| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Utilities for quick field arithmetic |
| 4 | * |
| 5 | * (c) 2017 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of secnet. |
| 11 | * See README for full list of copyright holders. |
| 12 | * |
| 13 | * secnet is free software; you can redistribute it and/or modify it |
| 14 | * under the terms of the GNU General Public License as published by |
| 15 | * the Free Software Foundation; either version d of the License, or |
| 16 | * (at your option) any later version. |
| 17 | * |
| 18 | * secnet is distributed in the hope that it will be useful, but |
| 19 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
| 20 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 21 | * General Public License for more details. |
| 22 | * |
| 23 | * You should have received a copy of the GNU General Public License |
| 24 | * version 3 along with secnet; if not, see |
| 25 | * https://www.gnu.org/licenses/gpl.html. |
| 26 | * |
| 27 | * This file was originally part of Catacomb, but has been automatically |
| 28 | * modified for incorporation into secnet: see `import-catacomb-crypto' |
| 29 | * for details. |
| 30 | * |
| 31 | * Catacomb is free software; you can redistribute it and/or modify |
| 32 | * it under the terms of the GNU Library General Public License as |
| 33 | * published by the Free Software Foundation; either version 2 of the |
| 34 | * License, or (at your option) any later version. |
| 35 | * |
| 36 | * Catacomb is distributed in the hope that it will be useful, |
| 37 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 38 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 39 | * GNU Library General Public License for more details. |
| 40 | * |
| 41 | * You should have received a copy of the GNU Library General Public |
| 42 | * License along with Catacomb; if not, write to the Free |
| 43 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 44 | * MA 02111-1307, USA. |
| 45 | */ |
| 46 | |
| 47 | #ifndef CATACOMB_QFARITH_H |
| 48 | #define CATACOMB_QFARITH_H |
| 49 | |
| 50 | #ifdef __cplusplus |
| 51 | extern "C" { |
| 52 | #endif |
| 53 | |
| 54 | /*----- Header files ------------------------------------------------------*/ |
| 55 | |
| 56 | #include <limits.h> |
| 57 | |
| 58 | #include "fake-mLib-bits.h" |
| 59 | /*----- Signed integer types ----------------------------------------------*/ |
| 60 | |
| 61 | typedef int32_t int32; |
| 62 | typedef int64_t int64; |
| 63 | #define HAVE_INT64 1 |
| 64 | |
| 65 | /*----- General bit-hacking utilities -------------------------------------*/ |
| 66 | |
| 67 | /* Individual bits, and masks for low bits. */ |
| 68 | #define BIT(n) (1ul << (n)) |
| 69 | #define MASK(n) (BIT(n) - 1) |
| 70 | |
| 71 | /* Arithmetic right shift. If X is a value of type TY, and N is a |
| 72 | * nonnegative integer, then return the value of X shifted right by N bits; |
| 73 | * alternatively, this is floor(X/2^N). |
| 74 | * |
| 75 | * GCC manages to compile this into a simple shift operation if one is |
| 76 | * available, but it's correct for all C targets. |
| 77 | */ |
| 78 | #define ASR(ty, x, n) (((x) - (ty)((u##ty)(x)&MASK(n)))/(ty)BIT(n)) |
| 79 | |
| 80 | /*----- Constant-time utilities -------------------------------------------*/ |
| 81 | |
| 82 | /* The following have better implementations on a two's complement target. */ |
| 83 | |
| 84 | /* If we have two's complement arithmetic then masks are signed; this |
| 85 | * avoids a switch to unsigned representation, with the consequent problem |
| 86 | * of overflow when we convert back. |
| 87 | */ |
| 88 | typedef int32 mask32; |
| 89 | |
| 90 | /* Convert an unsigned mask M into a `mask32'. This is a hairy-looking |
| 91 | * no-op on many targets, but, given that we have two's complement |
| 92 | * integers, it is free of arithmetic overflow. |
| 93 | */ |
| 94 | #define FIX_MASK32(m) \ |
| 95 | ((mask32)((m)&0x7fffffffu) + (-(mask32)0x7fffffff - 1)*(((m) >> 31)&1u)) |
| 96 | |
| 97 | /* If Z is zero and M has its low 32 bits set, then copy (at least) the low |
| 98 | * 32 bits of X to Z; if M is zero, do nothing. Otherwise, scramble Z |
| 99 | * unhelpfully. |
| 100 | */ |
| 101 | #define CONDPICK(z, x, m) do { (z) |= (x)&(m); } while (0) |
| 102 | |
| 103 | /* If M has its low 32 bits set, then return (at least) the low 32 bits of |
| 104 | * X in Z; if M is zero, then return (at least) the low 32 bits of Y in Z. |
| 105 | * Otherwise, return an unhelful result. |
| 106 | */ |
| 107 | #define PICK2(x, y, m) (((x)&(m)) | ((y)&~(m))) |
| 108 | |
| 109 | /* If M has its low 32 bits set then swap (at least) the low 32 bits of X |
| 110 | * and Y; if M is zero, then do nothing. Otherwise, scramble X and Y |
| 111 | * unhelpfully. |
| 112 | */ |
| 113 | #define CONDSWAP(x, y, m) \ |
| 114 | do { mask32 t_ = ((x) ^ (y))&(m); (x) ^= t_; (y) ^= t_; } while (0) |
| 115 | |
| 116 | /* Return zero if bit 31 of X is clear, or a mask with (at least) the low 32 |
| 117 | * bits set if bit 31 of X is set. |
| 118 | */ |
| 119 | #define SIGN(x) (-(mask32)(((uint32)(x) >> 31)&1)) |
| 120 | |
| 121 | /* Return zero if X is zero, or a mask with (at least) the low 32 bits set if |
| 122 | * X is nonzero. |
| 123 | */ |
| 124 | #define NONZEROP(x) SIGN((U32(x) >> 1) - U32(x)) |
| 125 | |
| 126 | /*----- Debugging utilities -----------------------------------------------*/ |
| 127 | |
| 128 | /* Define a debugging function DUMPFN, which will dump an integer represented |
| 129 | * modulo M. The integer is represented as a vector of NPIECE pieces of type |
| 130 | * PIECETY. The pieces are assembled at possibly irregular offsets: piece i |
| 131 | * logically has width PIECEWD(i), but may overhang the next piece. The |
| 132 | * pieces may be signed. GETMOD is an expression which calculates and |
| 133 | * returns the value of M, as an `mp *'. |
| 134 | * |
| 135 | * The generated function writes the value of such an integer X to the stream |
| 136 | * FP, labelled with the string WHAT. |
| 137 | * |
| 138 | * The definition assumes that <stdio.h>, <catacomb/mp.h>, and |
| 139 | * <catacomb/mptext.h> have been included. |
| 140 | */ |
| 141 | #define DEF_FDUMP(dumpfn, piecety, piecewd, npiece, noctet, getmod) \ |
| 142 | static void dumpfn(FILE *fp, const char *what, const piecety *x) \ |
| 143 | { \ |
| 144 | mpw w; \ |
| 145 | mp m, *y = MP_ZERO, *t = MP_NEW, *p; \ |
| 146 | octet b[noctet]; \ |
| 147 | unsigned i, o; \ |
| 148 | \ |
| 149 | p = getmod; \ |
| 150 | mp_build(&m, &w, &w + 1); \ |
| 151 | for (i = o = 0; i < npiece; i++) { \ |
| 152 | if (x[i] >= 0) { w = x[i]; m.f &= ~MP_NEG; } \ |
| 153 | else { w = -x[i]; m.f |= MP_NEG; } \ |
| 154 | t = mp_lsl(t, &m, o); \ |
| 155 | y = mp_add(y, y, t); \ |
| 156 | o += piecewd(i); \ |
| 157 | } \ |
| 158 | \ |
| 159 | fprintf(fp, "%s = <", what); \ |
| 160 | for (i = 0; i < npiece; i++) { \ |
| 161 | if (i) fputs(", ", fp); \ |
| 162 | fprintf(fp, "%ld", (long)x[i]); \ |
| 163 | } \ |
| 164 | fputs(">\n\t= ", fp); \ |
| 165 | mp_writefile(y, fp, 10); \ |
| 166 | fputs("\n\t== ", fp); \ |
| 167 | mp_div(0, &y, y, p); \ |
| 168 | mp_writefile(y, fp, 10); \ |
| 169 | fputs("\n\t= 0x", fp); \ |
| 170 | mp_writefile(y, fp, 16); \ |
| 171 | fputs(" (mod 2^255 - 19)\n\t= [", fp); \ |
| 172 | mp_storel(y, b, sizeof(b)); \ |
| 173 | for (i = 0; i < 32; i++) { \ |
| 174 | if (i && !(i%4)) fputc(':', fp); \ |
| 175 | fprintf(fp, "%02x", b[i]); \ |
| 176 | } \ |
| 177 | fputs("]\n", fp); \ |
| 178 | mp_drop(y); mp_drop(p); mp_drop(t); \ |
| 179 | } |
| 180 | |
| 181 | /*----- That's all, folks -------------------------------------------------*/ |
| 182 | |
| 183 | #ifdef __cplusplus |
| 184 | } |
| 185 | #endif |
| 186 | |
| 187 | #endif |