math/: Improve some commentary in the binary-field arithmetic.

[catacomb] / math / ec-bin.c

diff --git a/math/ec-bin.c b/math/ec-bin.c
index d91b034340237d472ed53326223cadd813d7de2b..c7fe96d499fd08e67ddafc8d6879ccc6c21e7588 100644 (file)
--- a/math/ec-bin.c
+++ b/math/ec-bin.c
@@ -73,6 +73,7 @@ static ec *ecfind(ec_curve *c, ec *d, mp *x)
       v = F_MUL(f, v, u, y);       /* %$B = A x^{-2} = x + a + b x^{-2}$% */
       y = F_QUADSOLVE(f, y, v);                /* %$z^2 + z = B$% */
       if (y) y = F_MUL(f, y, y, x);    /* %$y = z x$% */
+      /* Hence %$y^2 + x y = (z^2 + z) x^2 = A$% */
     }
     MP_DROP(u);
     MP_DROP(v);