The dice method is great!!! Now I can be sure that my key is a really good key with almost 0 chance of collision 
I wouldn't be so sure. Your private key will probably be full of 7's
http://hyperphysics.phy-astr.gsu.edu/hbase/math/immath/dice.gif
(from http://hyperphysics.phy-astr.gsu.edu/hbase/math/dice.html).
I'd rather flip a coin 256 times. Or better, 256 coins once (decreases the effect of a biased coin)
