On Tue, Dec 19, 2000 at 09:05:17PM +0100, Manuel Bouyer wrote:

 > I'm not sure this is the best, because you could have to encrypt/decrypt
 > to much data, which will hurt performances. You may also run in the
 > problem that the crypted data are biggers than the original.
 > A way to do this would be to write a layered filesystem that files, and
 > possibly files names in directory.

For all ciphers that we currently use in the NetBSD kernel, the output
size is the same as the input size.  Obviously the input size has to be
rounded to the cipher's block size, if you're using a block cipher, but
for disk blocks, that should pretty much always be the case.

Are there any currently-used ciphers that actually have different sizes
for input vs. output data?

-- 
        -- Jason R. Thorpe <thorpej@zembu.com>