A Naive Signing Function
Recall that the signing function computes
s = xe mod m
where x is the message.
The exponent e is computed from 100-digit prime numbers p and q, so
it is also large. See the signing-exponent in naive.rkt at right.
If you try to obtain the signature by using the sign function
below, you will run out of memory and time.
To store the number resulting from (expt message signing-exponent),
you would need far more memory than there are sub-atomic
particles in the observable universe. (See pp. 89-90 of text)