RSA加减密工具类

public class RSAUtils {

    /**
     * 加密算法RSA
     */
    public static final String KEY_ALGORITHM = "RSA";

    /**
     * 签名算法
     */
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    /**
     * RSA最大加密明文大小
     */
    private static final int MAX_ENCRYPT_BLOCK = 117;

    /**
     * RSA最大解密密文大小
     */
    private static final int MAX_DECRYPT_BLOCK = 128;


    /**
     * <p>
     * 用私钥对信息生成数字签名
     * </p>
     *
     * @param data       已加密数据
     * @param privateKey 私钥(BASE64编码)
     */
    public static String sign(byte[] data, String privateKey) throws Exception {
        byte[] keyBytes = Base64Fiend.decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(privateK);
        signature.update(data);
        return Base64Fiend.encode(signature.sign());
    }

    /**
     * <p>
     * 公钥加密
     * </p>
     *
     * @param data      源数据
     * @param publicKey 公钥(BASE64编码)
     */
    public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {
        byte[] keyBytes = Base64Fiend.decode(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    // 公钥 (服务端)
    private static final String publicKey = "*********************";

    //私钥 (客户端)
    private static final String privateKeyClient = "*****************************************";


    /**
     * 公钥加密
     * 返回随机数和密文
     */
    public static Map<String, String> actRsaPubkeyEncryMap(String src) throws Exception {
        /*生成随机数,随机数作为aes秘钥加密，随机数rsa，aes报文+rsa报文*/
        String randomNumber = RandomStringUtils.randomString(16);
        byte[] encryByte = RSAUtils.encryptByPublicKey(randomNumber.getBytes(), publicKey);
        String resData = Base64Fiend.encode(encryByte);
        String aesData = AESUtil.encrypt(src, randomNumber);
        Map<String, String> map = new HashMap<>();
        map.put("content", aesData + resData);
        map.put("random", randomNumber);
        return map;
    }

    /**
     * 带签名的使用公钥加密
     *
     */
    public static Map<String, String> actRsaPubkeyEncrySignMap(String content) throws Exception {
        // 对参数MD5加密生成摘要
        String digest = Md5Encrypt.EncoderByMd5(content);
        // 使用客户端私钥生成签名
        String sign = sign(digest.getBytes(), privateKeyClient);
        return actRsaPubkeyEncryMap(content + sign);
    }

    /**
     * 公钥解密
     */
    public static String actResPubkeyDes(String data, String random) {
        return AESUtil.decrypt(data, random);
    }



}