Add utilities to create random curve twists.

2 files changed, 35 insertions, 0 deletions

diff --git a/src/math/twists.c b/src/math/twists.c
new file mode 100644
index 0000000..78481f4
--- /dev/null
+++ b/src/math/twists.c
@@ -0,0 +1,18 @@
+/*
+ * ecgen, tool for generating Elliptic curve domain parameters
+ * Copyright (C) 2017-2018 J08nY
+ */
+#include "twists.h"
+
+void curve_twist_rand(curve_t *to, const curve_t *of) {
+	to->field = gcopy(of->field);
+	GEN v = elltwist(of->curve, NULL);
+	to->curve = ellinit(v, to->field, -1);
+	if (typ(of->field) == t_INT) {
+		to->a = ell_get_a4(to->curve);
+		to->b = ell_get_a6(to->curve);
+	} else if (typ(of->field) == t_FFELT) {
+		to->a = ell_get_a2(to->curve);
+		to->b = ell_get_a6(to->curve);
+	}
+}
\ No newline at end of file
diff --git a/src/math/twists.h b/src/math/twists.h
new file mode 100644
index 0000000..3249047
--- /dev/null
+++ b/src/math/twists.h
@@ -0,0 +1,17 @@
+/*
+ * ecgen, tool for generating Elliptic curve domain parameters
+ * Copyright (C) 2017-2018 J08nY
+ */
+#ifndef ECGEN_TWIST_H
+#define ECGEN_TWIST_H
+
+#include "misc/types.h"
+
+/**
+ * @brief Twists the <code>of</code> curve randomly.
+ * @param to The result of the twist.
+ * @param of The curve to be twisted.
+ */
+void curve_twist_rand(curve_t *to, const curve_t *of);
+
+#endif  // ECGEN_TWIST_H