Re: Proposal for keying encrypted filesystem

[Edward Shushkin <edward@namesys.com>]

Pierre Abbat wrote:
> 
> Each file has a four-byte key ID in its inode and is encrypted with a longer
> key. (One way to make these keys is to hash a passphrase with SHA1 and use
> four bytes for the key ID and the rest for the key.) Each process may hold
> any number of credentials consisting of the key ID and the key. When a
> process attempts to open an encrypted file, the kernel checks whether it or
> any of its ancestors has a credential that matches the file's key ID.

Never trust 4-byte ID. The first collision that provides any assigned 4 bytes 
in SHA1 output can be found very easy..

Edward.

> 
> A utility called reiserkey is used to set and unset these keys. It can set or
> unset the key in itself or any of its ancestors running under the same uid,
> or if it's running as root, in any of its ancestors. reiserkey -a n sets the
> key in the nth ancestor; reiserkey -p n sets the key in process n. The
> default is -a 1; if reiserkey is run from a shell script, this sets the key
> in the shell script. To set it system-wide, use -p 1.
> 
> phma
> --
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