58 lines
2.4 KiB
Java
58 lines
2.4 KiB
Java
/*
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* Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* @test
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* @bug 8225603
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* @summary Tests whether modInverse() completes in a reasonable time
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* @run main/othervm ModInvTime
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*/
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import java.math.BigInteger;
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public class ModInvTime {
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public static void main(String[] args) throws InterruptedException {
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BigInteger prime = new BigInteger("39402006196394479212279040100143613805079739270465446667946905279627659399113263569398956308152294913554433653942643");
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BigInteger s = new BigInteger("9552729729729327851382626410162104591956625415831952158766936536163093322096473638446154604799898109762512409920799");
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System.out.format("int length: %d, modulus length: %d%n",
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s.bitLength(), prime.bitLength());
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System.out.println("Computing modular inverse ...");
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BigInteger mi = s.modInverse(prime);
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System.out.format("Modular inverse: %s%n", mi);
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check(s, prime, mi);
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BigInteger ns = s.negate();
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BigInteger nmi = ns.modInverse(prime);
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System.out.format("Modular inverse of negation: %s%n", nmi);
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check(ns, prime, nmi);
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}
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public static void check(BigInteger val, BigInteger mod, BigInteger inv) {
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BigInteger r = inv.multiply(val).remainder(mod);
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if (r.signum() == -1)
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r = r.add(mod);
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if (!r.equals(BigInteger.ONE))
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throw new RuntimeException("Numerically incorrect modular inverse");
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}
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}
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