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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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
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package javax.crypto.spec;

import java.security.spec.AlgorithmParameterSpec;
import java.util.Objects;

/**
 * This class specifies the parameters used with the
 * <a href="https://tools.ietf.org/html/rfc7539"><i>ChaCha20</i></a>
 * algorithm.
 *
 * <p> The parameters consist of a 96-bit nonce and an initial
 * counter value expressed as a 32-bit integer.
 *
 * <p> This class can be used to initialize a {@code Cipher} object that
 * implements the <i>ChaCha20</i> algorithm.
 */
public class ChaCha20ParameterSpec implements AlgorithmParameterSpec {

    // The nonce length is defined by the spec as 96 bits in length.
    private static final int NONCE_LENGTH = 12;

    private final byte[] nonce;
    private final int counter;

    /**
     * Constructs a parameter set for ChaCha20 from the given nonce
     * and counter.
     *
     * @param nonce a 96-bit nonce value
     * @param counter the initial counter value
     *
     * @throws NullPointerException if {@code nonce} is {@code null}
     * @throws IllegalArgumentException if {@code nonce} is not 96-bits
     *      in length.
     */
    public ChaCha20ParameterSpec(byte[] nonce, int counter) {
        this.counter = counter;

        Objects.requireNonNull(nonce, "Nonce must be non-null");
        if (nonce.length == 12) {
            this.nonce = nonce.clone();
        } else {
            throw new IllegalArgumentException(
                    "Nonce must be 96-bits in length");
        }
    }

    /**
     * Returns the nonce value.
     *
     * @return the nonce value.  This method returns a new array each time
     * this method is called.
     */
    public byte[] getNonce() {
        return nonce.clone();
    }

    /**
     * Returns the configured counter value.
     *
     * @return the counter value.
     */
    public int getCounter() {
        return counter;
    }
}