Returns the value obtained from applying the Euler totient function to an integer value . - Java java.lang

Java examples for java.lang:Math Value

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Description

Returns the value obtained from applying the Euler totient function to an integer value .

Demo Code

/*/*from   w w  w.  j a  v  a  2  s .  c o m*/
 * UniCrypt
 *
 *  UniCrypt(tm) : Cryptographical framework allowing the implementation of cryptographic protocols e.g. e-voting
 *  Copyright (C) 2014 Bern University of Applied Sciences (BFH), Research Institute for
 *  Security in the Information Society (RISIS), E-Voting Group (EVG)
 *  Quellgasse 21, CH-2501 Biel, Switzerland
 *
 *  Licensed under Dual License consisting of:
 *  1. GNU Affero General Public License (AGPL) v3
 *  and
 *  2. Commercial license
 *
 *
 *  1. This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU Affero General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program 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 Affero General Public License for more details.
 *
 *   You should have received a copy of the GNU Affero General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 *  2. Licensees holding valid commercial licenses for UniCrypt may use this file in
 *   accordance with the commercial license agreement provided with the
 *   Software or, alternatively, in accordance with the terms contained in
 *   a written agreement between you and Bern University of Applied Sciences (BFH), Research Institute for
 *   Security in the Information Society (RISIS), E-Voting Group (EVG)
 *   Quellgasse 21, CH-2501 Biel, Switzerland.
 *
 *
 *   For further information contact <e-mail: unicrypt@bfh.ch>
 *
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 * Redistributions of files must retain the above copyright notice.
 */
//package com.java2s;
import java.math.BigInteger;

public class Main {
    /**
     * Returns the value obtained from applying the Euler totient function to an integer {@literal value}.
     * <dt><b>Preconditions:</b></dt>
     * <dd>{@literal primeFactorSet} is the complete set of prime factors of {@literal value}.</dd>
     * <p>
     * @param value          The input value
     * @param primeFactorSet The prime factors of {@literal value}
     * @return the result of applying the Euler totient function to {@literal value}
     * @throws IllegalArgumentException if {@literal value} is {@literal null}, {@literal 0}, or negative
     * @throws IllegalArgumentException if {@literal primeFactorSet} is null or if {@literal primeFactorSet} contains
     *                                  {@literal null}
     * @see MathUtil#arePrimeFactors(BigInteger, BigInteger[])
     * @see MathUtil#removeDuplicates(BigInteger[])
     * @see "Handbook of Applied Cryptography, Fact 2.101 (iii)"
     */
    public static BigInteger eulerFunction(final BigInteger value,
            final BigInteger... primeFactorSet) {
        if (value == null || value.signum() == 0 || value.signum() == -1
                || primeFactorSet == null) {
            throw new IllegalArgumentException();
        }
        BigInteger product1 = BigInteger.ONE;
        BigInteger product2 = BigInteger.ONE;
        for (final BigInteger prime : primeFactorSet) {
            if (prime == null) {
                throw new IllegalArgumentException();
            }
            product1 = product1.multiply(prime);
            product2 = product2.multiply(prime.subtract(BigInteger.ONE));
        }
        return value.multiply(product2).divide(product1);
    }
}

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