>A friend of mine tried once to make backups of an encrypted filesystem.
>That looked easy: just put on a tape/zip/whatever the file containing the
>encrypted filesystem. He found out however that that was not doable: each
>block of data is encrypted using a seed which is the __absolute__ block
>number of the underlying filesystem, where it should be the block number
>__relative__ to the beginning of the file containing the encrypted
>filesystem. The consequence is that if you try to restore a backup (or
>simply if you try to copy the encrypted filesystem), you obtain something
>which cannot be decrypted as the block numbers have changed since the
>encryption.
>From the current .../linux/Documentation/crypto/ChangeLog (after
applying the Linux-int patch):
: * International kernel patch 2.2.10.4 released.
:
: * Added new config option for using relative block numbers instead
: of absolute ones when calling the loop block device's transfer
: function. This should fix the #1 issue with using loopback crypto
: filesystems.
Regards,
Ernst
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