## OpenJDK / jdk9 / jdk9 / jdk

### view src/jdk.crypto.ec/share/native/libsunec/impl/ec_naf.c @ 17286:65464a307408

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Added tag jdk-9+181 for changeset bd66ea2fdde3

author | prr |
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date | Thu, 03 Aug 2017 18:56:59 +0000 |

parents | b49a0af85821 |

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/* * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved. * Use is subject to license terms. * * This library 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. * * This library 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 library; if not, write to the Free Software Foundation, * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /* ********************************************************************* * * The Original Code is the elliptic curve math library. * * The Initial Developer of the Original Code is * Sun Microsystems, Inc. * Portions created by the Initial Developer are Copyright (C) 2003 * the Initial Developer. All Rights Reserved. * * Contributor(s): * Stephen Fung <fungstep@hotmail.com>, Sun Microsystems Laboratories * *********************************************************************** */ #include "ecl-priv.h" /* Returns 2^e as an integer. This is meant to be used for small powers of * two. */ int ec_twoTo(int e) { int a = 1; int i; for (i = 0; i < e; i++) { a *= 2; } return a; } /* Computes the windowed non-adjacent-form (NAF) of a scalar. Out should * be an array of signed char's to output to, bitsize should be the number * of bits of out, in is the original scalar, and w is the window size. * NAF is discussed in the paper: D. Hankerson, J. Hernandez and A. * Menezes, "Software implementation of elliptic curve cryptography over * binary fields", Proc. CHES 2000. */ mp_err ec_compute_wNAF(signed char *out, int bitsize, const mp_int *in, int w) { mp_int k; mp_err res = MP_OKAY; int i, twowm1, mask; twowm1 = ec_twoTo(w - 1); mask = 2 * twowm1 - 1; MP_DIGITS(&k) = 0; MP_CHECKOK(mp_init_copy(&k, in)); i = 0; /* Compute wNAF form */ while (mp_cmp_z(&k) > 0) { if (mp_isodd(&k)) { out[i] = MP_DIGIT(&k, 0) & mask; if (out[i] >= twowm1) out[i] -= 2 * twowm1; /* Subtract off out[i]. Note mp_sub_d only works with * unsigned digits */ if (out[i] >= 0) { mp_sub_d(&k, out[i], &k); } else { mp_add_d(&k, -(out[i]), &k); } } else { out[i] = 0; } mp_div_2(&k, &k); i++; } /* Zero out the remaining elements of the out array. */ for (; i < bitsize + 1; i++) { out[i] = 0; } CLEANUP: mp_clear(&k); return res; }