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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

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 * accompanied this code).

 *

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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 12-byte 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.

 *

 * @since 11

 */

public final class ChaCha20ParameterSpec implements AlgorithmParameterSpec {

    // The nonce length is defined by the spec as 96 bits (12 bytes) 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 12-byte nonce value

     * @param counter the initial counter value

     *

     * @throws NullPointerException if {@code nonce} is {@code null}

     * @throws IllegalArgumentException if {@code nonce} is not 12 bytes

     *      in length

     */

    public ChaCha20ParameterSpec(byte[] nonce, int counter) {

        this.counter = counter;

        Objects.requireNonNull(nonce, "Nonce must be non-null");

        this.nonce = nonce.clone();

        if (this.nonce.length != NONCE_LENGTH) {

            throw new IllegalArgumentException(

                    "Nonce must be 12-bytes 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;

    }

}