“…The main example is provided by elliptic curves over finite fields, whose use in cryptography was introduced, independently, by Koblitz [12] and Miller [17]. Moreover, curves with a group's structure, usually cubics or conics, can be exploited for constructing RSA-like schemes (see, e.g., [4,8,13,19,20,22,23,24]), for improving the performances in the decryption procedures, and having also more security than RSA in some contexts, like broadcast scenarios. Many of these cryptosystems were studied exploiting the properties of the Pell's hyperbola that is the set of solutions in a field F of the famous Pell's equation x 2 −Dy 2 = 1, with D ∈ F * , like in [5], where the authors exhibited an RSA-like cryptosystem over the Pell's hyperbola exploiting multi-factor moduli.…”