s/bit/bits/

s/by using/in/

<para> should be on a new line after <listitem>

Terms need to be in <literal></literal>.

Do we have other places that use this term, space, dash, space, sentence format? This might work better with a <variablelist>, although I don't know about using <literal> for the term.

s/a list of/the/

Simplify:

key lengths that are supported by each encryption algorithm.

"The size of the sectors used for encryption." does not really help. A reader could take that to mean something to do with the encryption algorithm or number of passes instead of the amount of data to encrypt at a time.

s/as/at/

</listitem> on a new line.

s/encryption/an encrypted swap device/

I still think that just "encryption" here is too vague. The example shows how to configure an an encrypted swap device, not just encryption in general.