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/*
 * Copyright 2023 okome.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.siisise.security.digest;

import java.nio.charset.StandardCharsets;
import net.siisise.io.Packet;

/**
 * NIST SP 800-185 cSHAKE.
 * ビット列用だがバイト列で使う.
 *
 */
public class cSHAKE extends Keccak {

    /**
     * cSHAKE.
     * N, Sが空の場合はSHAKEと同じ
     *
     * @param c セキュリティ強度 128 または 256
     * @param d 出力長 bit
     * @param N 関数名のビット文字列
     * @param S 任意の文字列
     */
    public cSHAKE(int c, int d, String N, String S) {
        super("cSHAKE" + c + "(" + d + ")", 2 * c, d, (((N != null && !N.isEmpty()) || (S != null && !S.isEmpty())) ? (byte) 0x04 : (byte) 0x1f));
        if (N == null) {
            N = "";
        }
        if (S == null) {
            S = "";
        }
        if (!N.isEmpty() || !S.isEmpty()) {
            Packet p;
            p = SHA3Derived.encode_string(N.getBytes(StandardCharsets.UTF_8));
            p.write(SHA3Derived.encode_string(S.getBytes(StandardCharsets.UTF_8)));
            byte[] x = SHA3Derived.bytepad(p, getBitBlockLength() / 8);
            // KeccakのengineUpdate を呼びたいが継承されることもあるのでsuper.をつけておく
            super.engineUpdate(x, 0, x.length);
        }
    }
}