Some time ago I’ve generated colored addition/multiplication tables in order to visualize group structure. My idea was to compare extension fields of same order with different reduction polynomials, and to compare elliptic curve groups with groups of integers modulo a prime (). However, as pointed out by an attentive reader, I’ve messed up claiming that the latter group is used by RSA. It is not, it’s used for e.g. DSA, while RSA uses a composite modulus: the product of two prime numbers.

So, how do and compare?