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Crypto n stuff

Name: Bonersconer 2012-07-04 4:03

I am not a noob, nor am I experienced in these areas, modesty is a safe bet as I do not want to overstate my skillset.

I have two sources that I consider to be the people with the most experience that I know in these areas but they do not fully agree. I would like to get your opinions and whatever else you may want to share about what you do and why.

Friend 1, computer professional, runs his own business out of his house fixing peoples shit and tinkering with his own tech. Recommends LUKS for encrypting non-OS files (for speed) and temporary files and important data. Thinks truecrypt is garbage because its proprietary.

For deletion he uses dd and dev/zero. On his ext4 filesystem it takes 2 hours to dd and 2 minutes to LUKS a 300gb drive. He suspects that dev/zero over dev/urandom contributes a bit (he admitted he doesn't know how much cause he doesn't use urandom) but he thinks that the NTFS filesystem is the cause of the slow (20GB/hour) dd speed. He also said, when I brought up the idea that dev/zero with dd is less secure and determined people could see what was written on the disk before all the 0's because they're all 0's and its easy to see ( read a paranoid theory about this idea) and he said that with NTFS that'd be possible but not other filesystems.

His paranoia solution was dd, format, encrypt with random salt (I'm unsure what this is, something about password security) and then format  with a different filesystem and use that one after encrypting. He also mentioned setting up encryption to randomize keys on bootup for your temp files and pagefile where your encryption passwords are stored.

Friend 2 said that dd dev/urandom with a few passes to be safe was a good idea and that Truecrypt is trustworthy. He also recommended using a bootable USB OS over a hard drive.

Please criticize all of these assumptions as I am here to learn what is correct.

Name: Anonymous 2012-07-05 21:42

>>11

Oh right, and the stuff about USB OS over HDD OS is pointless. I guess if you want to be able to swallow your hard drive or keep all your data in your pocket any time your computer isn't on, but otherwise, with full disk encryption the integrity of your data is assured. Just put your boot partition on a USB stick or MicroSD card, that's the only partition that can't be encrypted. If you keep that on you at all times, then no one will be able to mess with the OS while the computer is off. So that someone wouldn't be able to modify the kernel and mess with the scheme. People could still install hardware keyloggers and other hardware fuckery, so keep that in mind.

You can use keyfiles too, but it isn't really necessary in my opinion. The way AES-256 works, a 39 character completely random (or as "random" as it will get) ASCII passphrase is the maximum amount of security you can get. This will get transformed into a 32-byte Key by the Password Based Key Derivation Function anyway, so after 39 ASCII characters you start running into collisions. Having >100 char passwords or multiple keyfiles won't do anything other than increasing the risk of data loss when you forget the passphrase / lose the USB sticks the keyfiles are on.

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