diff options
Diffstat (limited to 'lib/mpi/mpi-inv.c')
| -rw-r--r-- | lib/mpi/mpi-inv.c | 187 |
1 files changed, 0 insertions, 187 deletions
diff --git a/lib/mpi/mpi-inv.c b/lib/mpi/mpi-inv.c deleted file mode 100644 index 0951f98..0000000 --- a/lib/mpi/mpi-inv.c +++ /dev/null @@ -1,187 +0,0 @@ -/* mpi-inv.c - MPI functions - * Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc. - * - * This file is part of GnuPG. - * - * GnuPG 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 2 of the License, or - * (at your option) any later version. - * - * GnuPG 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 - * along with this program; if not, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA - */ - -#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, const MPI a, const MPI n) -{ - /* Extended Euclid's algorithm (See TAOPC Vol II, 4.5.2, Alg X) - * modified according to Michael Penk's solution for Exercice 35 - * with further enhancement */ - MPI u = NULL, v = NULL; - MPI u1 = NULL, u2 = NULL, u3 = NULL; - MPI v1 = NULL, v2 = NULL, v3 = NULL; - MPI t1 = NULL, t2 = NULL, t3 = NULL; - unsigned k; - int sign; - int odd = 0; - int rc = -ENOMEM; - - if (mpi_copy(&u, a) < 0) - goto cleanup; - if (mpi_copy(&v, n) < 0) - goto cleanup; - - for (k = 0; !mpi_test_bit(u, 0) && !mpi_test_bit(v, 0); k++) { - if (mpi_rshift(u, u, 1) < 0) - goto cleanup; - if (mpi_rshift(v, v, 1) < 0) - goto cleanup; - } - odd = mpi_test_bit(v, 0); - - u1 = mpi_alloc_set_ui(1); - if (!u1) - goto cleanup; - if (!odd) { - u2 = mpi_alloc_set_ui(0); - if (!u2) - goto cleanup; - } - if (mpi_copy(&u3, u) < 0) - goto cleanup; - if (mpi_copy(&v1, v) < 0) - goto cleanup; - if (!odd) { - v2 = mpi_alloc(mpi_get_nlimbs(u)); - if (!v2) - goto cleanup; - if (mpi_sub(v2, u1, u) < 0) - goto cleanup; /* U is used as const 1 */ - } - if (mpi_copy(&v3, v) < 0) - goto cleanup; - if (mpi_test_bit(u, 0)) { /* u is odd */ - t1 = mpi_alloc_set_ui(0); - if (!t1) - goto cleanup; - if (!odd) { - t2 = mpi_alloc_set_ui(1); - if (!t2) - goto cleanup; - t2->sign = 1; - } - if (mpi_copy(&t3, v) < 0) - goto cleanup; - t3->sign = !t3->sign; - goto Y4; - } else { - t1 = mpi_alloc_set_ui(1); - if (!t1) - goto cleanup; - if (!odd) { - t2 = mpi_alloc_set_ui(0); - if (!t2) - goto cleanup; - } - if (mpi_copy(&t3, u) < 0) - goto cleanup; - } - do { - do { - if (!odd) { - if (mpi_test_bit(t1, 0) || mpi_test_bit(t2, 0)) { /* one is odd */ - if (mpi_add(t1, t1, v) < 0) - goto cleanup; - if (mpi_sub(t2, t2, u) < 0) - goto cleanup; - } - if (mpi_rshift(t1, t1, 1) < 0) - goto cleanup; - if (mpi_rshift(t2, t2, 1) < 0) - goto cleanup; - if (mpi_rshift(t3, t3, 1) < 0) - goto cleanup; - } else { - if (mpi_test_bit(t1, 0)) - if (mpi_add(t1, t1, v) < 0) - goto cleanup; - if (mpi_rshift(t1, t1, 1) < 0) - goto cleanup; - if (mpi_rshift(t3, t3, 1) < 0) - goto cleanup; - } -Y4: - ; - } while (!mpi_test_bit(t3, 0)); /* while t3 is even */ - - if (!t3->sign) { - if (mpi_set(u1, t1) < 0) - goto cleanup; - if (!odd) - if (mpi_set(u2, t2) < 0) - goto cleanup; - if (mpi_set(u3, t3) < 0) - goto cleanup; - } else { - if (mpi_sub(v1, v, t1) < 0) - goto cleanup; - sign = u->sign; - u->sign = !u->sign; - if (!odd) - if (mpi_sub(v2, u, t2) < 0) - goto cleanup; - u->sign = sign; - sign = t3->sign; - t3->sign = !t3->sign; - if (mpi_set(v3, t3) < 0) - goto cleanup; - t3->sign = sign; - } - if (mpi_sub(t1, u1, v1) < 0) - goto cleanup; - if (!odd) - if (mpi_sub(t2, u2, v2) < 0) - goto cleanup; - if (mpi_sub(t3, u3, v3) < 0) - goto cleanup; - if (t1->sign) { - if (mpi_add(t1, t1, v) < 0) - goto cleanup; - if (!odd) - if (mpi_sub(t2, t2, u) < 0) - goto cleanup; - } - } while (mpi_cmp_ui(t3, 0)); /* while t3 != 0 */ - /* mpi_lshift( u3, k ); */ - rc = mpi_set(x, u1); - -cleanup: - 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 rc; -} |
