RSA相关秘钥问题

清疚 2022-03-14 16:30 207阅读 0赞

package com.ljq.test;
 
 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());
 }
 
 }

**注意：**  
**RSA加密明文最大长度117字节，解密要求密文最大长度为128字节，所以在加密和解密的过程中需要分块进行。**  
**RSA加密对明文的长度是有限制的，如果加密数据过大会抛出如下异常：**

Exception in thread "main" javax.crypto.IllegalBlockSizeException: Data must not be longer than 117 bytes
        at com.sun.crypto.provider.RSACipher.a(DashoA13*..)
        at com.sun.crypto.provider.RSACipher.engineDoFinal(DashoA13*..)
        at javax.crypto.Cipher.doFinal(DashoA13*..)