Is it possible to further encrypt an EPUB document by password

[TES]

Hi - I am wondering whether anyone might know whether it is possible to further encrypt EPUB documents by a numeric password code? That is, in addition to the encryption that is possible under Adobe, can you then add a second protective layer by specifying a unique 4 digit code that enables you to open up the document? Thanks for your help.

[DiapDealer]

It's just a zip file. You've been able to password protect zip files since time began. But if you're looking for ways to guarantee that no one will ever be able to read the document, you're working way too hard. There's much easier methods.

[KevinH]

Hi,

You can encrypt any file any way you want but ...

- no standard ereader on the market would be able to read it
- a 4-digit passcode can be easily broken by brute force
- for anyone to read that file without brute force breaking the encryption, you would have to store that passcode someplace and that info can be found and read from your system

Basically what you are adding is worthless just as most DRM systems today. They do not protect the ebook from being copied by anyone who owns a copy of that ebook and wants to remove the DRM or by people who want to pirate the ebook. They just lock unwary users into one device or platform. So all they do is protect the ebook store and not the author.

[TES]

Thanks - so I guess that it is pretty pointless having a second encryption layer as it can be easily broken.

[speakingtohe]

If you can make it someone can break it

[taustin]

Originally Posted by speakingtohe

If you can make it someone can break it

Oh, unbreakable encryption is easy. So long as you don't need to decrypt it yourself. It's called a "random number generator." It works best on write-only memory, of course.

[QuantumIguana]

Even if there was a password that was uncrackable, it wouldn't protect the book as long as human eyes could read the screen. A script could turn the page, and take a screenshot. It would then be a simple matter to OCR the screenshots.

[AndrewH]

Originally Posted by TES

That is, in addition to the encryption that is possible under Adobe, can you then add a second protective layer by specifying a unique 4 digit code that enables you to open up the document?

Who are you trying to "protect" the files from? If you're trying to keep roommates or family members from reading files on your computer there are much more effective ways of doing so. If you're trying to keep pirates from pirating... well, good luck with that.

[bill_mchale]

Originally Posted by TES

Thanks - so I guess that it is pretty pointless having a second encryption layer as it can be easily broken.

Well, I guess that depends. What is the point of the second level of encryption? Yes a 4 digit key is not likely to be very secure, but lets say you are living in an oppressive third world country and are afraid the government will hack into your computer and arrest you for the books you are reading. There are plenty of file encryption programs out there that provide fairly strong encryption. No ebook readers support them, so you would have to manually decrypt before use, but while encrypted, only you would be able to get access to them...

--
Bill

[QuantumIguana]

If an oppressive government hacks into your computer, they can probably decrypt your files. It would probably be more productive to keep them out of your computer in the first place, or to store your books off of the computer.

[ApK]

Originally Posted by taustin

Oh, unbreakable encryption is easy. So long as you don't need to decrypt it yourself. It's called a "random number generator." It works best on write-only memory, of course.

Remember the purported "Image" recursive encryption system that would let you back up a 1GB hard drive to a single 3.25" floppy? It did it. It eventually reduced everything to all zeros...

(I suppose, if pressed, the 'inventor' could have claimed "That's correct...it just so happens that the decryption key is 1GB long....and coincidentally looks a lot like your original data....")

[CJJ]

Is it just me or is thread getting funnier and funnier.

[Penforhire]

Your files are only really safe using programs like TrueCrypt or PGP while the encrypted file is not "mounted." There are ways to get the password when the system is "live." Example legit hacking program here -- http://www.net-security.org/secworld.php?id=9077 . However, we're still safe while our files are not mounted.

When is this a high risk? When you use sleep mode rather than fully powering off.

Also if someone has access to your physical computer you might as well bend over now (for example, installing a keyboard logger or just a hidden camera looking over your shoulder).

[ApK]

Originally Posted by Penforhire

Also if someone has access to your physical computer you might as well bend over now (for example, installing a keyboard logger or just a hidden camera looking over your shoulder).

So true. Note Law #3:
http://technet.microsoft.com/en-us/l.../cc722487.aspx

[bill_mchale]

Originally Posted by QuantumIguana

If an oppressive government hacks into your computer, they can probably decrypt your files. It would probably be more productive to keep them out of your computer in the first place, or to store your books off of the computer.

I am not so sure. Even today some public key crypto-systems appear to remain unbreakable with large enough keys. Granted the NSA might have figured something out, but then again, they may not have.

--
Bill