Commit b6c44563 authored by Niels Möller's avatar Niels Möller
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Fixed equations for Montgomery->Edwards transformation.

parent 131d068d
...@@ -127,7 +127,7 @@ mapping $P = (x,y)$ to $P' = (u, v)$, as follows. ...@@ -127,7 +127,7 @@ mapping $P = (x,y)$ to $P' = (u, v)$, as follows.
that $x^2 + bx + 1 = 0$, or $(x + b/2)^2 = (b/2)^2 - 1$, which also that $x^2 + bx + 1 = 0$, or $(x + b/2)^2 = (b/2)^2 - 1$, which also
isn't a quadratic residue). The correspondence is then given by isn't a quadratic residue). The correspondence is then given by
\begin{align*} \begin{align*}
u &= \sqrt{b} \, x / y \\ u &= \sqrt{b+2} \, x / y \\
v &= (x-1) / (x+1) v &= (x-1) / (x+1)
\end{align*} \end{align*}
\end{itemize} \end{itemize}
...@@ -135,7 +135,7 @@ mapping $P = (x,y)$ to $P' = (u, v)$, as follows. ...@@ -135,7 +135,7 @@ mapping $P = (x,y)$ to $P' = (u, v)$, as follows.
The inverse transformation is The inverse transformation is
\begin{align*} \begin{align*}
x &= (1+v) / (1-v) \\ x &= (1+v) / (1-v) \\
y &= \sqrt{b} x / u y &= \sqrt{b+2} x / u
\end{align*} \end{align*}
If the Edwards coordinates are represented using homogeneous If the Edwards coordinates are represented using homogeneous
coordinates, $u = U/W$ and $v = V/W$, then coordinates, $u = U/W$ and $v = V/W$, then
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