RSA算法的非对称加密工具类

import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.Provider;
import java.security.Signature;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.Base64.Decoder;
import java.util.Base64.Encoder;

import org.bouncycastle.jce.provider.BouncyCastleProvider;
/**
 * 非对称加密工具类，用于对数据进行私钥签名和公钥验签
 * 第三方包的maven依赖：
 * <dependency>
    	<groupId>bouncycastle</groupId>
    	<artifactId>bouncycastle-jce-jdk13</artifactId>
    	<version>112</version>
    	<scope>runtime</scope>
    </dependency>
 * @author 大别山人
 */
public class RSAUtil {
	private RSAUtil() {throw new UnsupportedOperationException("工具类不需要实例化");} 
	private static final String ALGORITHM = "RSA";
	private static final String SIGN_TYPE = "SHA256WITHRSA";
	private static final Provider DEFAULT_PROVIDER = new BouncyCastleProvider();
	private static final Decoder BASE64_DECODER = Base64.getDecoder();
	private static final Encoder BASE64_ENCODER = Base64.getEncoder();
	private static KeyFactory keyFactory;
	static {
		try {
			keyFactory = KeyFactory.getInstance(ALGORITHM,DEFAULT_PROVIDER);
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
	}
	/**
	 * 封装密钥对的类
	 * @author i
	 *
	 */
	public static final class RSAKeyPair{
		private String publicKey;
		private String privateKey;
		public String getPublicKey() {
			return publicKey;
		}
		public String getPrivateKey() {
			return privateKey;
		}
		private RSAKeyPair(String publicKey,String privateKey) {
			this.publicKey = publicKey;
			this.privateKey = privateKey;
		}
		@Override
		public String toString() {
			return "RSAKeyPair [publicKey=" + publicKey + ", 
privateKey=" + privateKey + "]";
		}
	}
	/**
	 * 生成base64编码的密钥对
	 * @return
	 * @throws Exception
	 */
	public static final RSAKeyPair createKeyPair() throws Exception {
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(ALGORITHM);
		keyPairGen.initialize(2048);
		KeyPair keyPair = keyPairGen.generateKeyPair();
		return new RSAKeyPair(BASE64_ENCODER.encodeToString(keyPair.getPublic().getEncoded()),BASE64_ENCODER.encodeToString(keyPair.getPrivate().getEncoded()));
	}
	/**
	 * 对指定数据使用私钥进行签名
	 * @param data
	 * @param privateKey
	 * @return
	 */
	public static final String sign(String data,String privateKey) {
		try {
			Signature signature = Signature.getInstance(SIGN_TYPE);
			PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(BASE64_DECODER.decode(privateKey));
			signature.initSign(keyFactory.generatePrivate(keySpec));
			signature.update(toSHA256(data));
			return BASE64_ENCODER.encodeToString(signature.sign());
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}
	/**
	 * 对指定的数据和签名，使用公钥进行验签
	 * @param data
	 * @param publicKey
	 * @param sign
	 * @return
	 */
	public static final boolean signVerify(String data,String publicKey,String sign) {
		try {
			Signature signature = Signature.getInstance(SIGN_TYPE);
			X509EncodedKeySpec keySpec = new X509EncodedKeySpec(BASE64_DECODER.decode(publicKey));
			signature.initVerify(keyFactory.generatePublic(keySpec));
			signature.update(toSHA256(data));
			return signature.verify(BASE64_DECODER.decode(sign));
		} catch (Exception e) {
			e.printStackTrace();
		}
		return false;
	}
	private static final byte[] toSHA256(String data) throws NoSuchAlgorithmException {
		MessageDigest digest = MessageDigest.getInstance("SHA-256");
        digest.update(data.getBytes());
        return digest.digest();
	}
}