--- /dev/null
+/* -*-c-*-
+ *
+ * Arithmetic modulo 2^255 - 19
+ *
+ * (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.
+ */
+
+#ifndef CATACOMB_F25519_H
+#define CATACOMB_F25519_H
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "fake-mLib-bits.h"
+
+#ifndef CATACOMB_QFARITH_H
+# include "qfarith.h"
+#endif
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef union {
+ int32 p26[10];
+} f25519;
+
+/*----- 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_pick2@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@)
+ * @const f25519 *x, *y@ = two operands
+ * @uint32 m@ = a mask
+ *
+ * Returns: ---
+ *
+ * Use: If @m@ is zero, set @z = y@; if @m@ is all-bits-set, then set
+ * @z = x@. If @m@ has some other value, then scramble @z@ in
+ * an unhelpful way.
+ */
+
+extern void f25519_pick2(f25519 */*z*/, const f25519 */*x*/,
+ const f25519 */*y*/, uint32 /*m*/);
+
+/* --- @f25519_pickn@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result
+ * @const f25519 *v@ = a table of entries
+ * @size_t n@ = the number of entries in @v@
+ * @size_t i@ = an index
+ *
+ * Returns: ---
+ *
+ * Use: If @0 <= i < n < 32@ then set @z = v[i]@. If @n >= 32@ then
+ * do something unhelpful; otherwise, if @i >= n@ then set @z@
+ * to zero.
+ */
+
+extern void f25519_pickn(f25519 */*z*/, const f25519 */*v*/, size_t /*n*/,
+ size_t /*i*/);
+
+/* --- @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_neg@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@)
+ * @const f25519 *x@ = an operand
+ *
+ * Returns: ---
+ *
+ * Use: Set @z = -x@.
+ */
+
+extern void f25519_neg(f25519 */*z*/, const f25519 */*x*/);
+
+/* --- @f25519_condneg@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@)
+ * @const f25519 *x@ = an operand
+ * @uint32 m@ = a mask
+ *
+ * Returns: ---
+ *
+ * Use: If @m@ is zero, set @z = x@; if @m@ is all-bits-set, then set
+ * @z = -x@. If @m@ has some other value then scramble @z@ in
+ * an unhelpful way.
+ */
+
+extern void f25519_condneg(f25519 */*z*/, const f25519 */*x*/, uint32 /*m*/);
+
+/* --- @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*/);
+
+/* --- @f25519_quosqrt@ --- *
+ *
+ * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@)
+ * @const f25519 *x, *y@ = two operands
+ *
+ * Returns: Zero if successful, @-1@ if %$x/y$% is not a square.
+ *
+ * Use: Stores in @z@ the one of the square roots %$\pm\sqrt{x/y}$%.
+ * If %$x = y = 0% then the result is zero; if %$y = 0$% but %$x
+ * \ne 0$% then the operation fails. If you wanted a specific
+ * square root then you'll have to pick it yourself.
+ */
+
+extern int f25519_quosqrt(f25519 */*z*/,
+ const f25519 */*x*/, const f25519 */*y*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+ }
+#endif
+
+#endif
~mdw / secnet / blobdiff