffee, which is when the blackmailer snuck in and made a copy.
• The blackmailer sees the owner working on the file, and sneaks back later to make a copy without opening it first, so doesn't realize that it's password protected.

So when he tries to open up the copy of the PDF or DOC, instead of incriminating evidence he gets a request for a password.

 

[Blue Mountain]

Or maybe it's something like a Password Protected PDF or DOC file, and...

• The would-be blackmailer doesn't realize that the computer is set up to automatically fill out the password .
• The password was typed in and the PDF or DOC was left open on the computer while the owner went to get a cup of coffee, which is when the blackmailer snuck in and made a copy.
• The blackmailer sees the owner working on the file, and sneaks back later to make a copy without opening it first, so doesn't realize that it's password protected.

So when he tries to open up the copy of the PDF or DOC, instead of incriminating evidence he gets a request for a password.

I know Microsoft Word can write encrypted documents, and attempting to open them causes a password dialogue to appear.

 

[abaddon]

I know Microsoft Word can write encrypted documents, and attempting to open them causes a password dialogue to appear.

Even in the worst case scenario where our blackmailer does not know the password and simply happens upon said document open on an unattended PC, the sequence Ctrl-A, Ctrl-C, Ctrl-N, Ctrl-V, Ctrl-S, fill in file name and location gets a new unpassworded full copy in five keystrokes plus whatever name you chose for the copy. I think he is after something more subtle for whatever his opus is.

 

[geni]

Let's say one or more people are keeping information of an incriminating nature on a particular computer. Another individual, thinking to blackmail them, copies all the files off the computer.

Why? Is the hard drive nailed down?

However, when the people to whom he gives them try & read the files, they're too messed up to be deciphered. Something along those lines...

At the present time no one has managed to show if this is possible or not in theory (other than onetime pad setups) however no one has managed it in practice.

Please be gentle. I have limited understanding of computereze! I'm just trying to suggest enough info to make it believable, I don't need to go into a lot of detail. Just so someone who's reading it won't go, "Oh, that wouldn't work!" and ruin their suspension of disbelief.

Give up. Now.

Seriously the computer security and encryption nerds operate on a level so far beyond anything you understand (I'm assuming you don't have a maths Phd) that the odds of you describing something they can't find a flaw in are pretty much nill.

 

[Charlie Wilkes]

Why? Is the hard drive nailed down?



At the present time no one has managed to show if this is possible or not in theory (other than onetime pad setups) however no one has managed it in practice.




Give up. Now.

Seriously the computer security and encryption nerds operate on a level so far beyond anything you understand (I'm assuming you don't have a maths Phd) that the odds of you describing something they can't find a flaw in are pretty much nill.

It could make for an interesting story. I think the OP should consult some of these encryption nerds, but I wonder if they would say it's an insoluble problem.