diff options
Diffstat (limited to 'lib/mpi/mpi-inv.c')
| -rw-r--r-- | lib/mpi/mpi-inv.c | 143 | 
1 files changed, 0 insertions, 143 deletions
| diff --git a/lib/mpi/mpi-inv.c b/lib/mpi/mpi-inv.c deleted file mode 100644 index 61e37d18f793..000000000000 --- a/lib/mpi/mpi-inv.c +++ /dev/null @@ -1,143 +0,0 @@ -/* mpi-inv.c  -  MPI functions - *	Copyright (C) 1998, 2001, 2002, 2003 Free Software Foundation, Inc. - * - * This file is part of Libgcrypt. - * - * Libgcrypt is free software; you can redistribute it and/or modify - * it under the terms of the GNU Lesser General Public License as - * published by the Free Software Foundation; either version 2.1 of - * the License, or (at your option) any later version. - * - * Libgcrypt 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 Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this program; if not, see <http://www.gnu.org/licenses/>. - */ - -#include "mpi-internal.h" - -/**************** - * Calculate the multiplicative inverse X of A mod N - * That is: Find the solution x for - *		1 = (a*x) mod n - */ -int mpi_invm(MPI x, MPI a, MPI n) -{ -	/* Extended Euclid's algorithm (See TAOCP Vol II, 4.5.2, Alg X) -	 * modified according to Michael Penk's solution for Exercise 35 -	 * with further enhancement -	 */ -	MPI u, v, u1, u2 = NULL, u3, v1, v2 = NULL, v3, t1, t2 = NULL, t3; -	unsigned int k; -	int sign; -	int odd; - -	if (!mpi_cmp_ui(a, 0)) -		return 0; /* Inverse does not exists.  */ -	if (!mpi_cmp_ui(n, 1)) -		return 0; /* Inverse does not exists.  */ - -	u = mpi_copy(a); -	v = mpi_copy(n); - -	for (k = 0; !mpi_test_bit(u, 0) && !mpi_test_bit(v, 0); k++) { -		mpi_rshift(u, u, 1); -		mpi_rshift(v, v, 1); -	} -	odd = mpi_test_bit(v, 0); - -	u1 = mpi_alloc_set_ui(1); -	if (!odd) -		u2 = mpi_alloc_set_ui(0); -	u3 = mpi_copy(u); -	v1 = mpi_copy(v); -	if (!odd) { -		v2 = mpi_alloc(mpi_get_nlimbs(u)); -		mpi_sub(v2, u1, u); /* U is used as const 1 */ -	} -	v3 = mpi_copy(v); -	if (mpi_test_bit(u, 0)) { /* u is odd */ -		t1 = mpi_alloc_set_ui(0); -		if (!odd) { -			t2 = mpi_alloc_set_ui(1); -			t2->sign = 1; -		} -		t3 = mpi_copy(v); -		t3->sign = !t3->sign; -		goto Y4; -	} else { -		t1 = mpi_alloc_set_ui(1); -		if (!odd) -			t2 = mpi_alloc_set_ui(0); -		t3 = mpi_copy(u); -	} - -	do { -		do { -			if (!odd) { -				if (mpi_test_bit(t1, 0) || mpi_test_bit(t2, 0)) { -					/* one is odd */ -					mpi_add(t1, t1, v); -					mpi_sub(t2, t2, u); -				} -				mpi_rshift(t1, t1, 1); -				mpi_rshift(t2, t2, 1); -				mpi_rshift(t3, t3, 1); -			} else { -				if (mpi_test_bit(t1, 0)) -					mpi_add(t1, t1, v); -				mpi_rshift(t1, t1, 1); -				mpi_rshift(t3, t3, 1); -			} -Y4: -			; -		} while (!mpi_test_bit(t3, 0)); /* while t3 is even */ - -		if (!t3->sign) { -			mpi_set(u1, t1); -			if (!odd) -				mpi_set(u2, t2); -			mpi_set(u3, t3); -		} else { -			mpi_sub(v1, v, t1); -			sign = u->sign; u->sign = !u->sign; -			if (!odd) -				mpi_sub(v2, u, t2); -			u->sign = sign; -			sign = t3->sign; t3->sign = !t3->sign; -			mpi_set(v3, t3); -			t3->sign = sign; -		} -		mpi_sub(t1, u1, v1); -		if (!odd) -			mpi_sub(t2, u2, v2); -		mpi_sub(t3, u3, v3); -		if (t1->sign) { -			mpi_add(t1, t1, v); -			if (!odd) -				mpi_sub(t2, t2, u); -		} -	} while (mpi_cmp_ui(t3, 0)); /* while t3 != 0 */ -	/* mpi_lshift( u3, k ); */ -	mpi_set(x, u1); - -	mpi_free(u1); -	mpi_free(v1); -	mpi_free(t1); -	if (!odd) { -		mpi_free(u2); -		mpi_free(v2); -		mpi_free(t2); -	} -	mpi_free(u3); -	mpi_free(v3); -	mpi_free(t3); - -	mpi_free(u); -	mpi_free(v); -	return 1; -} -EXPORT_SYMBOL_GPL(mpi_invm); | 
