/**

* EdDSA-Java by str4d
*
* To the extent possible under law, the person who associated CC0 with
* EdDSA-Java has waived all copyright and related or neighboring rights
* to EdDSA-Java.
*
* You should have received a copy of the CC0 legalcode along with this
* work. If not, see <https://creativecommons.org/publicdomain/zero/1.0/>.
*
*/

package net.i2p.crypto.eddsa;

import java.security.InvalidAlgorithmParameterException; import java.security.InvalidParameterException; import java.security.KeyPair; import java.security.KeyPairGeneratorSpi; import java.security.SecureRandom; import java.security.spec.AlgorithmParameterSpec; import java.util.Hashtable;

import net.i2p.crypto.eddsa.spec.EdDSAGenParameterSpec; import net.i2p.crypto.eddsa.spec.EdDSANamedCurveSpec; import net.i2p.crypto.eddsa.spec.EdDSANamedCurveTable; import net.i2p.crypto.eddsa.spec.EdDSAParameterSpec; import net.i2p.crypto.eddsa.spec.EdDSAPrivateKeySpec; import net.i2p.crypto.eddsa.spec.EdDSAPublicKeySpec;

/**

*  Default keysize is 256 (Ed25519)
*/

public final class KeyPairGenerator extends KeyPairGeneratorSpi {

private static final int DEFAULT_KEYSIZE = 256;
private EdDSAParameterSpec edParams;
private SecureRandom random;
private boolean initialized;

private static final Hashtable<Integer, AlgorithmParameterSpec> edParameters;

static {
    edParameters = new Hashtable<Integer, AlgorithmParameterSpec>();

    edParameters.put(Integer.valueOf(256), new EdDSAGenParameterSpec(EdDSANamedCurveTable.ED_25519));
}

public void initialize(int keysize, SecureRandom random) {
    AlgorithmParameterSpec edParams = edParameters.get(Integer.valueOf(keysize));
    if (edParams == null)
        throw new InvalidParameterException("unknown key type.");
    try {
        initialize(edParams, random);
    } catch (InvalidAlgorithmParameterException e) {
        throw new InvalidParameterException("key type not configurable.");
    }
}

@Override
public void initialize(AlgorithmParameterSpec params, SecureRandom random) throws InvalidAlgorithmParameterException {
    if (params instanceof EdDSAParameterSpec) {
        edParams = (EdDSAParameterSpec) params;
    } else if (params instanceof EdDSAGenParameterSpec) {
        edParams = createNamedCurveSpec(((EdDSAGenParameterSpec) params).getName());
    } else
        throw new InvalidAlgorithmParameterException("parameter object not a EdDSAParameterSpec");

    this.random = random;
    initialized = true;
}

public KeyPair generateKeyPair() {
    if (!initialized)
        initialize(DEFAULT_KEYSIZE, new SecureRandom());

    byte[] seed = new byte[edParams.getCurve().getField().getb()/8];
    random.nextBytes(seed);

    EdDSAPrivateKeySpec privKey = new EdDSAPrivateKeySpec(seed, edParams);
    EdDSAPublicKeySpec pubKey = new EdDSAPublicKeySpec(privKey.getA(), edParams);

    return new KeyPair(new EdDSAPublicKey(pubKey), new EdDSAPrivateKey(privKey));
}

/**
 * Create an EdDSANamedCurveSpec from the provided curve name. The current
 * implementation fetches the pre-created curve spec from a table.
 * @param curveName the EdDSA named curve.
 * @return the specification for the named curve.
 * @throws InvalidAlgorithmParameterException if the named curve is unknown.
 */
protected EdDSANamedCurveSpec createNamedCurveSpec(String curveName) throws InvalidAlgorithmParameterException {
    EdDSANamedCurveSpec spec = EdDSANamedCurveTable.getByName(curveName);
    if (spec == null) {
        throw new InvalidAlgorithmParameterException("unknown curve name: " + curveName);
    }
    return spec;
}

}