Re: mlock(1)

[Wolfgang Walter <ml-linux-kernel@studentenwerk.mhn.de>]

> Basically to avoid to type the password during suspend, we'd need an
> algorihtm that encrypts with a public key stored on the harddisk and
> restore with the private key that sits only on a human brain.  The
> public key would be stored on the harddisk and it would be used by
> suspend to write to the swap partition. the resume password would be
> asked to the user and used to decrypt the data. I think it should work
> fine in theory.
>
> However AFIK those public/private key algorithms only works securely with
> tons of bits (a lot more than with a symmetic encryption), so I don't see
> how can an human could possibly remeber such a long private key by memory.
> I guess to make it work you'd need an USB pen to store it and unplug it
> (then you'd have to be careful not to lose the USB pen). So I think it's
> much simpler to use symmetric crypto (like cryptoloop) and to ask the
> password during suspend too.

You may do it like ssh: encrypt the private key with a symmetric cypher using 
a key based on a passphrase and store it on disk (of course this is only as 
secure as your passphrase).

On suspend: generate a symmetric-key KS, save memory to harddisk encrypted 
with KS, append the KS enrypted with the public key A_PUB. append the private 
encrypted key A_PRIV_ENCR_BASED_ON_PASSPHRASE  (which is stored on the 
harddisk). On resume user must type in passphrase, then we can decrypt 
A_PRIV_ENCR_BASED_ON_PASSPHRASE and get A_PRIV, decrypt KS and so decrypt 
saved memory.

Greetings,

Wolfgang Walter
-- 
Wolfgang Walter
Studentenwerk München
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