--- /dev/null
+/* -*-c-*-
+ *
+ * Arithmetic modulo 2^255 - 19
+ *
+ * (c) 2017 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * 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.
+ */
+
+#ifndef CATACOMB_F25519_H
+#define CATACOMB_F25519_H
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <mLib/bits.h>
+
+#ifndef CATACOMB_QFARITH_H
+# include "qfarith.h"
+#endif
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef union {
+ int32 p26[10];
+ int16 p10[26];
+} f25519;
+
+#if !defined(F25519_IMPL) && defined(HAVE_INT64)
+# define F25519_IMPL 26
+#endif
+
+#ifndef F25519_IMPL
+# define F25519_IMPL 10
+#endif
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @f25519_set@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to write the result
+ * @int a@ = a small-ish constant
+ *
+ * Returns: ---
+ *
+ * Use: Sets @z@ to equal @a@.
+ */
+
+extern void f25519_set(f25519 */*x*/, int /*a*/);
+
+/* --- @f25519_load@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to store the result
+ * @const octet xv[32]@ = source to read
+ *
+ * Returns: ---
+ *
+ * Use: Reads an element of %$\gf{2^{255} - 19}$% in external
+ * representation from @xv@ and stores it in @z@.
+ *
+ * External representation is little-endian base-256. Elements
+ * have multiple encodings, which are not produced by correct
+ * software; use of noncanonical encodings is not an error, and
+ * toleration of them is considered a performance feature.
+ *
+ * Some specifications, e.g., RFC7748, require the topmost bit
+ * (i.e., bit 7 of @wv[31]@) to be ignored. Callers
+ * implementing such specifications should clear the bit
+ * explicitly. (It's much easier for a caller who wants the bit
+ * to be ignored to clear it than for a caller who wants the bit
+ * to be significant to apply the necessary change by hand.)
+ */
+
+extern void f25519_load(f25519 */*z*/, const octet /*xv*/[32]);
+
+/* --- @f25519_store@ --- *
+ *
+ * Arguments: @octet zv[32]@ = where to write the result
+ * @const f25519 *x@ = the field element to write
+ *
+ * Returns: ---
+ *
+ * Use: Stores a field element in the given octet vector in external
+ * representation. A canonical encoding is always stored, so,
+ * in particular, the top bit of @xv[31]@ is always left clear.
+ */
+
+extern void f25519_store(octet /*zv*/[32], const f25519 */*x*/);
+
+/* --- @f25519_condswap@ --- *
+ *
+ * Arguments: @f25519 *x, *y@ = two operands
+ * @uint32 m@ = a mask
+ *
+ * Returns: ---
+ *
+ * Use: If @m@ is zero, do nothing; if @m@ is all-bits-set, then
+ * exchange @x@ and @y@. If @m@ has some other value, then
+ * scramble @x@ and @y@ in an unhelpful way.
+ */
+
+extern void f25519_condswap(f25519 */*x*/, f25519 */*y*/, uint32 /*m*/);
+
+/* --- @f25519_add@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@)
+ * @const f25519 *x, *y@ = two operands
+ *
+ * Returns: ---
+ *
+ * Use: Set @z@ to the sum %$x + y$%.
+ */
+
+extern void f25519_add(f25519 */*z*/,
+ const f25519 */*x*/, const f25519 */*y*/);
+
+/* --- @f25519_sub@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@)
+ * @const f25519 *x, *y@ = two operands
+ *
+ * Returns: ---
+ *
+ * Use: Set @z@ to the difference %$x - y$%.
+ */
+
+extern void f25519_sub(f25519 */*z*/,
+ const f25519 */*x*/, const f25519 */*y*/);
+
+/* --- @f25519_mulconst@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@)
+ * @const f25519 *x@ = an operand
+ * @long a@ = a small-ish constant; %$|a| < 2^{20}$%.
+ *
+ * Returns: ---
+ *
+ * Use: Set @z@ to the product %$a x$%.
+ */
+
+extern void f25519_mulconst(f25519 */*z*/, const f25519 */*x*/, long /*a*/);
+
+/* --- @f25519_mul@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@)
+ * @const f25519 *x, *y@ = two operands
+ *
+ * Returns: ---
+ *
+ * Use: Set @z@ to the product %$x y$%.
+ */
+
+extern void f25519_mul(f25519 */*z*/,
+ const f25519 */*x*/, const f25519 */*y*/);
+
+/* --- @f25519_sqr@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@)
+ * @const f25519 *x@ = an operand
+ *
+ * Returns: ---
+ *
+ * Use: Set @z@ to the square %$x^2$%.
+ */
+
+extern void f25519_sqr(f25519 */*z*/, const f25519 */*x*/);
+
+/* --- @f25519_inv@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@)
+ * @const f25519 *x@ = an operand
+ *
+ * Returns: ---
+ *
+ * Use: Stores in @z@ the multiplicative inverse %$x^{-1}$%. If
+ * %$x = 0$% then @z@ is set to zero. This is considered a
+ * feature.
+ */
+
+extern void f25519_inv(f25519 */*z*/, const f25519 */*x*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+ }
+#endif
+
+#endif
~mdw / catacomb / blobdiff