RsaUtils.java

/*
 * Copyright (C) 2016  Matteo Morena
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package mamo.vanillaVotifier.utils;

import org.bouncycastle.util.encoders.Base64;
import org.jetbrains.annotations.NotNull;

import javax.crypto.Cipher;
import java.security.*;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

public class RsaUtils {
	@NotNull
	public static KeyPair genKeyPair() {
		return genKeyPair(2048);
	}

	@NotNull
	public static KeyPair genKeyPair(int keySize) {
		try {
			KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
			keyPairGenerator.initialize(keySize);
			return keyPairGenerator.genKeyPair();
		} catch (NoSuchAlgorithmException e) {
			// Can't happen
			return null;
		}
	}

	@NotNull
	public static PublicKey bytesToPublicKey(@NotNull byte[] bytes) throws InvalidKeySpecException {
		try {
			X509EncodedKeySpec keySpec = new X509EncodedKeySpec(bytes);
			KeyFactory kf = KeyFactory.getInstance("RSA");
			return kf.generatePublic(keySpec);
		} catch (NoSuchAlgorithmException e) {
			// Can't happen
			return null;
		}
	}

	@NotNull
	public static PrivateKey bytesToPrivateKey(@NotNull byte[] bytes) throws InvalidKeySpecException {
		try {
			PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(bytes);
			KeyFactory kf = KeyFactory.getInstance("RSA");
			return kf.generatePrivate(keySpec);
		} catch (NoSuchAlgorithmException e) {
			// Can't happen
			return null;
		}
	}

	@NotNull
	public static Cipher getEncryptCipher(@NotNull PublicKey key) {
		try {
			Cipher cipher;
			cipher = Cipher.getInstance("RSA");
			cipher.init(Cipher.ENCRYPT_MODE, key);
			return cipher;
		} catch (GeneralSecurityException e) { // NoSuchAlgorithmException and NoSuchPaddingException
			// Can't happen
			return null;
		}
	}

	@NotNull
	public static Cipher getDecryptCipher(@NotNull PrivateKey key) {
		try {
			Cipher cipher;
			cipher = Cipher.getInstance("RSA");
			cipher.init(Cipher.DECRYPT_MODE, key);
			return cipher;
		} catch (GeneralSecurityException e) { // NoSuchAlgorithmException and NoSuchPaddingException
			// Can't happen
			return null;
		}
	}

	@NotNull
	public static String keyToString(Key key) {
		return new String(Base64.encode(key.getEncoded()));
	}
}