RSA 加密 & 解密

import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
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;

import javax.crypto.Cipher;

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

public class RSAUtils {
    /** 非对称密钥算法 */
    public static final String KEY_ALGORITHM = "RSA";
    /** 密钥长度，DH算法的默认密钥长度是1024 密钥长度必须是64的倍数，在512到65536位之间  */
    private static final int KEY_SIZE = 512;
    /** 公钥 */
    private static final String PUBLIC_KEY = "RSAPublicKey";
    /** 私钥 */
    private static final String PRIVATE_KEY = "RSAPrivateKey";
    
    public static void main(String[] args) throws Exception {
        //初始化密钥,生成密钥对
        Map<String, Object> keyMap = RSAUtils.initKey();
        //公钥
        byte[] publicKey = RSAUtils.getPublicKey(keyMap);
        System.out.println("公钥：" + Base64.encodeBase64String(publicKey));
        //私钥
        byte[] privateKey = RSAUtils.getPrivateKey(keyMap);
        System.out.println("私钥=："+ Base64.encodeBase64String(privateKey));
        //待加密数据
        String str1 = "RSA私钥加密公钥解密";
        System.out.println("------step1------私钥加密------");
        System.out.println("私钥加密原文:" + str1);
        //私钥加密
        byte[] code1 = RSAUtils.encryptByPrivateKey(str1.getBytes(), privateKey);
        System.out.println("私钥加密后的数据：" + Base64.encodeBase64String(code1));
        //公钥解密
        System.out.println("------step2------公钥解密------");
        byte[] decode1 = RSAUtils.decryptByPublicKey(code1, publicKey);
        System.out.println("公钥解密后的数据：" + new String(decode1));
        System.out.println("------step3------公钥加密------");
        String str2 = "RSA公钥加密私钥解密";
        System.out.println("公钥加密原文:" + str2);
        //乙方使用公钥对数据进行加密
        byte[] code2 = RSAUtils.encryptByPublicKey(str2.getBytes(), publicKey);
        System.out.println("公钥加密后的数据：" + Base64.encodeBase64String(code2));
        System.out.println("------step4------私钥解密------");
        //甲方使用私钥对数据进行解密
        byte[] decode2 = RSAUtils.decryptByPrivateKey(code2, privateKey);
        System.out.println("私钥解密后的数据：" + new String(decode2));
    }
    
    /** 初始化密钥对   */
    public static Map<String, Object> initKey() throws Exception {
        //实例化密钥生成器
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        //初始化密钥生成器
        keyPairGenerator.initialize(KEY_SIZE);
        //生成密钥对
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        //甲方公钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        //甲方私钥
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        //将密钥存储在map中
        Map<String, Object> keyMap = new HashMap<String, Object>();
        keyMap.put(PUBLIC_KEY, publicKey);
        keyMap.put(PRIVATE_KEY, privateKey);
        return keyMap;
    }

    /**
     * 私钥加密
     * @param data 待加密数据
     * @param key       密钥
     * @return byte[] 加密数据
     */
    public static byte[] encryptByPrivateKey(byte[] data, byte[] key) throws Exception {
        //实例化密钥工厂
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        //密钥材料转换
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(key);
        //生成私钥
        PrivateKey privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
        //数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);
        return cipher.doFinal(data);
    }

    /**
     * 公钥加密
     * @param data 待加密数据
     * @param key       密钥
     * @return byte[] 加密数据
     */
    public static byte[] encryptByPublicKey(byte[] data, byte[] key) throws Exception {
        //实例化密钥工厂
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        //密钥材料转换
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(key);
        //生成公钥
        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
        //数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        return cipher.doFinal(data);
    }

    /**
     * 私钥解密
     * @param data 待解密数据
     * @param key  密钥
     * @return byte[] 解密数据
     */
    public static byte[] decryptByPrivateKey(byte[] data, byte[] key) throws Exception {
        //实例化密钥工厂
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        //密钥材料转换
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(key);
        //生成私钥
        PrivateKey privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
        //数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return cipher.doFinal(data);
    }

    /**
     * 公钥解密
     * @param data 待解密数据
     * @param key  密钥
     * @return byte[] 解密数据
     */
    public static byte[] decryptByPublicKey(byte[] data, byte[] key) throws Exception {
        //实例化密钥工厂
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        //密钥材料转换
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(key);
        //产生公钥
        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
        //数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, pubKey);
        return cipher.doFinal(data);
    }

    /**
     * 取得私钥
     * @param keyMap 密钥map
     * @return byte[] 私钥
     */
    public static byte[] getPrivateKey(Map<String, Object> keyMap) {
        Key key = (Key) keyMap.get(PRIVATE_KEY);
        return key.getEncoded();
    }

    /**
     * 取得公钥
     * @param keyMap 密钥map
     * @return byte[] 公钥
     */
    public static byte[] getPublicKey(Map<String, Object> keyMap) throws Exception {
        Key key = (Key) keyMap.get(PUBLIC_KEY);
        return key.getEncoded();
    }
}