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DSS Service Provider Interface contains the contract interface shared between the applet and the server-side of DSS.
There is a newer version: 6.0.d4j.2
/**
 * DSS - Digital Signature Services
 * Copyright (C) 2015 European Commission, provided under the CEF programme
 *
 * This file is part of the "DSS - Digital Signature Services" project.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package eu.europa.esig.dss;

import java.security.Key;
import java.security.PublicKey;
import java.security.interfaces.DSAPublicKey;
import java.security.interfaces.ECPublicKey;
import java.security.interfaces.RSAPublicKey;

import org.bouncycastle.jce.provider.JCEECPublicKey;
import org.bouncycastle.jce.spec.ECParameterSpec;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import eu.europa.esig.dss.x509.CertificateToken;
import eu.europa.esig.dss.x509.Token;

public final class DSSPKUtils {

	private static final Logger LOG = LoggerFactory.getLogger(DSSPKUtils.class);

	private DSSPKUtils() {
	}

	/**
	 * This method returns the public algorithm extracted from public key infrastructure. (ex: RSA)
	 *
	 * @param publicKey
	 * @return
	 */
	public static String getPublicKeyEncryptionAlgo(final Key publicKey) {

		String publicKeyAlgorithm = "?";
		// (List of different public key implementations with instanceOf test removed)
		publicKeyAlgorithm = publicKey.getAlgorithm();
		if (!"?".equals(publicKeyAlgorithm)) {

			try {

				publicKeyAlgorithm = EncryptionAlgorithm.forName(publicKeyAlgorithm).getName();
			} catch (DSSException e) {

				LOG.error(e.getMessage());
			}
		}
		return publicKeyAlgorithm;
	}

	/**
	 * This method returns a key length used to sign this token.
	 *
	 * @return
	 */
	public static String getPublicKeySize(Token token) {
		String keyLength = "?";
		PublicKey issuerPublicKey = null;
		if (token.getIssuerToken() != null) {
			issuerPublicKey = token.getIssuerToken().getPublicKey();
		} else if (token.isSelfSigned()) {
			issuerPublicKey = ((CertificateToken) token).getPublicKey();
		}
		if (issuerPublicKey != null) {
			keyLength = String.valueOf(getPublicKeySize(issuerPublicKey));
		}
		return keyLength;
	}

	/**
	 * This method returns the public key size extracted from public key infrastructure.
	 *
	 * @param publicKey
	 * @return
	 */
	public static int getPublicKeySize(final PublicKey publicKey) {

		int publicKeySize = -1;
		if (publicKey instanceof RSAPublicKey) {
			RSAPublicKey rsaPublicKey = (RSAPublicKey) publicKey;
			publicKeySize = rsaPublicKey.getModulus().bitLength();
		} else if (publicKey instanceof JCEECPublicKey) {

			/**
			 * The security of EC systems relies on the size of q, and the size of an EC key refers to the bit-length of
			 * the subgroup size q.
			 */
			final JCEECPublicKey jceecPublicKey = (JCEECPublicKey) publicKey;
			ECParameterSpec spec = jceecPublicKey.getParameters();
			if (spec != null) {

				publicKeySize = spec.getN().bitLength();
			} else {
				// We support the key, but we don't know the key length
				publicKeySize = 0;
				// publicKeySize = jceecPublicKey.getQ().getCurve().getFieldSize();
			}
		} else if (publicKey instanceof ECPublicKey) {

			ECPublicKey ecPublicKey = (ECPublicKey) publicKey;
			java.security.spec.ECParameterSpec spec = ecPublicKey.getParams();
			if (spec != null) {
				publicKeySize = spec.getCurve().getField().getFieldSize();
			} else {
				publicKeySize = 0;
			}
		} else if (publicKey instanceof DSAPublicKey) {
			DSAPublicKey dsaPublicKey = (DSAPublicKey) publicKey;
			publicKeySize = dsaPublicKey.getParams().getP().bitLength();
		} else {

			LOG.error("Unknown public key infrastructure: " + publicKey.getClass().getName());
		}
		return publicKeySize;
	}
}