Linux Encryption HOWTO 60
lazyecho writes: "How to set up a Linux 2.2 system to use encryption in both disk and network accesses. This document describes how you can use the International Kernel Patch and other packages to make hard disk contents and network traffic inaccessible to others by encrypting them." Hey, your box is stable, why not mix it up a bit? I'm not a security nut, but this strikes me as a fun one anyway.
Re:Never gonna be as good as thermite. - Silly! (Score:1)
Don't need to eliminate 100% of the disk... just a well selected 1% will do...
Re:Crypto Progs (Score:1)
Scramdisk is a very good program for windows (although it has one of the ugliest user interfaces I have seen), but it serves essentially the same purpose as using an encrypted loopback device.
Scramdisk will be a welcome addition to linux (though hopefully they will pretty it up a bit), especially if they make it easier for novices to use encrypted filesystems. It also has the ability to use steganography like StegFS, which is as added bonus.
better information (Score:1)
That HOWTO is good, but severely out of date. To quote Cha pte r 10 - Encrypting files and drives in Linux, BSD, and other Unices" [securityportal.com]
Chapter 10 - Encrypting files and drives in Linux, BSD, and other UnicesBy: Kurt Seifried, seifried@securityportal.com [mailto], for http://www.securityportal.com/ [securityportal.com]
; OverviewDo you have files on your computer that you wouldn't want your spouse to read, or perhaps your main competitor. Chances are if you use your computer for work or general usage the answer is yes. Also what happens if you want to send a file to someone, or let them download it from you, but you only have access to a public site (like a free web hosting company). The answer is to encrypt the file, and fire it off. For UNIX you have several choices, PGP, and GnuPG, as well as Guardbot for web based file transfers. If you work with files that are sensitive (such as spreadsheets containing sensitive financial data) the constant hassle of encrypting and decrypting the file (as well as the fact a decrypted copy will be stored on the filesystem, leaving a window of opportunity for an attacker) can get tedious. If this is the case you will want to use software such as, BestCrypt (commercially licensed but free for Linux with source code), or PPDD (Private and Top Secret, GPL licensed) which are both very similar in execution and general usage.
Encrypting files and drives PGPPretty Good Privacy is available as a command line driven program for most UNIX platforms, and there are a variety of front end GUI programs for it. I would not recommend using PGP on a UNIX platform since a completely OpenSource, and compatible replacement is now available, in the form of GnuPG.
GnuPGGnuPG is a GPL licensed (a.k.a. completely free in every respect), written in Germany (a very pro-crypto and pro-privacy country). Since it is available in full source code chances are it has been ported to your UNIX platform (and if not try compiling it, it might work). You can download GnuPG [slashdot.org] as a compressed tarball of source code, and there are links to a number of source and binary packages for various UNIX platforms. Once installed GnuPG behaves very similarly to PGP. The first thing you'll probably want to do is generate a new keypair, simply use the command "gpg --gen-key", it will create a ".gnupg" directory in which to store your keys, option files and so on and exit, you then run it again and it will lead you through the key creation process. Choosing the defaults during key generation is a pretty safe bet, although you may want to use a 2048 bit keysize (realistically if someone manages to crack 1024 bit keys, chances are they can get at your 2048 bit key, however if they are only trying to brute force it a longer key is a good way to reduce the chances of that). For personal keys the expiry is typically set to "0" (that is to say they do not expire), however if these keys are for corporate use, or for really sensitive information it is a good idea to expire keys and rotate them (every month, year, decade, whatever your security policy dictates). The most important thing when generating a key (in my opinion) is the passphrase. This is a string of characters which should consist of letters (upper and lower case) numbers and punctuation marks, the longer the better (I'd say the bare minimum is 10 characters). This controls access to the private key, which is used to sign items (and if compromised means an attacker could easily impersonate you), and to decrypt data (meaning an attacker could access all your data). Keep your private key secure! If an attacker gains access to this key they only have to brute force the passphrase, which is typically a lot weaker then a random 1024 bit (or longer) key. Worse yet they may steal your passphrase, with a keyboard sniffer or similar attack, resulting in a compromise of your key. If the attacker does not have access to your private key they will be forced to guess it, which takes a brutally long time (on average however, there is a chance they may guess the key correctly on their first try).
Signing files is useful if you want to distribute a file to someone, and be able to prove that you sent it, and it was not tampered with. Internally GnuPG takes a hash sum (such as MD5 or SHA1) of the file (basically it reduces the file to a shorter, unique string of data) which it then encrypts with your private key, generating a signature. This signature can then be decrypted with your public key, resulting in possession of the hash sum of the file, simply take the hash sum of the file in question, and if the they match, then obviously the file is what it claims to be. This signature file can be a binary file, or converted into text (for example signing email, or distributing file signatures via email). To sign a file with gpg simply use :
$ gpg -b filewhich will create a detached signature of the file.
To verify the signature use "gpg --verify file.sig file". If all is well you should see something like:
$ gpg --verify file.sig file gpg: Signature made Sat 15 Jan 2000 05:23:31 AM MST using DSA key ID 47D0D9A8 gpg: Good signature from "Kurt Seifried <seifried@securityportal.com>"If someone has fiddled with the file or signature you will see something like:
$ gpg --verify file.sig file gpg: Signature made Sat 15 Jan 2000 05:23:31 AM MST using DSA key ID 47D0D9A8 gpg: BAD signature from "Kurt Seifried <seifried@securityportal.com>"Encrypting files is also relatively simple, a person uses your public key to run the data through a one way algorithm which results in a seemingly random mishmash of data, you can then use your private key to recover what the original data was, thus decrypting it. To encrypt a file to someone you first need their public key, you can download it from their homepage (if they have it online of course), or you can go to a public key server, of which there are many:
http://pgp.ai.mit.edu/ [mit.edu] - PGP key server
http://www.keyserver.net/ [keyserver.net] - OpenPGP key server
Once you have their key it is simply a matter of signing and encrypting the file (just encrypting the file is rare as there is no proof of who the data is from, unless you use some other method, like physically handing them a floppy disk with the encrypted file). The following is an example of me signing a file and encrypting it with my public key:
$ gpg -s -e file You need a passphrase to unlock the secret key for user: "Kurt Seifried <seifried@securityportal.com>" 1024-bit DSA key, ID 47D0D9A8, created 2000-01-15 You did not specify a user ID. (you may use "-r") Enter the user ID: seifried@securityportal.comThe user ID can either be the key ID (such as: 47D0D9A8), the email address associated with the key (seifried@securityportal.com [mailto])or the name (not recommended as these are not unique, there are many John Smith's). You will end up with a "file.gpg" that is binary, if you wish to send the file via email it is advisable to use the "-a" ("--armor") option which will result in "file.asc" and is ASCII text, so you can read it straight into an email, or print it out, mail it, and let them OCR and decrypt it at their end. To decrypt a file sent to you simply:
$ gpg --decrypt file.asc You need a passphrase to unlock the secret key for user: "Kurt Seifried <seifried@securityportal.com>" 1024-bit ELG-E key, ID 47D0D9A8, created 2000-01-15 (main key ID 39B0D9A8)and it will display the file (hopefully a text file) to your screen, followed by the veracity of the signature (if you have the persons public key):
gpg: Signature made Sat 15 Jan 2000 06:06:19 AM MST using DSA key ID 47D0D9A8 gpg: Good signature from "Kurt Seifried <seifried@securityportal.com>"if you want to save the decrypted file simply use "--output filename" and it will dump the content to "filename". You can also use shell commands such as "|" or ">" to further mangle the output (this is useful if you have automated systems such as a reporting mechanism which sends encrypted emails to a central repository).
BestCrypt
BestCrypt is a disk encryption program available for Windows and Linux. The nice thing is you can create an encrypted container (a file that is then mounted as a filesystem), and use it in Windows or in Linux (as long as it resides on a partition accessible to both, so putting it on your Windows partition is fine since Linux reads almost all Windows partition types). BestCrypt consists of some kernel modules (so your kernel will need to support loadable kernel modules obviously, and it helps if you are using tools like depmod, modprobe and the kernel module loader), and a userspace utility called "bctool". This program is however officially in "beta testing" for Linux, and probably should not be used for critical data (if it is, make sure you have backups). After testing BestCrypt for Linux I am satisfied that even though the software is officially beta, it is probably stable enough for most users, however your mileage may vary, all sales final, and don't blame me for any lost data. The only real problem with BestCrypt is a severe lack of documentation, while there is a man page that explains basic options, there is not a single example of how to create and mount a container (I suspect the release will have documentation, their Windows version documentation is quite good, a half meg helpfile). You need to download the software first, available as a source tarball, and source rpm (very easy to install on an RPM based system). Simply download either one, I would recommend the source rpm if you can.
# rpm -Uvh BestCrypt-0.3b-1.src.rpm BestCrypt #################################################followed by a lot of text while it unpacks, compiles and assembles the source RPM and binary RPM. You should then have a:
Simply install the binary RPM with a:
#rpm -UvhIf you do not have an RPM based system, or the source RPM doesn't work for you, compiling the source code directly from it's tarball should be possible. Simply download the file, unpack it to an appropriate place (such as /usr/local/src) and issue the
commands:
#make #make installAnd you should be up and running. The first step is to create a container (a file that is encrypted and mounted as a partition):
# bctool new -a blowfish -s 10M file Enter password: Verify password:You can of course use the "gost" or "des" algorithms, I would not recommend them as gost is less tested then the "twofish" and "blowfish" algorithms that BestCrypt supports, and single des is to easy to brute force. The next step is to format the container, you'll probably want to use msdos if sharing with Windows (i.e. a dualboot Linux and Windows machine), or if just Linux then ext2 is a good bet. You can also specify the size, if you make it so small this can be a problem, but because it is a file and not a true partition you can easily create a new, larger file, move all the data to it and use it instead of the older smaller one.
# bctool format -t ext2 file Enter password: mke2fs 1.15, 18-Jul-1999 for EXT2 FS 0.5b, 95/08/09 Filesystem label= OS type: Linux Block size=1024 (log=0) Fragment size=1024 (log=0) 2560 inodes, 10238 blocks 511 blocks (4.99%) reserved for the super user First data block=1 2 block groups 8192 blocks per group, 8192 fragments per group 1280 inodes per group Superblock backups stored on blocks: 8193 Writing inode tables: done Writing superblocks and filesystem accounting information: doneOnce the file is formatted you should be able to mount it:
# bctool mount fileAs you can see it is mounted as a part of the filesystem, just like a floppy disk would be for example. Remember to control access to the directory hosting the encrypted files carefully, no matter how good the encryption, if you have it set world readable you won't have gained any security. Also remember that as a user, root owns the / and can take ownership of any file or directory and see what's in it. Alternatively if an attacker gains root access they can log your keystrokes (or terminal traffic) and gain your password (and access to your files). As always your security is only as good as the weakest link.
PPDDPPDD [slashdot.org] is similar to BestCrypt, but instead of creating a file, encrypting that and mounting it, it actually uses a partition which is encrypted and mounted using the PPDD driver, because of this it can do a few additional things BestCrypt can't. If you only want to encrypt a few directories then I advise compiling PPDD as a kernel module, but if you want to encrypt the entire file system (including what you boot from) you will need to compile PPDD directly into the kernel (although as of 1.0 it's not to hard). Unless you have a GPL only policy I would recommend using BestCrypt if you are new to this (it is easier to install and use, and you can buy support). PPDD does have one enormous advantage over BestCrypt however, you can encrypt all of the system, including the boot drive and swap partition, making it ideal for situations such as laptops with sensitive data and minimizing the risk (to zero if need be) of accidentally leaving sensitive data in an unencrypted location (such as the swap file, /tmp, and so on) so if you need
a higher security level I would recommend PPDD over BestCrypt
(simply because you can encrypt everything). Another advantage of
PPDD is that is uses two passwords instead of just one for each
encrypted filesystem, so you can give one administrator one
password, and another administrator the other password, meaning
no single person can gain access to the data. Unfortunately as of
the writing of this chapter PPDD is not available for kernel
2.2.13 or 2.2.14, so you will have to run the older 2.2.12 kernel
(which is the stock kernel on many distributions in any case).
Download PPDD, and unpack it in a suitable location, such as /usr/local/src/, there are several files you should read, most
notable the README file, and once done install I would recommend
reading the PPDDHow.txt file. Installation is rather simply with:
#make check_linux #make trial_patch #make apply_patch #make devicesThis will first test the kernel source to make sure it's the right version and so on, then it will test the patches, then apply the patches proper, and then create the devices needed (similar to what BestCrypt does). At this point you need to recompile your kernel, first make sure you go into the configuration (via make config or make menuconfig or make xconfig), and enable the PPDD driver (in the Block devices section). Then save the config file and recompile the kernel as your normally would. Once that is done you will have to install the new kernel (copy it to /boot typically, edit lilo.conf and
rerun lilo). Once you have rebooted you will want to build the
tools for PPDD and install them with:
#make #make installAt this point you should be ready to use it, however I would recommend running the tests with:
#make testThey take a while to run, but it will save frustration later on if something is broken. Using PPDD is relatively simple, there are a number of utilities for creating, managing, encrypting file systems, and so on. You will also want to set the permissions and ownership on the /dev/xxxx that contains your encrypted data so
that only root has access to it, PPDD will complain otherwise
#chown root:rootAt this point you should have a directory called /crypt which
is /dev/hda3 (although on df and the like it will show up as /dev/ppddx). I will cover how to encrypt you entire filesystem
with PPDD, at a later date however (it is extensively documented
though).
GuardbotAnother new possibility is Guardbot [slashdot.org], which password protects www pages. Essentially there are two components, an applet that encrypts the data, using DES (56 bit keyspace), and an applet that will decrypt the data with the password you provide. The advantage of this over traditional server based methods of control (such as htaccess in Apache) is that the user manages it fully, and can protect each file individually without much setup. To fully take advantage of the keyspace available your password must contain upper and lower case letters, numbers (and punctuation marks, but this can confuse users) of around 10 letters, however since people tend to choose less then random passwords a longer password then this is advisable. This program would be useful for getting files to other people cheaply (simply sign up for some free web space, post the file up, and get the password to the other person securely).
Hiding files and data on your computerIt is no longer enough in some countries to encrypt your data to prevent access to it. Recently in Britain a law was created making it a criminal offence to refuse to give up encryption keys or plain text versions of encrypted data.
StegHideStegHide hides data in files such as sound and picture files where not all of the bits in a byte are used. Since the data is encrypted it will appear random, and proving that the data is actually there is difficult. The only downside is to store a one megabyte file you need a sound/picture file of several megabytes, which can be cumbersome (but hard drives and high speed access are becoming cheap so it's a moot point). You can get StegHide at: http://www.stego.com/ [stego.com].
StegFSSteganographic File System actually hides data on your harddrive, making it difficult to prove that it even exists. This can be very useful as the attacker first has to find the data, let alone break the strong encryption used to protect it. You can get StegFS from: http://ban.joh.cam.ac.uk/~adm36/StegFS/& lt;/a> . [cam.ac.uk]
OutGuessOutGuess hides data in image files, meaning you can send files in a way that won't attract to much attention (and can't really be prooved either). You can get it from: http://www.outguess.org/ [outguess.org].
Does the 5th protect me from divulging passwords? (Score:1)
Re:Never gonna be as good as thermite. - Silly! (Score:1)
Very useful law survey cited in HOWTO (Score:2)
Re:nice.. but remember the rest.. (Score:2)
That's not the point. I'm looking into filesystem crypto for my laptop, not for fear of them (insert your favorite governmental boogeyman here) but because the thing holds my private key, access info for a bunch of remote systems, private information, email that can be potentially sensitive for my clients, etc.
So if I loose the thing, I don't want that data to be accessible to whoever stumbles upon it.
Now for encrypting your home box, unless you live with the hacker from outer space or work for Echelon, there isn't much point...
Re:Crypto Progs (Score:1)
boxes inside boxes. (Score:1)
Yes, everyone is innocent until proven guilty. That's why search warrents should only be given out for good cause even though this helps criminals hide. The key word is reasonable. The protection is more than one branch deciding what reasonable is and a public proof that can be questioned. Once convicted, however, you have no rights. You will be fined, imprisoned or even killed, oh my.
In any case my main point was that the use of encryption to hide criminal activity is not something we should be happy about or advocate anymore than we advocate criminal activity.
Re:Never gonna be as good as thermite. - Silly! (Score:1)
Oh, that must be why my hard disks keep filling up. The write head is unable to overwrite the contents of a sector, so instead it has to find one that has never been used before.
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Re:What I think I'd like to see... (Score:2)
Actually, the message is encrypted with a session key, and the session key and a message hash is encrypted to a public key and tacked onto the message.. You can tack as many encrypted session keys and hashes to the message as you want, they aren't big at all... The bulk of the message is encrypted with a single session key.
Re:nice demonstration of downside (Score:2)
Where, you might ask?
Well, if I was growing MJ, and wanting to dump the heat in the least expensive, but most innocent looking way, I would build myself a large swimming pool, preferably with one end for diving (>10 feet deep). After digging the hole (but prior to the cement pouring), I would lay copper tubing coils all over the bottom, bringing the taps up near the pumps. I would set up an extra pump, and a heat exchanger to wherever my growing area was at, insulate the hell out of everything (to make sure heat doesn't escape through the walls or ceiling), install some nice air circulators to circulate the air through the heat exchanger, then pump a brine/antifreeze mixture through the whole thing. I might even go so far as to build a "spa" to monitor ambient vs. cooling pond (for that is what the pool would be) temperatures.
Heh, who'd of thought there would be a need to put a heatsink on your MJ growing op?
I support the EFF [eff.org] - do you?
interesting (Score:1)
CmdrTaco officially insane (Score:2)
QOTD:
Hey, your box is stable, why not mix it up a bit?
HAHAHA! Famous last words, Taco!!
Sometimes that can be a disadvantage. (Score:2)
"But Boris, that *was* the real, final key! I swear there aren't any other keys for that drive, I swear!"
You can't have it both ways...
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Re:nice demonstration of downside (Score:2)
I'm just mentioning this because it's amazing how many technological innovations become the tools used to invade privacy. I mean, if it's okay for them to point an infrared sensor at your roof, is it okay for them to point a laser interferometer at your window to see if anyone inside is talking about drugs? It's non-invasive, right? They didn't actually enter your premises, right?
All this ties in so well with the EU/US anti-privacy treaty [slashdot.org] in the works.
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Re:StegFS sounds awesome... But... (Score:3)
An oversimplified example would be that if you hide information in an (uncompressed) .wav file, you store information A to the lowest bit of the left channel and information B to the lowest bit of the right channel.
For this kind of operation you should propably choose a big file with plenty of 'insignificant' bits to choose (like MPEG video) so it would be easy to explain why you didn't use every possible bit to store data.
Re:RIP-- bad for your health. (Score:1)
They'll crack it so fast it'll make your head spin (Score:1)
Re: (Score:1)
Great for Laptops / Handhelds (Score:5)
Now, IAMAL[?] [everything2.com], but here is how I got it explained to me: Items on your person fall under the dictates of law governing search and siezure. If you have a cabinet in your home, the police are allowed to search is if they have probable cause; but if you have a safe in you your home, you are not required to volunteer the combination to it without a subpeona. Goes the same for passwords and crypto, too, AFAIK. They can put me in the squad car, but until they get a court order, I don't have to tell them the password to my PDA or my GPG/PGP secret key passphrase.
This is a good thing, because an over-zealous officer could start dinking around on you laptop and find some incrimitation evidence (violating S&C Law), but tell the judge that he found 'by accident'. Who is the judge going to believe? But if you have it all locked up tight, nothing short of a circuit court judge can force you to unlock it.
And please not my gratuitous use of the phrase 'over-zealous'. The VAST majority of law officers are decent human beings - its just those choice few emmy-award winners that makes everyones life hell.
At the very least put a pasword on your PDA, laptop, and modified-laptop-car-MP3-Player. Especially the MP3 player -- Ms. Spears would be so pissed if she found out I downloaded all 50 remixes of "I'm a closet dyke" off Napster
Re:Great for Laptops / Handhelds (Score:1)
While that kind of thing can be overturned on appeal, by that point it may be too late, especially reputation-wise. A simple, but not always easy to follow rule is "Never put anything on the laptop (or PDA) that you're not ready to have read by anyone." If it means that you have to store your secure files or porn pics somewhere else, so be it, but PDAs and laptops are a lot more accessible and much more easily stolen.
Kierthos
Crypto Progs (Score:3)
The Ultimate in Hard Drive Encryption (Score:3)
Masquerading as a set of utilities for mounting an ext2 partition from MS-DOS, Ltools [fht-esslingen.de] is guaranteed to make your linux filesystems completely inaccessible to anybody.
One of the most glaring insecurities in most disk encryption systems is the user themselves. They may simply be threatened with hot lubricating jelly and will reveal the all important encryption keys. Not so with Ltools - even the user is unable to retrieve the information once it is encrypted.
Simply install the Ltools package on your windows partition and then type 'lmkdir etc'. I did this yesterday and believe me, there's no way anybody's accessing my root filesystem!
Pr0n (Score:1)
windoze: Error reading drive. Format? yes no
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If my facts are wrong then tell me. I don't mind.
Re:Well, Obviously . . . (Score:1)
Re:Not as good as you think. (Score:1)
- Steeltoe
Re:The Ultimate in Hard Drive Encryption (Score:1)
De-crypt/delete option (Score:2)
RIP: Aptly Named. BOYCOTT BRITAIN! (Score:1)
- If you don't hand over your private keys, you face two years in jail.
- If you tell anyone about the insident, you go to jail for FIVE years.
- ISP's are responsible for buying the gear to perform the monitoring.
- And ALL net traffic either coming from or going to a British site go through MI-5. (That's like the NSA with FBI-like police powers for an American analogy.)
So, for example, if I worked as a sysadmin for a company with encrypted hard drives, and MI-5 drops by and demands the hard drives be opened, and I say, "I can't do that. The information on our encrypted systems are classified.", I get to go to a British jail for 24 months. If I have the audacity to report the incident to the CTO (or whoever is in charge of our IT), I could go to jail for 5 years, and be so far behind the SOTA (State Of The Art) I would need at least a year to recover to be employable! So, I say that we push to screw Britain for screwing us.RIP-- bad for your health. (Score:1)
Re:What I think I'd like to see... (Score:2)
The other is that for many public-key systems (if not all?), you'd need one version of each file for *every* private key meant to decrypt it, which in some settings might be a bit much if one runs into problems assigning groups.
Root could easily be given access under such a system by always having one copy encrypted using the root key, or alternately, key escrow, if it were critical that root have such (Not necessarily, say, for an ISP admin, but perhaps for a system with classified material...).
nice demonstration of downside (Score:1)
I'm going to believe the officer. You got caught with evidence of criminal activity in plain sight, and I'd be glad.
Unreasonable search and seizure laws are designed to protect people against government meddling and other abuses. As a side effect, criminal investigations can be more difficult. You forfeit those rights, however, when you engage in criminal activity also known as violating the rights of others for your own benefit. Once a good reason to search you is publicly established, you will be searched and there is nothing unreasonable about it. I hope the police crack your PDA, just like detectives used to figure out the secret code in a pimp's little black book.
That encryption might shield criminals is a downside that we will all just have to live with. It's not something that should be celebrated.
This whole thread is off topic.
Re:De-crypt/delete option (Score:1)
Couldn't they just image the disk first?
The other is that they'd probably *ask* you for the passphrase and record it. Why should, say, Feds, let you use the computer (and if they DID, they're well aware of things like TEMPEST ELINT and whatnot)? They'd do the study of it...
Then they nail you for destruction of evidence / obstruction of justice, make another copy, and ask again. You'd have the option of increasing your sentence as much as you like.
Re:De-crypt/delete option (Score:2)
If you do it properly they won't be able to prove there's any other data there. There's not much to tell them it's 32x chaff instead of 64x chaff.
Re:CFS (Score:1)
It's nice too to be able to burn a CD of the encrypted files, along with a plain-text directory containing the crypto software, and not have to worry about who finds it.
Re:To take this inverse (Score:1)
Re:No need thanks to the DMCA (Score:1)
Cryptonomicon, anyone? (Score:1)
.siglost
From experience... (Score:1)
Re:What I think I'd like to see... (Score:2)
This isn't how public-key crypto is usually done, and nor is it at all how Leknor suggested it. You generate a random key with which you encrypt the file. One key for the file! Then you take that key and encrypt it with the public key of the file's owner and the file's group (each group would have a public/private key pair). For each group on the system, you encrypt the group's private key in each of its member's public keys.
Then, when a user logs in, s/he can decrypt the decryption keys for files s/he owns, and the private keys for the his/her groups. With the group private keys, s/he can decrypt the decryption keys for files that s/he has group access to.
So the overhead is in storing a public key for every user and group, the private key for each group encrypted with the public key of each of its members, and for each file, two copies of the decryption key for that file, one encrypted in the owner's public key, one in the group's public key.
So you lose a couple kb per file, and (very generously) a meg for the user/group database if you have a system with several users. A system like sourceforge which has zillions of users would have several megs of overhead, but such a large system isn't likely to notice that with it's many many gigs of disk space.
-Matt
Useful for /home/ME (Score:2)
Never gonna be as good as thermite. (Score:3)
Nope - never gonna feel truly safe until I got a big block of thermite tied to my hard drive and the dead-mans trigger in my left hand. :)
Win32 Napster Client. [geocities.com]
WOW! (Score:4)
1 year later:
Why god do i have to encrypt everything? WHY!?
I remember when it all started. It started with the disks, then i lost my job, then i lost my girlfriend, and i lost what life i had.
DAMN YOU Linux Encryption HOWTO! DAMN YOU STRAIT TO HELL!!!
No need thanks to the DMCA (Score:2)
Re:WOW! (Score:1)
I couldn't have said it better...
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pb Reply or e-mail; don't vaguely moderate [ncsu.edu].
"this strikes me as a fun one anyway" (Score:1)
__
Data Integrity (Score:4)
What if my filesystem were to go down? I could never recover my data. In addition performance would be hindered severly by the blocking overhead of the encryption and decryption (which is essentially the same exponential operation backwards and forwards).
Until someone develops a hardware solution, I have to say, "no thank you."
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In the FreeBSD ports directory (Score:2)
ftp://research.att.com/dist/mab/cfs.ps
and I think they have also built a kernel module to do it at the kernel level (cfs looks like an NFS file mount, to get around all that nast kernal stuff), but I don't have the time to go hunting for it...
Yet another 'feature' that is Brand New(tm) now that Slashdot has 'discovered' it.
StegFS sounds awesome... (Score:4)
You know it's hard core when the docs refer vaguely to the ability to keep data secret in the face of torture. 1024-bit public-key encryption is all well and good, but threaten me with a glass rod, and I'll hand that key right over. Plausible deniability is where it's at!
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Re:In the FreeBSD ports directory (Score:2)
Also check out TCFS http://tcfs.dia.unisa.it/group-sharing.html
nice.. but remember the rest.. (Score:1)
encrypting everything is useful.. but remember anyone can gain access to your machine with a large caliber handgun and easy access to your head.
Still fun enough to give it a look though...
What I think I'd like to see... (Score:3)
Each file is encrypted with a key that is then encrypted with the public keys for the user and group and maybe unencrypted if everybody has privilages.
Then when a user logs in his private key is decrypted and the private keys for the groups he belongs to is decrypted with his private user key.
Then with all the private keys the user can decrypt the keys that decrypt the files.
I'm sure there are holes in this, so please tell me. All I know is what i've learned from reading about PGP, SSH, and CSS (hope I don't get sued for learning) and that isn't much. The only drawback I see is maybe a file could be out of the reach of root, but that isn't a drawback IMO.
Leknor
Perfect (Score:1)
Re:Data Integrity - Agreed (Score:1)
To take this inverse (Score:3)
Yeah sure it's secure but the disk isn't encrypted and I'm really lucky to have a boss who knows Unix.
Oh and I keep a Linux CD handy in case I need to restore my computer from a nasty crash.. how smart of me...
Apparently my Boss dosn't share my intrests in techno advocacy.. the DVD DeCSS directory means.. I'm out of work...
Oh well...
So I get home.. my girl friend isn't quite so tech savy as I am but I'm allways teaching her stuff...
Hay she learned a new trick on her own today..
I mean now that I'm out of work my computers at home.. so she started tinkering around..
I never did give her much access so she picks up the cd..
the dam porn directory...
Now I have no girlfriend...
Mom wants to use the computer.. she's pritty tech savy... learnned CP/M way back and had access to a PDP11/70 when I was still a kid...
But sadly all her equipment is obsolete... Commodore Pets.. Apple IIs.. She wants to use my Linux box while I'm out looking for work...
Thats ok.... hmmmm
Encryption HowTo... yeah Mom would he happy to have her network connection encrypted.. (I'll just encrypt all my personal files while I'm at it)
Please note.. the above is fiction.. my boss dosn't look at my computer and I can't get my GF to even consider Linux...
I don't have a porn directory and I keep DVD DeCSS on a ZipDisk...
Re:Data Integrity (Score:4)
1: The encryption works at a different level from the filesystem. If the filesystem gets corrupted, you can still decrypt the data, and you will be in the same position you would be if you didn't use encryption at all. Of course if you forget your password you'll never get the data back, but thats the point.
2: And the blocking overhead? All the algorithms in the patch have 64 or 128 bit block size. This is far less than the size of a disk block, so i wouldn't be worried.
3: There is no exponential operation. You are thinking of RSA, which is a public key algorithm. Public key algorithms have longer blocks and are slower than private key ones. They are necessary when you want anyone to be able to encrypt, but only you to be able to decrypt. Seeing you don't need this for disk encryption, private key algorithms are more appropriate.
4: There are many hardware solutions, but they are generally designed for network encryption. Presumably you could write drivers to get them to do the computation for the disk encryption. Anyway, the processing isn't the main thing killing performance: twofish runs in 17 cycles per byte. The performace killer is that it works through a loopback device, which makes readahead and caching less efficient (i think thats the problem, but i'm not entirely sure about this).
Re:Never gonna be as good as thermite. (Score:1)
Local Disk encryption (Score:2)
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Re:Never gonna be as good as thermite. (Score:1)
C4
a very strong electromagnete
a bottle of coke