RSA加密与解密,SHA1withRSA,生成公钥和私钥

import org.apache.commons.codec.binary.Base64;
import org.apache.commons.lang3.ArrayUtils;

import javax.crypto.Cipher;

import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.SecureRandom;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

public class RSAUtils {

	private static Map keyMap = new HashMap(); 


	/**
	 * 随机生成密钥对
	 * 
	 * @throws NoSuchAlgorithmException
	 */
	public static void genKeyPair() throws NoSuchAlgorithmException {
		// KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
		// 初始化密钥对生成器，密钥大小为96-1024位
		keyPairGen.initialize(1024, new SecureRandom());
		// 生成一个密钥对，保存在keyPair中
		KeyPair keyPair = keyPairGen.generateKeyPair();
		RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); // 得到私钥
		RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); // 得到公钥
		String publicKeyString = new String(Base64.encodeBase64(publicKey
				.getEncoded()));
		// 得到私钥字符串
		String privateKeyString = new String(Base64.encodeBase64((privateKey
				.getEncoded())));
		// 将公钥和私钥保存到Map
		keyMap.put(0, publicKeyString); // 0表示公钥
		keyMap.put(1, privateKeyString); // 1表示私钥
	}

	/**
	 * RSA公钥加密
	 * 
	 * @param str
	 *            加密字符串
	 * @param publicKey
	 *            公钥
	 * @return 密文
	 * @throws Exception
	 *             加密过程中的异常信息
	 */
	public static String encrypt(String str, String publicKey) throws Exception {
		// base64编码的公钥
		byte[] decoded = Base64.decodeBase64(publicKey);
		RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA")
				.generatePublic(new X509EncodedKeySpec(decoded));
		// RSA加密
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.ENCRYPT_MODE, pubKey);
		String outStr = Base64.encodeBase64String(cipher.doFinal(str
				.getBytes("UTF-8")));
		return outStr;
	}

	/**
	 * RSA私钥解密
	 * 
	 * @param str
	 *            加密字符串
	 * @param privateKey
	 *            私钥
	 * @return 铭文
	 * @throws Exception
	 *             解密过程中的异常信息
	 */
	public static String decrypt(String str, String privateKey)
			throws Exception {
		// 64位解码加密后的字符串
		byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
		// base64编码的私钥
		byte[] decoded = Base64.decodeBase64(privateKey);
		RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")
				.generatePrivate(new PKCS8EncodedKeySpec(decoded));
		// RSA解密
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, priKey);
		String outStr = new String(cipher.doFinal(inputByte));
		return outStr;
	}

	/**
	 * 信息公钥加密
	 * 
	 * @param message
	 * @param publicKey
	 * @return
	 * @throws Exception
	 */
	public static byte[] encryptMessage(byte[] message, RSAPublicKey publicKey)
			throws Exception {
		int encodeLength = publicKey.getModulus().bitLength() / 8 - 11;
		byte[] buffers = new byte[] {};
		Cipher cipher = Cipher.getInstance("RSA"); // RSA/ECB/PKCS1Padding
		cipher.init(Cipher.ENCRYPT_MODE, publicKey);
		for (int i = 0; i < message.length; i += encodeLength) {
			byte[] subArray = ArrayUtils.subarray(message, i, i + encodeLength);
			byte[] doFinal = cipher.doFinal(subArray);
			buffers = ArrayUtils.addAll(buffers, doFinal);
		}
		return buffers;
	}

	/**
	 * 取出公钥
	 * 
	 * @param keyBytes
	 *            base64编码后的 byt
	 * @return
	 * @throws Exception
	 */
	public static RSAPublicKey loadPublicKey(byte[] keyBytes) throws Exception {
		KeyFactory keyFactory = KeyFactory.getInstance("RSA");
		X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
		return (RSAPublicKey) keyFactory.generatePublic(spec);
	}

	/**
	 * 取出私钥
	 * 
	 * @param keyBytes
	 *            base64编码后的 byt
	 * @return
	 * @throws Exception
	 */
	public static RSAPrivateKey loadPrivateKey(byte[] keyBytes)
			throws Exception {
		KeyFactory keyFactory = KeyFactory.getInstance("RSA");
		PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);
		return (RSAPrivateKey) keyFactory.generatePrivate(spec);
	}

	/**
	 * 取得SHA1withRSA的密文
	 * 
	 * @param message
	 *            加密的字符串
	 * @param privateKey
	 * @return
	 * @throws Exception
	 */
	public static byte[] SHA1withRSA(byte[] message, RSAPrivateKey privateKey)
			throws Exception {
		Signature signature = Signature.getInstance("SHA1withRSA");
		signature.initSign(privateKey);
		signature.update(message);
		return signature.sign();
	}

}