David Honig wrote:
At 05:31 PM 12/5/00 -0500, R. A. Hettinga wrote:
An instructive case. Apparently they used the keystroke monitoring to obtain the pgp passphrase, which was then used to decrypt the files.
A PDA would have been harder to hack, one imagines.
Are there padlockable metal cases for PDAs?
As I've written, the FBI should run quality house cleaning services in large cities.
Physical locks can be picked. I doubt it's worth bothering with unless someone can figure out a good protocol to implement. Why? Simple. Two words: Hardware access. Once you have access to the hardware, including installing both hardware and software sniffers, the game is over. The attacker isn't after your passphrase just to have the passphrase. The attacker is after your data. He wants access to what's in that encrypted email or file. And how does that data get encrypted? You type it in. Or you print or display it. At those two points, someone with hardware access can get to your data without having your passphrase by bugging your keyboard, monitor's output, or printer output. If you type in your messages on the PC and encrypt them before you send them, what's the use? A Keyboard sniffer has already got the message you think you've encrypted. But since you have to type in your passphrase to access the data, they have your passphrase also. Let's go back to using a PDA, ring or other access method: 1. If you simply send your passphrase over a serial port, USB port, IR, ethernet, or any other kind of communications bus, it can be captured. 2. You can do other things such as send the encrypted key to the PDA, have the PDA decrypt it after it asks its owner for a passphrase (and salt with timestamps) but once the key is on the (untrusted) PC, its as good as captured, and so is the data. 3. If you do all the crypto on the PDA (mighty slow unless you've got a beefy PDA) you're choked by the communication method's throughput - which isn't bad over USB. *But* if you display anything on the PC it too can be captured. Bottom line: Unless you can handcuff a notebook to yourself 24/7/365 and never sleep, it's mighty damned hard to trust it. There's always some intrusion vector via the hardware. You can harden your hardware against tampering, which is a guaranteed way to bring up the topic of exploding hard drives, etc. :) And both myself and Tim will tell you "Look in the Archives, we've talked about this to death already." Another option is to have a small portable fully functional computer and just use a big USB/Firewire/SCSI disk to store the encrypted data. Since all the sectors read/written on this drive are encrypted, hardware access to the hard drive gains your attacker nothing. At best they can only damage the drive, which if you have backups is a negligible annoyance. For civilized attackers, remember there is TEMPEST monitoring to worry about. For less civilized attackers: You can be mugged or robbed, but if they get your notebook without the passphrase, it's a waste of their time. So if the notebook is returned to you, sell it on eBay and setup a new one. And at some point, even if you have your notebook with you at all times, you will fall asleep - naturally or with the help of a sleeping pill in your drink, etc. When you do, your attacker has physical access to your notebook, and to you. And when you wake, you may find the rubber hoses awaiting deployment. Now, for extra credit, dear punks, mull over a protocol or way to prevent the above attack vectors. And be sure to include a special passphrase for the rubber hose treatments. Perhaps a few layers of them, so when they beat you for the 2nd passphrase you can give them a slightly more incriminating passphrase, but still not a fully damaging one. -- ----------------------Kaos-Keraunos-Kybernetos--------------------------- + ^ + :Surveillance cameras|Passwords are like underwear. You don't /|\ \|/ :aren't security. A |share them, you don't hang them on your/\|/\ <--*-->:camera won't stop a |monitor, or under your keyboard, you \/|\/ /|\ :masked killer, but |don't email them, or put them on a web \|/ + v + :will violate privacy|site, and you must change them very often. --------_sunder_@_sunder_._net_------- http://www.sunder.net ------------