| /* |
| * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code 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 |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, 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. |
| */ |
| |
| /* |
| * @test |
| * @bug 8225603 |
| * @summary Tests whether modInverse() completes in a reasonable time |
| * @run main/othervm ModInvTime |
| */ |
| import java.math.BigInteger; |
| |
| public class ModInvTime { |
| public static void main(String[] args) throws InterruptedException { |
| BigInteger prime = new BigInteger("39402006196394479212279040100143613805079739270465446667946905279627659399113263569398956308152294913554433653942643"); |
| BigInteger s = new BigInteger("9552729729729327851382626410162104591956625415831952158766936536163093322096473638446154604799898109762512409920799"); |
| System.out.format("int length: %d, modulus length: %d%n", |
| s.bitLength(), prime.bitLength()); |
| |
| System.out.println("Computing modular inverse ..."); |
| BigInteger mi = s.modInverse(prime); |
| System.out.format("Modular inverse: %s%n", mi); |
| check(s, prime, mi); |
| |
| BigInteger ns = s.negate(); |
| BigInteger nmi = ns.modInverse(prime); |
| System.out.format("Modular inverse of negation: %s%n", nmi); |
| check(ns, prime, nmi); |
| } |
| |
| public static void check(BigInteger val, BigInteger mod, BigInteger inv) { |
| BigInteger r = inv.multiply(val).remainder(mod); |
| if (r.signum() == -1) |
| r = r.add(mod); |
| if (!r.equals(BigInteger.ONE)) |
| throw new RuntimeException("Numerically incorrect modular inverse"); |
| } |
| } |