# Will a semi-hyperelliptic pairing be used in real-world cryptography if it is faster than state-of-the-art elliptic pairings?

Let $$\mathbb{G}_1$$, $$\mathbb{G}_2$$, $$\mathbb{G}_T$$ stand for three groups of the same large prime order $$r$$. I invented a pairing $$e\!: \mathbb{G}_1 \times \mathbb{G}_2 \to \mathbb{G}_T$$ (with embedding degree $$k \in \mathbb{N}$$) such that $$\mathbb{G}_1 \subset J(\mathbb{F}_p), \qquad \mathbb{G}_2 \subset E(\mathbb{F}_{p^n}), \qquad \mathbb{G}_T \subset \mathbb{F}_{p^k}^*,$$ where $$J$$ is the Jacobian of some (hyperelliptic) curve of genus $$2$$ over a finite field $$\mathbb{F}_p$$ (of large characteristic) and $$E$$ is an elliptic curve over some extension $$\mathbb{F}_{p^n}$$.

For comparison, let's consider any other elliptic pairing $$e^\prime\!: \mathbb{G}_1^\prime \times \mathbb{G}_2^\prime \to \mathbb{G}_T^\prime$$ (with embedding degree $$d \in \mathbb{N}$$) such that $$\mathbb{G}_1^\prime \subset E_1(\mathbb{F}_{q}), \qquad \mathbb{G}_2^\prime \subset E_2(\mathbb{F}_{q^m}), \qquad \mathbb{G}_T^\prime \subset \mathbb{F}_{q^d}^*,$$ where $$E_1$$, $$E_2$$ are some elliptic curves over finite fields $$\mathbb{F}_{q}$$, $$\mathbb{F}_{q^m}$$, respectively ($$p$$ is not necessarily the characteristic of $$\mathbb{F}_q$$). Here $$\mathbb{G}_1^\prime$$, $$\mathbb{G}_2^\prime$$, $$\mathbb{G}_T^\prime$$ are three more groups of the same large prime order $$r^\prime$$. Of course, I suppose that $$p^2 \approx q$$, and $$p^k \approx q^d$$, and $$r \approx r^\prime$$. However, it turns out that $$p^n \ll q^m$$ for my pairing. In other words, the arithmetic in $$\mathbb{G}_2$$ is more efficient than in $$\mathbb{G}_2^\prime$$. In turn, it is recognized that the arithmetic of $$J(\mathbb{F}_{p})$$ (i.e., $$\mathbb{G}_1$$) is comparable in complexity to that of $$E_1(\mathbb{F}_q)$$ (i.e., $$\mathbb{G}_1^\prime$$). Clearly, the same is true in general for the pair $$\mathbb{G}_T$$, $$\mathbb{G}_T^\prime$$.

What if I show that the new semi-hyperelliptic pairing $$e$$ can be evaluated faster than $$e^\prime$$ ? Will this result be groundbreaking or not ? If so, has $$e$$ a chance to be used in real-world cryptography ? I ask you, because for all its long time of existence, hyperelliptic cryptography has not found concrete applications in practice. Although certain earlier articles concluded that, with the proper choice of a genus $$2$$ curve, the group law on its Jacobian can be (slightly) cheaper than on elliptic curves with the same security level.

I would be very grateful to you for any comments.

• More precisely, the advantage of $\mathbb{G}_2$ over $\mathbb{G}_2^\prime$ is the following: $\log_2(p^n)/\log_2(q^m) \approx n/(2m) \approx 3/4$. Aug 5 at 8:28
• And the value $\rho := 2\log_2(p)/\log_2(r)$ can be bounded as follows: $2 < \rho < 3$. It is not small enough in comparison with elliptic pairings. Maybe, in the future there will be pairing-friendly genus $2$ curves with $1 \leqslant \rho \leqslant 2$. Such $\rho$-values are currently used in practice. Aug 5 at 9:02