JcaLMSKeyPairGenerator.java

/*
 * GordianKnot: Security Suite
 * Copyright 2026. Tony Washer
 *
 * 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 io.github.tonywasher.joceanus.gordianknot.impl.jca.keypair;

import io.github.tonywasher.joceanus.gordianknot.api.base.GordianException;
import io.github.tonywasher.joceanus.gordianknot.api.keypair.spec.GordianKeyPairSpec;
import io.github.tonywasher.joceanus.gordianknot.impl.core.base.GordianBaseFactory;
import io.github.tonywasher.joceanus.gordianknot.impl.core.exc.GordianCryptoException;
import io.github.tonywasher.joceanus.gordianknot.impl.core.spec.keypair.GordianCoreKeyPairSpec;
import io.github.tonywasher.joceanus.gordianknot.impl.core.spec.keypair.GordianCoreLMSSpec;
import io.github.tonywasher.joceanus.gordianknot.impl.jca.keypair.JcaKeyPairGenerator.JcaStateAwareKeyPairGenerator;
import org.bouncycastle.pqc.crypto.lms.LMSParameters;
import org.bouncycastle.pqc.jcajce.spec.LMSHSSKeyGenParameterSpec;
import org.bouncycastle.pqc.jcajce.spec.LMSKeyGenParameterSpec;

import java.security.InvalidAlgorithmParameterException;
import java.security.spec.AlgorithmParameterSpec;
import java.util.Arrays;

/**
 * Jca LMS KeyPair generator.
 */
public class JcaLMSKeyPairGenerator
        extends JcaStateAwareKeyPairGenerator {
    /**
     * Constructor.
     *
     * @param pFactory the Security Factory
     * @param pKeySpec the keySpec
     * @throws GordianException on error
     */
    JcaLMSKeyPairGenerator(final GordianBaseFactory pFactory,
                           final GordianKeyPairSpec pKeySpec) throws GordianException {
        /* initialize underlying class */
        super(pFactory, pKeySpec);

        /* Create and initialize the generator */
        final String myJavaType = pKeySpec.getKeyPairType().toString();
        createFactories(myJavaType, true);

        /* Protect against exceptions */
        try {
            final GordianCoreKeyPairSpec myKeySpec = (GordianCoreKeyPairSpec) pKeySpec;
            final AlgorithmParameterSpec myParms = deriveParameters(myKeySpec.getLMSSpec());
            getGenerator().initialize(myParms, getRandom());

        } catch (InvalidAlgorithmParameterException e) {
            throw new GordianCryptoException("Failed to initialize generator", e);
        }
    }

    /**
     * Derive the parameters.
     *
     * @param pKeySpec the keySPec
     * @return the parameters.
     */
    private static LMSHSSKeyGenParameterSpec deriveParameters(final GordianCoreLMSSpec pKeySpec) {
        /* Generate and return the keyPair */
        final LMSKeyGenParameterSpec[] myParams = new LMSKeyGenParameterSpec[pKeySpec.getTreeDepth()];
        final LMSParameters myParms = pKeySpec.getParameters();
        final LMSKeyGenParameterSpec myKeyGen = new LMSKeyGenParameterSpec(myParms.getLMSigParam(), myParms.getLMOTSParam());
        Arrays.fill(myParams, myKeyGen);
        return new LMSHSSKeyGenParameterSpec(myParams);
    }
}