On Mon, 08 Sep 2003, Jun-ichiro itojun Hagino wrote:
>       we have needs for 16bit and 20bit, do you know of 16/20bit block
>       cipher?

Since the high bit is used for a special purpose (toggled every time
the generator is reseeded), don't we actually need 15- and 19-bit block
ciphers to generate 16- and 20-bit identifiers?

I believe that you can build a block cipher of arbitrary size using
a Feistel network and some other cipher.  See recent posts to the
cryptography@metzdowd.com list.

--apb (Alan Barrett)