version 1.1.1.1, 2000/01/10 15:35:27 |
version 1.1.1.3, 2003/08/25 16:06:33 |
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/* mpz_invert (inv, x, n). Find multiplicative inverse of X in Z(N). |
/* mpz_invert (inv, x, n). Find multiplicative inverse of X in Z(N). |
If X has an inverse, return non-zero and store inverse in INVERSE, |
If X has an inverse, return non-zero and store inverse in INVERSE, |
otherwise, return 0 and put garbage in X. |
otherwise, return 0 and put garbage in INVERSE. |
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Copyright (C) 1996 Free Software Foundation, Inc. |
Copyright 1996, 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc. |
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This file is part of the GNU MP Library. |
This file is part of the GNU MP Library. |
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The GNU MP Library is free software; you can redistribute it and/or modify |
The GNU MP Library is free software; you can redistribute it and/or modify |
it under the terms of the GNU Library General Public License as published by |
it under the terms of the GNU Lesser General Public License as published by |
the Free Software Foundation; either version 2 of the License, or (at your |
the Free Software Foundation; either version 2.1 of the License, or (at your |
option) any later version. |
option) any later version. |
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The GNU MP Library is distributed in the hope that it will be useful, but |
The GNU MP Library is distributed in the hope that it will be useful, but |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
License for more details. |
License for more details. |
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You should have received a copy of the GNU Library General Public License |
You should have received a copy of the GNU Lesser General Public License |
along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
MA 02111-1307, USA. */ |
MA 02111-1307, USA. */ |
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#include "gmp.h" |
#include "gmp.h" |
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#include "gmp-impl.h" |
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int |
int |
#if __STDC__ |
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mpz_invert (mpz_ptr inverse, mpz_srcptr x, mpz_srcptr n) |
mpz_invert (mpz_ptr inverse, mpz_srcptr x, mpz_srcptr n) |
#else |
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mpz_invert (inverse, x, n) |
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mpz_ptr inverse; |
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mpz_srcptr x, n; |
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#endif |
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{ |
{ |
mpz_t gcd; |
mpz_t gcd, tmp; |
int rv; |
mp_size_t xsize, nsize, size; |
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TMP_DECL (marker); |
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mpz_init (gcd); |
xsize = SIZ (x); |
mpz_gcdext (gcd, inverse, (mpz_ptr) 0, x, n); |
nsize = SIZ (n); |
rv = gcd->_mp_size == 1 && (gcd->_mp_d)[0] == 1; |
xsize = ABS (xsize); |
mpz_clear (gcd); |
nsize = ABS (nsize); |
return rv; |
size = MAX (xsize, nsize) + 1; |
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/* No inverse exists if the leftside operand is 0. Likewise, no |
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inverse exists if the mod operand is 1. */ |
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if (xsize == 0 || (nsize == 1 && (PTR (n))[0] == 1)) |
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return 0; |
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TMP_MARK (marker); |
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MPZ_TMP_INIT (gcd, size); |
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MPZ_TMP_INIT (tmp, size); |
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mpz_gcdext (gcd, tmp, (mpz_ptr) 0, x, n); |
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/* If no inverse existed, return with an indication of that. */ |
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if (SIZ (gcd) != 1 || PTR(gcd)[0] != 1) |
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{ |
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TMP_FREE (marker); |
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return 0; |
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} |
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/* Make sure we return a positive inverse. */ |
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if (SIZ (tmp) < 0) |
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{ |
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if (SIZ (n) < 0) |
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mpz_sub (inverse, tmp, n); |
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else |
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mpz_add (inverse, tmp, n); |
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} |
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else |
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mpz_set (inverse, tmp); |
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TMP_FREE (marker); |
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return 1; |
} |
} |