RSA公钥加密 私钥解密

/**
     * 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;
    }

    /**
     * 分段加密，1024的秘钥每次加密最大长度为117
     * @param str
     * @param publicKey
     * @return
     * @throws Exception
     */
    public static String encryptLong( 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/ECB/PKCS1Padding");
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);

        byte[] inputArray = str.getBytes();
        int inputLength = inputArray.length;
        System.out.println("加密字节数：" + inputLength);
        // 最大加密字节数，超出最大字节数需要分组加密
        int MAX_ENCRYPT_BLOCK = 117;
        // 标识
        int offSet = 0;
        byte[] resultBytes = {};
        byte[] cache = {};
        String outStr = "";
        while (inputLength - offSet > 0) {
            if (inputLength - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(inputArray, offSet, MAX_ENCRYPT_BLOCK);
                offSet += MAX_ENCRYPT_BLOCK;
            } else {
                cache = cipher.doFinal(inputArray, offSet, inputLength - offSet);
                offSet = inputLength;
            }
            resultBytes = Arrays.copyOf(resultBytes, resultBytes.length + cache.length);
            System.arraycopy(cache, 0, resultBytes, resultBytes.length - cache.length, cache.length);
        }
        outStr = Base64.encodeBase64String(resultBytes);
        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;
    }

    /**
     * 分段解密，1024的秘钥每次解密最大长度为128
     * @param str
     * @param privateKey
     * @return
     * @throws Exception
     */
    public static String decryptLong(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/ECB/PKCS1Padding");
        cipher.init(Cipher.DECRYPT_MODE, priKey);

        int inputLength = inputByte.length;
        int MAX_DECRYPT_BLOCK = 128;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段解密
        while (inputLength - offSet > 0) {
            if (inputLength - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(inputByte, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(inputByte, offSet, inputLength - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        return new String(decryptedData);
    }