[Remops] [Mixmaster-devel] mixmaster 3 key lifetimes

[lists at notatla.org.uk]

A patch is attached.

1. Old secret keys are to be deleted automatically after expiry.
    (I was surprised to see that was not already happening.  An adversary
     capturing your old keyfile seems able to decrypt old messages.)
    This patch overwrites the old file after replacing it with a new one
    that no longer contains the expired keys.

    I encourage operators to check whether they have unwanted secret keys
    still present on their systems.

2. A new command-line option enables you to set a key lifetime.
    mixmaster -G --lifetime=28
    If you do not specify the lifetime (in days) the default is used.

    If a remailer has a long-term key (such as 1 year) as well
    as generating a short-term key each day then someone who wanted to
    could choose a key that was close to expiry and less at risk of
    disclosure.
    (Automation of that would require changes in the client.)

    (Plus a greater volume of 1024-bit keys is more work for anyone
    factoring the remailer keys.)

3. A new file contains all public keys for your remailer.

Keep up the good work.
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