On a article of Wikipedia (http://en.wikipedia.org/wiki/Substitution_box ), we can found a example of 6×4-bit S-box (from DES). So this S-box work with a input of 6-bit and and output of 4-bits and of cours we can see that:
input.length > output.length
But I can't imagine a 8×32-bit S-boxes, like in CAST-128 function (http://en.wikipedia.org/wiki/CAST-128) or in Blowfish (http://en.wikipedia.org/wiki/Blowfish_%28cipher%29), when the output length is bigger then the input length.
I you have a example, it should be very helpful.
Thanks you for your help.