Skip to content

Commit

Permalink
change wording in secp256k1 full torsion
Browse files Browse the repository at this point in the history
  • Loading branch information
PlanetMacro committed May 3, 2024
1 parent 6c32567 commit bbccab3
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion chapters/elliptic-curves-moonmath.tex
Original file line number Diff line number Diff line change
Expand Up @@ -1308,7 +1308,7 @@ \subsection{Full torsion groups}
$$
k = \scriptstyle 192986815395526992372618308347813175472927379845817397100860523586360249056
$$
This means that the embedding degree is very large, which implies that the field extension $\F_{p^k}$ is very large too. To understand how big $\F_{p^k}$ is, recall that an element of $\F_{p^m}$ can be represented as a string $<x_0,\ldots,x_m>$ of $m$ elements, each containing a number from the prime field $\F_p$. Now, in the case of \curvename{secp256k1}, such a representation has $k$-many entries, each of them $256$ bits in size. So, without any optimizations, representing such an element would need $k\cdot 256$ bits, which is too much to be representable in the observable universe. It follows that it is not only infeasible to compute the full $r$-torsion group of \curvename{secp256k1}, but moreover to even write down single elements of that group in general.
This means that the embedding degree is very large, which implies that the field extension $\F_{p^k}$ is very large too. To understand how big $\F_{p^k}$ is, recall that an element of $\F_{p^m}$ can be represented as a string $<x_0,\ldots,x_m>$ of $m$ elements, each containing a number from the prime field $\F_p$. Now, in the case of \curvename{secp256k1}, such a representation has $k$-many entries, each of them $256$ bits in size. So, without any optimizations, representing such an element would need $k\cdot 256$ bits. It follows that it is not only infeasible to compute the full $r$-torsion group of \curvename{secp256k1}, but moreover to even write down single elements of that group in general.
\end{example}
\begin{exercise} Consider the full $5$-torsion group $TJJ\_13[5]$ from \examplename{} \ref{ex:TJJ13-full-torsion}. Write down the set of all elements from this group and identify the subset of all elements from $TJJ\_13(\F_{13})[5]$ as well as $TJJ\_13(\F_{13^2})[5]$. Then compute the $5$-torsion group $TJJ\_13(\F_{13^{8}})[5]$ .
\end{exercise}
Expand Down

0 comments on commit bbccab3

Please sign in to comment.