RSA非对称密钥加解密使用示例

清疚 2022-06-04 09:52 356阅读 0赞

**一、简介：**

RSA加密算法是最常用的非对称加密算法，CFCA在证书服务中离不了它。RSA是第一个比较完善的公开密钥算法，它既能用于加密，也能用于数字签名。这个算法经受住了多年深入的密码分析，虽然密码分析者既不能证明也不能否定RSA的安全性，但这恰恰说明该算法有一定的可信性，目前它已经成为最流行的公开密钥算法。  
**二、RSA的公钥、私钥的组成，以及加密、解密的公式**  
　　  
**三、使用方式：**  
　　① 假设A、B机器进行通信，已A机器为主；  
　　② A首先需要用自己的私钥为发送请求数据签名，并将公钥一同发送给B；  
　　③ B收到数据后，需要用A发送的公钥进行验证，已确保收到的数据是未经篡改的；  
　　④ B验签通过后，处理逻辑，并把处理结果返回，返回数据需要用A发送的公钥进行加密（公钥加密后，只能用配对的私钥解密）；  
　　⑤ A收到B返回的数据，使用私钥解密，至此，一次数据交互完成。  
　　  
**四、代码示例：**  
**1、第一步获取私钥，为签名做准备。**

/** * 读取私钥 返回PrivateKey * @param path 包含私钥的证书路径 * @param password 私钥证书密码 * @return 返回私钥PrivateKey * @throws KeyStoreException * @throws NoSuchAlgorithmException * @throws CertificateException * @throws IOException * @throws UnrecoverableKeyException */
 private static PrivateKey getPrivateKey(String path,String password)
 throws KeyStoreException, NoSuchAlgorithmException, CertificateException,
 IOException, UnrecoverableKeyException {
 KeyStore ks = KeyStore.getInstance("PKCS12");
 FileInputStream fis = new FileInputStream(path);
 char[] nPassword = null;
 if ((password == null) || password.trim().equals("")) {
 nPassword = null;
 } else {
 nPassword = password.toCharArray();
 }
 ks.load(fis, nPassword);
 fis.close();
 Enumeration<String> en = ks.aliases();
 String keyAlias = null;
 if (en.hasMoreElements()) {
 keyAlias = (String) en.nextElement();
 }
 
 return (PrivateKey) ks.getKey(keyAlias, nPassword);
 }

**2、签名示例：通过第一步得到的私钥，进行签名操作，具体请看以下代码：**

/** * 私钥签名： 签名方法如下：BASE64(RSA(MD5(src),privatekey))，其中src为需要签名的字符串， privatekey是商户的CFCA证书私钥。 * @param plainText 待签名字符串 * @param path 签名私钥路径 * @param password 签名私钥密码 * @return 返回签名后的字符串 * @throws Exception */
        public static String sign(String plainText,String path,String password)
                throws Exception  {
            /* * MD5加密 */
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            md5.update(plainText.getBytes("utf-8"));
            byte[] digestBytes = md5.digest();
            /* * 用私钥进行签名 RSA * Cipher负责完成加密或解密工作，基于RSA */
            Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
            //ENCRYPT_MODE表示为加密模式
            cipher.init(Cipher.ENCRYPT_MODE, getPrivateKey(path, password));
            //加密
            byte[] rsaBytes = cipher.doFinal(digestBytes);
            //Base64编码
            return Base64.byteArrayToBase64(rsaBytes);

**3、B收到数据后，需要使用A提供的公钥信息进行验签，此处使用公钥的N、E进行验签首先通过公钥N、E得到公钥PublicKey，如下：**

/** * 根据公钥n、e生成公钥 * @param modulus 公钥n串 * @param publicExponent 公钥e串 * @return 返回公钥PublicKey * @throws Exception */
        public static PublicKey getPublickKey(String modulus, String publicExponent)
                throws Exception {
            KeySpec publicKeySpec = new RSAPublicKeySpec(
                    new BigInteger(modulus, 16), new BigInteger(publicExponent, 16));
            KeyFactory factory = KeyFactory.getInstance("RSA");
            PublicKey publicKey = factory.generatePublic(publicKeySpec);
            return publicKey;
        }

**得到公钥PublicKey后，再去验证签名，代码如下：**

/** * 用公钥证书进行验签 * @param message 签名之前的原文 * @param cipherText 签名 * @param pubKeyn 公钥n串 * @param pubKeye 公钥e串 * @return boolean 验签成功为true,失败为false * @throws Exception */
        public static boolean verify(String message, String cipherText,String pubKeyn,
                String pubKeye) throws Exception {
            Cipher c4 = Cipher.getInstance("RSA/ECB/PKCS1Padding");
            // 根据密钥，对Cipher对象进行初始化,DECRYPT_MODE表示解密模式
            c4.init(Cipher.DECRYPT_MODE, getPublickKey(pubKeyn,pubKeye));
            // 解密
            byte[] desDecTextBytes = c4.doFinal(Base64.base64ToByteArray(cipherText));
            // 得到前置对原文进行的MD5
            String md5Digest1 = Base64.byteArrayToBase64(desDecTextBytes);
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            md5.update(message.getBytes("utf-8"));
            byte[] digestBytes = md5.digest();
            // 得到商户对原文进行的MD5
            String md5Digest2 = Base64.byteArrayToBase64(digestBytes);
            // 验证签名
            if (md5Digest1.equals(md5Digest2)) {
                return true;
            } else {
                return false;
            }
        }

**至此，签名验签已经完毕**  
　  
**4、提供一个从.cer文件读取公钥的方法：**

/** * 读取公钥cer * @param path .cer文件的路径 如：c:/abc.cer * @return base64后的公钥串 * @throws IOException * @throws CertificateException */
        public static String getPublicKey(String path) throws IOException,
        CertificateException{
            InputStream inStream = new FileInputStream(path);
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int ch;
            String res = "";
            while ((ch = inStream.read()) != -1) {
                out.write(ch);
            }
            byte[] result = out.toByteArray();
            res = Base64.byteArrayToBase64(result);
            return res;
        }

#### 代码封装 ####

package utils;
 import java.io.ByteArrayOutputStream;
 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.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;
 
 import javax.crypto.Cipher;
 
 /** * * RSA公钥/私钥/签名工具包 * * * 罗纳德·李维斯特（Ron [R]ivest）、阿迪·萨莫尔（Adi [S]hamir）和伦纳德·阿德曼（Leonard [A]dleman） * * * 字符串格式的密钥在未在特殊说明情况下都为BASE64编码格式 * 由于非对称加密速度极其缓慢，一般文件不使用它来加密而是使用对称加密， * 非对称加密算法可以用来对对称加密的密钥加密，这样保证密钥的安全也就保证了数据的安全 * * * @author IceWee * @date 2012-4-26 * @version 1.0 */
 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";
 
 /** * 获取公钥的key */
 private static final String PUBLIC_KEY = "RSAPublicKey";
 
 /** * 获取私钥的key */
 private static final String PRIVATE_KEY = "RSAPrivateKey";
 
 /** * 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;
 
 /** * * 生成密钥对(公钥和私钥) * * * @return * @throws Exception */
 public static Map<String, Object> genKeyPair() throws Exception {
 KeyPairGenerator keyPairGen = KeyPairGenerator
 .getInstance(KEY_ALGORITHM);
 keyPairGen.initialize(1024);
 KeyPair keyPair = keyPairGen.generateKeyPair();
 RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
 RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
 Map<String, Object> keyMap = new HashMap<String, Object>(2);
 keyMap.put(PUBLIC_KEY, publicKey);
 keyMap.put(PRIVATE_KEY, privateKey);
 return keyMap;
 }
 
 /** * * 用私钥对信息生成数字签名 * * * @param data * 已加密数据 * @param privateKey * 私钥(BASE64编码) * * @return * @throws Exception */
 public static String sign(byte[] data, String privateKey) throws Exception {
 byte[] keyBytes = Base64Utils.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 Base64Utils.encode(signature.sign());
 }
 
 /** * * 校验数字签名 * * * @param data * 已加密数据 * @param publicKey * 公钥(BASE64编码) * @param sign * 数字签名 * * @return * @throws Exception * */
 public static boolean verify(byte[] data, String publicKey, String sign)
 throws Exception {
 byte[] keyBytes = Base64Utils.decode(publicKey);
 X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
 KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
 PublicKey publicK = keyFactory.generatePublic(keySpec);
 Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
 signature.initVerify(publicK);
 signature.update(data);
 return signature.verify(Base64Utils.decode(sign));
 }
 
 /** * * 私钥解密 * * * @param encryptedData * 已加密数据 * @param privateKey * 私钥(BASE64编码) * @return * @throws Exception */
 public static byte[] decryptByPrivateKey(byte[] encryptedData,
 String privateKey) throws Exception {
 byte[] keyBytes = Base64Utils.decode(privateKey);
 PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
 KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
 Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
 Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
 cipher.init(Cipher.DECRYPT_MODE, privateK);
 int inputLen = encryptedData.length;
 ByteArrayOutputStream out = new ByteArrayOutputStream();
 int offSet = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段解密
 while (inputLen - offSet > 0) {
 if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
 cache = cipher
 .doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
 } else {
 cache = cipher
 .doFinal(encryptedData, offSet, inputLen - offSet);
 }
 out.write(cache, 0, cache.length);
 i++;
 offSet = i * MAX_DECRYPT_BLOCK;
 }
 byte[] decryptedData = out.toByteArray();
 out.close();
 return decryptedData;
 }
 
 /** * * 公钥解密 * * * @param encryptedData * 已加密数据 * @param publicKey * 公钥(BASE64编码) * @return * @throws Exception */
 public static byte[] decryptByPublicKey(byte[] encryptedData,
 String publicKey) throws Exception {
 byte[] keyBytes = Base64Utils.decode(publicKey);
 X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
 KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
 Key publicK = keyFactory.generatePublic(x509KeySpec);
 Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
 cipher.init(Cipher.DECRYPT_MODE, publicK);
 int inputLen = encryptedData.length;
 ByteArrayOutputStream out = new ByteArrayOutputStream();
 int offSet = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段解密
 while (inputLen - offSet > 0) {
 if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
 cache = cipher
 .doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
 } else {
 cache = cipher
 .doFinal(encryptedData, offSet, inputLen - offSet);
 }
 out.write(cache, 0, cache.length);
 i++;
 offSet = i * MAX_DECRYPT_BLOCK;
 }
 byte[] decryptedData = out.toByteArray();
 out.close();
 return decryptedData;
 }
 
 /** * * 公钥加密 * * * @param data * 源数据 * @param publicKey * 公钥(BASE64编码) * @return * @throws Exception */
 public static byte[] encryptByPublicKey(byte[] data, String publicKey)
 throws Exception {
 byte[] keyBytes = Base64Utils.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;
 }
 
 /** * * 私钥加密 * * * @param data * 源数据 * @param privateKey * 私钥(BASE64编码) * @return * @throws Exception */
 public static byte[] encryptByPrivateKey(byte[] data, String privateKey)
 throws Exception {
 byte[] keyBytes = Base64Utils.decode(privateKey);
 PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
 KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
 Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
 Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
 cipher.init(Cipher.ENCRYPT_MODE, privateK);
 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;
 }
 
 /** * * 获取私钥 * * * @param keyMap * 密钥对 * @return * @throws Exception */
 public static String getPrivateKey(Map<String, Object> keyMap)
 throws Exception {
 Key key = (Key) keyMap.get(PRIVATE_KEY);
 return Base64Utils.encode(key.getEncoded());
 }
 
 /** * * 获取公钥 * * * @param keyMap * 密钥对 * @return * @throws Exception */
 public static String getPublicKey(Map<String, Object> keyMap)
 throws Exception {
 Key key = (Key) keyMap.get(PUBLIC_KEY);
 return Base64Utils.encode(key.getEncoded());
 }
 
 }

**Base64Utils文件**

package utils;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.InputStream;
 import java.io.OutputStream;
 import com.sun.org.apache.xml.internal.security.utils.Base64; 
 /** * * BASE64编码解码工具包 * * * 依赖javabase64-1.3.1.jar * * * @author IceWee * @date 2012-5-19 * @version 1.0 */
 public class Base64Utils { 
 
 /** * 文件读取缓冲区大小 */
 private static final int CACHE_SIZE = 1024;
 
 /** * * BASE64字符串解码为二进制数据 * * * @param base64 * @return * @throws Exception */
 public static byte[] decode(String base64) throws Exception {
 return Base64.decode(base64.getBytes());
 }
 
 /** * * 二进制数据编码为BASE64字符串 * * * @param bytes * @return * @throws Exception */
 public static String encode(byte[] bytes) throws Exception {
 return new String(Base64.encode(bytes));
 }
 
 /** * * 将文件编码为BASE64字符串 * * * 大文件慎用，可能会导致内存溢出 * * * @param filePath 文件绝对路径 * @return * @throws Exception */
 public static String encodeFile(String filePath) throws Exception {
 byte[] bytes = fileToByte(filePath);
 return encode(bytes);
 }
 
 /** * * BASE64字符串转回文件 * * * @param filePath 文件绝对路径 * @param base64 编码字符串 * @throws Exception */
 public static void decodeToFile(String filePath, String base64) throws Exception {
 byte[] bytes = decode(base64);
 byteArrayToFile(bytes, filePath);
 }
 
 /** * * 文件转换为二进制数组 * * * @param filePath 文件路径 * @return * @throws Exception */
 public static byte[] fileToByte(String filePath) throws Exception {
 byte[] data = new byte[0];
 File file = new File(filePath);
 if (file.exists()) {
 FileInputStream in = new FileInputStream(file);
 ByteArrayOutputStream out = new ByteArrayOutputStream(2048);
 byte[] cache = new byte[CACHE_SIZE];
 int nRead = 0;
 while ((nRead = in.read(cache)) != -1) {
 out.write(cache, 0, nRead);
 out.flush();
 }
 out.close();
 in.close();
 data = out.toByteArray();
 }
 return data;
 }
 
 /** * * 二进制数据写文件 * * * @param bytes 二进制数据 * @param filePath 文件生成目录 */
 public static void byteArrayToFile(byte[] bytes, String filePath) throws Exception {
 InputStream in = new ByteArrayInputStream(bytes); 
 File destFile = new File(filePath);
 if (!destFile.getParentFile().exists()) {
 destFile.getParentFile().mkdirs();
 }
 destFile.createNewFile();
 OutputStream out = new FileOutputStream(destFile);
 byte[] cache = new byte[CACHE_SIZE];
 int nRead = 0;
 while ((nRead = in.read(cache)) != -1) { 
 out.write(cache, 0, nRead);
 out.flush();
 }
 out.close();
 in.close();
 }
 
 
 }

**测试用例：**

package util;
 
 
 import java.util.Map;
 
 import RSAUtils;
 
 public class RSATester {
 
 static String publicKey;
 static String privateKey;
 
 static {
 try {
 Map<String, Object> keyMap = RSAUtils.genKeyPair();
 publicKey = RSAUtils.getPublicKey(keyMap);
 privateKey = RSAUtils.getPrivateKey(keyMap);
 System.err.println("公钥: \n\r" + publicKey);
 System.err.println("私钥： \n\r" + privateKey);
 } catch (Exception e) {
 e.printStackTrace();
 }
 }
 
 public static void main(String[] args) throws Exception {
 test();
 testSign();
 }
 
 static void test() throws Exception {
 System.err.println("公钥加密——私钥解密");
 String source = "这是一行没有任何意义的文字，你看完了等于没看，不是吗？";
 System.out.println("\r加密前文字：\r\n" + source);
 byte[] data = source.getBytes();
 byte[] encodedData = RSAUtils.encryptByPublicKey(data, publicKey);
 System.out.println("加密后文字：\r\n" + new String(encodedData));
 byte[] decodedData = RSAUtils.decryptByPrivateKey(encodedData, privateKey);
 String target = new String(decodedData);
 System.out.println("解密后文字: \r\n" + target);
 }
 
 static void testSign() throws Exception {
 System.err.println("私钥加密——公钥解密");
 String source = "这是一行测试RSA数字签名的无意义文字";
 System.out.println("原文字：\r\n" + source);
 byte[] data = source.getBytes();
 byte[] encodedData = RSAUtils.encryptByPrivateKey(data, privateKey);
 System.out.println("加密后：\r\n" + new String(encodedData));
 byte[] decodedData = RSAUtils.decryptByPublicKey(encodedData, publicKey);
 String target = new String(decodedData);
 System.out.println("解密后: \r\n" + target);
 System.err.println("私钥签名——公钥验证签名");
 String sign = RSAUtils.sign(encodedData, privateKey);
 System.err.println("签名:\r" + sign);
 boolean status = RSAUtils.verify(encodedData, publicKey, sign);
 System.err.println("验证结果:\r" + status);
 }
 
 }

**生成RSA密钥、保存到文件、从文件读取、加密、解密等操作**

import java.security.Key; 
 import java.security.KeyFactory; 
 import java.security.KeyPair; 
 import java.security.KeyPairGenerator; 
 import java.security.NoSuchAlgorithmException; 
 import java.security.PrivateKey; 
 import java.security.PublicKey; 
 import java.security.SecureRandom; 
 import java.security.interfaces.RSAPrivateKey; 
 import java.security.interfaces.RSAPublicKey; 
 import java.security.spec.InvalidKeySpecException; 
 import java.security.spec.PKCS8EncodedKeySpec; 
 import java.security.spec.X509EncodedKeySpec; 
 import javax.crypto.Cipher; 
 import org.apache.commons.configuration.ConfigurationException; 
 import org.apache.commons.configuration.PropertiesConfiguration; 
 import org.bouncycastle.jce.provider.BouncyCastleProvider; 
 
 public class RSATest { 
 
 public static void main(String[] args) { 
 try { 
 RSATest encrypt = new RSATest(); 
 String encryptText = "encryptText"; 
 
 // Generate keys 
 KeyPair keyPair = encrypt.generateKey(); 
 RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); 
 RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); 
 
 byte[] e = encrypt.encrypt(publicKey, encryptText.getBytes()); 
 byte[] de = encrypt.decrypt(privateKey, e); 
 System.out.println(toHexString(e)); 
 System.out.println(toHexString(de)); 
 } catch (Exception e) { 
 e.printStackTrace(); 
 } 
 } 
 
 public KeyPair generateKey() throws NoSuchAlgorithmException { 
 KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA"); 
 keyPairGen.initialize(1024, new SecureRandom()); 
 
 KeyPair keyPair = keyPairGen.generateKeyPair(); 
 return keyPair; 
 } 
 
 public void saveKey(KeyPair keyPair, String publicKeyFile, 
 String privateKeyFile) throws ConfigurationException { 
 PublicKey pubkey = keyPair.getPublic(); 
 PrivateKey prikey = keyPair.getPrivate(); 
 
 // save public key 
 PropertiesConfiguration publicConfig = new PropertiesConfiguration( 
 publicKeyFile); 
 publicConfig.setProperty("PULIICKEY", toHexString(pubkey.getEncoded())); 
 publicConfig.save(); 
 
 // save private key 
 PropertiesConfiguration privateConfig = new PropertiesConfiguration( 
 privateKeyFile); 
 privateConfig.setProperty("PRIVATEKEY", 
 toHexString(prikey.getEncoded())); 
 privateConfig.save(); 
 } 
 
 /** * @param filename * @param type： * 1-public 0-private * @return * @throws ConfigurationException * @throws NoSuchAlgorithmException * @throws InvalidKeySpecException */ 
 public Key loadKey(String filename, int type) 
 throws ConfigurationException, NoSuchAlgorithmException, 
 InvalidKeySpecException { 
 PropertiesConfiguration config = new PropertiesConfiguration(filename); 
 KeyFactory keyFactory = KeyFactory.getInstance("RSA", 
 new BouncyCastleProvider()); 
 
 if (type == 0) { 
 // privateKey 
 String privateKeyValue = config.getString("PULIICKEY"); 
 PKCS8EncodedKeySpec priPKCS8 = new PKCS8EncodedKeySpec( 
 toBytes(privateKeyValue)); 
 PrivateKey privateKey = keyFactory.generatePrivate(priPKCS8); 
 return privateKey; 
 
 } else { 
 // publicKey 
 String privateKeyValue = config.getString("PRIVATEKEY"); 
 X509EncodedKeySpec bobPubKeySpec = new X509EncodedKeySpec( 
 toBytes(privateKeyValue)); 
 PublicKey publicKey = keyFactory.generatePublic(bobPubKeySpec); 
 return publicKey; 
 } 
 } 
 
 /** * Encrypt String. * * @return byte[] */ 
 protected byte[] encrypt(RSAPublicKey publicKey, byte[] data) { 
 if (publicKey != null) { 
 try { 
 Cipher cipher = Cipher.getInstance("RSA", 
 new BouncyCastleProvider()); 
 cipher.init(Cipher.ENCRYPT_MODE, publicKey); 
 return cipher.doFinal(data); 
 } catch (Exception e) { 
 e.printStackTrace(); 
 } 
 } 
 return null; 
 } 
 
 /** * Basic decrypt method * * @return byte[] */ 
 protected byte[] decrypt(RSAPrivateKey privateKey, byte[] raw) { 
 if (privateKey != null) { 
 try { 
 Cipher cipher = Cipher.getInstance("RSA", 
 new BouncyCastleProvider()); 
 cipher.init(Cipher.DECRYPT_MODE, privateKey); 
 return cipher.doFinal(raw); 
 } catch (Exception e) { 
 e.printStackTrace(); 
 } 
 } 
 
 return null; 
 } 
 
 public static String toHexString(byte[] b) { 
 StringBuilder sb = new StringBuilder(b.length * 2); 
 for (int i = 0; i < b.length; i++) { 
 sb.append(HEXCHAR[(b[i] & 0xf0) >>> 4]); 
 sb.append(HEXCHAR[b[i] & 0x0f]); 
 } 
 return sb.toString(); 
 } 
 
 public static final byte[] toBytes(String s) { 
 byte[] bytes; 
 bytes = new byte[s.length() / 2]; 
 for (int i = 0; i < bytes.length; i++) { 
 bytes[i] = (byte) Integer.parseInt(s.substring(2 * i, 2 * i + 2), 
 16); 
 } 
 return bytes; 
 } 
 
 private static char[] HEXCHAR = { '0', '1', '2', '3', '4', '5', '6', '7', 
 '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; 
 
 }

[推荐阅读][Link 1]

[Link 1]: http://blog.csdn.net/keda8997110/article/details/16823361