How can you protect a remailer's keys?

[Chris Adams]

>> The best solution I could come up with (and was willing to write and use)
>> is to specify the passphrase on the command line argument to the compiler

>A far better solution would be to have a long-running daemon hold the
>secret key.  The mixmaster client could talk to the key daemon through
>a unix-domain socket with the permission bits set such that only the
>mixmaster user can connect.  Each time the machine is rebooted, the
>operator must start the daemon and give it a passphrase.

>Second, if your machine is seized or someone gains unauthorized
>physical access to it, the easiest way to get a root shell is by
>rebooting single-user.  However, if the only cleartext copy of a key
>is in memory rather than in the filesystem, once the machine is
>rebooted the secret key is lost.


How about adding an "Oh s___" feature that would dump the key? You could
even tie it to a login attempt (i.e. be sneaky and rename the actual root
account to something else. Possibly hack the login client to return
"root" as the username, etc, etc to complete the illusion if they are
using TEMPEST.  Then set it so that a root login makes the daemon dump
the password)

This would have possibilities, too, if you made it react to a) certain
files in certain directories, b) certain signals or c) certain network
messages.
This would allow you to put in an innocous clear signal. Set it to a temp
file created when editing your remailer's configuration (or userlist).
Make it so that you have to conciously DISABLE security or it dumps the
password. Have an innocent program terminate it. Be able to cancel it by
sending an email (or using telnet) - this would be great if you had a
trusted friend.  Also, with some modification, you could set it to react
to an external stimulus - say a panic button? or a card lock?  You could
even have fun putting all your sensitive stuff on an external hard drive
and rigging your panic button to a) stop the remailer and b) activate the
thermite charge on the external drive.
// This was typed on a Warped PC by an equally warped Chris Adams <adamsc at io-online.com>
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// Opinions expressed are not necessarily my own, much less another's.

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