X-Git-Url: https://git.distorted.org.uk/~mdw/secnet/blobdiff_plain/ae8cd973b817f81c075ab20e84d3239125146f24..8a7654a695e8ecdc8c14dced445839a7a7e6a8ca:/x448.c

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+/* -*-c-*-
+ *
+ * The X448 key-agreement algorithm
+ *
+ * (c) 2017 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of secnet.
+ * See README for full list of copyright holders.
+ *
+ * secnet is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version d of the License, or
+ * (at your option) any later version.
+ *
+ * secnet is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 3 along with secnet; if not, see
+ * https://www.gnu.org/licenses/gpl.html.
+ *
+ * This file was originally part of Catacomb, but has been automatically
+ * modified for incorporation into secnet: see `import-catacomb-crypto'
+ * for details.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "fake-mLib-bits.h"
+
+#include "montladder.h"
+#include "fgoldi.h"
+#include "x448.h"
+
+/*----- Important constants -----------------------------------------------*/
+
+const octet x448_base[56] = { 5, 0, /* ... */ };
+
+#define A0 39081
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @x448@ --- *
+ *
+ * Arguments:	@octet zz[X448_OUTSZ]@ = where to put the result
+ *		@const octet k[X448_KEYSZ]@ = pointer to private key
+ *		@const octet qx[X448_PUBSZ]@ = pointer to public value
+ *
+ * Returns:	---
+ *
+ * Use:		Calculates X448 of @k@ and @qx@.
+ */
+
+void x448(octet zz[X448_OUTSZ],
+	  const octet k[X448_KEYSZ],
+	  const octet qx[X448_PUBSZ])
+{
+  uint32 kw[14];
+  fgoldi x1;
+  unsigned i;
+
+  /* Load and clamp the key.  The low bits are cleared to kill the small
+   * subgroups on the curve and its twist, and a high bit is set to guard
+   * against careless implementations, though this isn't one of those.
+   */
+  for (i = 0; i < 14; i++) kw[i] = LOAD32_L(k + 4*i);
+  kw[0] &= 0xfffffffc; kw[13] |= 0x80000000;
+
+  /* And run the ladder. */
+  fgoldi_load(&x1, qx);
+#define MULA0(z, x) do { fgoldi_mulconst((z), (x), A0); } while (0)
+  MONT_LADDER(fgoldi, MULA0, kw, 14, 32, &x1, &x1);
+#undef MULA0
+  fgoldi_store(zz, &x1);
+}
+
+/*----- That's all, folks -------------------------------------------------*/