creating a secret-carrying box

[Roedy Green]

The closest thing I have found to what I want is a Kanguru AES
Encrypted Flash drive. I key a password to open it. I can then fill
it will secret files which are hardware-encrypted. Then I close it and
nobody can read the files without the password.

HOWEVER, when I take it to another machine, enter the password, it
opens up, but TOO open. ANY app can read it, including spyware.

I am curious about how you might design such a beast without that
problem.

It would be open, but only to one APP. That one app might have to
jump through hoops to retrieve or change data.

One idea I had was to put a little linux OS on the flash drive that
talked HTTPS. It would be like a portable secure server. The app
could pass through a password over HTTPS keyed in. All its
communications would be encrypted.

Another idea I had was to run the app inside the USB drive, and have
it talk to a device driver that would display and accept keystrokes
and mouse strokes for it.

Another related idea was putting some private keys in inaccessible
ROM, and a CPU that could encrypt/decrypt.

 

[Arne Vajhøj]

The closest thing I have found to what I want is a Kanguru AES
Encrypted Flash drive. I key a password to open it. I can then fill
it will secret files which are hardware-encrypted. Then I close it and
nobody can read the files without the password.

HOWEVER, when I take it to another machine, enter the password, it
opens up, but TOO open. ANY app can read it, including spyware.

I am curious about how you might design such a beast without that
problem.

It would be open, but only to one APP. That one app might have to
jump through hoops to retrieve or change data.

One idea I had was to put a little linux OS on the flash drive that
talked HTTPS. It would be like a portable secure server. The app
could pass through a password over HTTPS keyed in. All its
communications would be encrypted.

Another idea I had was to run the app inside the USB drive, and have
it talk to a device driver that would display and accept keystrokes
and mouse strokes for it.

Another related idea was putting some private keys in inaccessible
ROM, and a CPU that could encrypt/decrypt.

I believe the simplest way is to change from file system
level encryption to app encryption.

Now you have some data encrypted on disk, but when you enter the
password the file system automatically decrypt for all access
both the desired app and other apps.

If it is a normal file system but with files encrypted and
decryption being done by the app decrypting, then other apps
can not read the data directly.

There may still be some risk that they hook into the app
that knows how to decrypt.

Arne

 

[Twirlip of the Mists]

The closest thing I have found to what I want is a Kanguru AES
Encrypted Flash drive. I key a password to open it. I can then fill
it will secret files which are hardware-encrypted. Then I close it and
nobody can read the files without the password.

HOWEVER, when I take it to another machine, enter the password, it
opens up, but TOO open. ANY app can read it, including spyware.

I am curious about how you might design such a beast without that
problem.

It would be open, but only to one APP. That one app might have to
jump through hoops to retrieve or change data.

One idea I had was to put a little linux OS on the flash drive that
talked HTTPS. It would be like a portable secure server. The app
could pass through a password over HTTPS keyed in. All its
communications would be encrypted.

Another idea I had was to run the app inside the USB drive, and have
it talk to a device driver that would display and accept keystrokes
and mouse strokes for it.

Another related idea was putting some private keys in inaccessible
ROM, and a CPU that could encrypt/decrypt.

If the drive sends file contents unencrypted to the PC, once the password
has been sent to it, then untrusted apps on the PC can read the drive. So,
you'll need the data to be encrypted in one way or another all the way into
the application you're using it in.

Furthermore, you will need the PC's operating system and all other
kernel-mode code on it to be trusted, as well as the application.
Kernel-mode code can see the contents of the application's address space,
including the data post-decryption, and can also do things like keylogging
while you type in the password.

Your options, as I see them:

1. Only use it from a specific, trusted PC with clean installs of
everything, minimal stuff installed, and preferably no network
connection. Malware either can't get on it or can't phone home
with what it saw.

2. More elaborate: use drive with trusted PC that runs some sort of server.
Less-trusted PC connects to trusted PC via HTTPS or other encrypted
protocol. So, data is encrypted entering less-trusted PC. Both machines
are behind a firewall that will not accept traffic routed to or from the
trusted PC, so the trusted PC can't talk to the internet directly (or be
hacked from it). The semi-trusted PC runs a vetted Linux kernel and
kernel modules, and use of the HTTPS connection is done from an
unprivileged account. That account isn't used for anything else and its
home directory is mounted on a ram drive so anything not saved to the
encrypted drive evaporates every time that machine is reset, limiting
the ability of any malware that infects that account to record anything
for phoning home later. Disconnect the internet before using the drive
and reboot before reconnecting the internet, and malware can't preserve
anything to phone home with. Or, disable networking privileges for that
account (launch a browser sudo root if you need to consult google, or
use your phone or pad or a third computer).

 

[Roedy Green]

can also do things like keylogging
while you type in the password.

The Kanguru people came up with a clever dodge. You can key the
password with your mouse. But the virtual keyboard mutates, so even if
a snoop logs mouse click positions it gives him nothing. He would have
to trap screen contents as well. When you start thinking about a
properly fiendish opponent, it all becomes hopeless.

The most common snoop is a keyboard logger hidden inside the keyboard
where no software security check can find it.

It gets rather amusing. What I have inside my flash drive are files
full of true random numbers, for one-time pad encryption. So it is
sort of nuts to protect them with a lower quality encryption.

Every type of attack you can fend off makes it more costly for some
third party to snoop.

If you getting serious, you might install Linux from purchased CD and
never attach the machine that does any encrypting/decrypting to the
Internet or to a LAN. It would be like the machines the certificate
companies use to guard their master private certificate keys.