23 Oct 2000 (updated 23 Oct 2000 at 22:25 UTC)
»
DES
Yeah, yeah - DES is old news, but I wanted to start
simple, so DES it is. I've written a naive DES
implementation, optimisation comes next, then the
software/hardware hybrid. Then something more whizzy like
Rijndael.
But... there's always a but isn't there? I have got
my
DES implementation to a stage where:
D(E(x)) = x
However, when I run the test cases I've found on the
web,
they don't show the correct ciphertext for a given
plaintext/key combination. I've got a feeling that it lies
in the bit ordering - all the documentation starts with the
LSB on the left - but they continue this notation down to
the hex values - to decimal five would be written in hex as
A - because the binary is 1010. I'm confused. I can't really
find documentation to back up this suspition, but the blank
key with the parity bits every eigth bit is written
0x0101010101010101, rather than 0x8080808080808080 as I'd
expect.
I'll try munging some things tomorrow to try and fix
it,
but as I'm doing it as an academic exercise - i.e. I need
the general alg, and something which will do D(E(x)) = x,
but I don't need to interface with other DES software, I
think I'll leave it if there is no obvious solution. Perhaps
I can call it D35 :-)
Music
Generally I try and keep it just coding up here, but
seeing as Kid A generated so much traffic on here, I thought
I'd add a couple of recommendations. First is Black Market
Music by Placebo and the second is Showbiz by Muse. Saw
Placebo live last weekend in Glasgow. Really good show. The
album is more pop than there last album (which I think is
the best they've done). Muse are new to me, but I keep
seeing
them live on tele and they're really good.
Misc
The webcam
is
broken, but I've just not had time to look into the why yet
- been too busy.