Uhhh, nope. RC5 sucks on 64-bit machines because Rivest purposely
designed it for Intel chips with lots of 32-bit rotates:
y := x <<< s
becomes something like:
s := s & 31
y := (x << s) & 0xffffffff | (x >> 32-s)
i.e. six instructions! So my Alpha only gets 620K iters/sec. But
don't worry, Wayne and I are plenty busy with another challenge,
finding a discrete log on an elliptic curve... we've got a little over
4 GHz worth of Alphas attacking it and have done 980 billion
iterations so far.
Later, Borkfusters!
-- R.