密码学（二）—RSA后端加解密java实现
理论和实践差距还是很大的，在实现的过程中出现过很多问题。RSA后端加解密实验过很多次，不管是编码问题（加密数据大小有长度限制），还是密文长度问题，都一一消灭。《RSA算法原理（一）》和《RSA算法原理（二）》看了这两篇文章，基本原理也算懂了，可以去看代码的实现过程。
代码如下：
工具类：
package RSA;测试类：
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;
import org.apache.commons.codec.binary.Base64;
public class RSABlock {
/**
* 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;
/**
* <p>
* 生成密钥对(公钥和私钥)
* </p>
*
* @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;
}
/**
* <p>
* 用私钥对信息生成数字签名
* </p>
*
* @param data 已加密数据
* @param 私钥(BASE64编码)
*
* @return
* @throws Exception
*/
public static String sign(byte[] data, String privateKey) throws Exception {
byte[] keyBytes = decryptBASE64(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 encryptBASE64(signature.sign());
}
/**
* <p>
* 校验数字签名
* </p>
*
* @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 = decryptBASE64(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(decryptBASE64(sign));
}
/**
* <P>
* 私钥解密
* </p>
*
* @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 = decryptBASE64(privateKey);
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
/*Cipher cipher = Cipher.getInstance("RSA/ECB/NoPadding"); */
cipher.init(Cipher.DECRYPT_MODE, privateK);
int inputLen = encryptedData.length;
ByteArrayOutputStream out = new ByteArrayOutputStream();
int offSet = 0;
byte[] cache;
int i = 0;
// 对数据分块解密
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;
}
/**
* <p>
* 公钥解密
* </p>
*
* @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 = decryptBASE64(publicKey);
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key publicK = keyFactory.generatePublic(x509KeySpec);
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
/*Cipher cipher = Cipher.getInstance("RSA/ECB/NoPadding");*/
cipher.init(Cipher.DECRYPT_MODE, publicK);
int inputLen = encryptedData.length;
ByteArrayOutputStream out = new ByteArrayOutputStream();
int offSet = 0;
byte[] cache;
int i = 0;
// 对数据分块解密
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;
}
/**
* <p>
* 公钥加密
* </p>
*
* @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 = decryptBASE64(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.ENCRYPT_MODE, publicK);
int inputLen = data.length;
ByteArrayOutputStream out = new ByteArrayOutputStream();
int offSet = 0;
byte[] cache;
int i = 0;
// 对数据分块加密
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;
}
/**
* <p>
* 私钥加密
* </p>
*
* @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 = decryptBASE64(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;
// 对数据分块加密
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;
}
/**
* <p>
* 获取私钥
* </p>
*
* @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 encryptBASE64(key.getEncoded());
}
/**
* <p>
* 获取公钥
* </p>
*
* @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 encryptBASE64(key.getEncoded());
}
/**
* BASE64解码
*
* @param key
* @return
* @throws Exception
*/
public static byte[] decryptBASE64(String key) throws Exception {
return Base64.decodeBase64(key.getBytes());
//return (new BASE64Decoder()).decodeBuffer(key);
}
/**
* BASE64加密
*
* @param key
* @return
* @throws Exception
*/
public static String encryptBASE64(byte[] key) throws Exception {
return new String(Base64.encodeBase64(key));
//return (new BASE64Encoder()).encodeBuffer(key);
}
}
package RSA;
import java.util.Map;
public class RSABlockTest {
static String publicKey;
static String privateKey;
static {
try {
/*Map<String, Object> keyMap = RSABlock.genKeyPair();
publicKey = RSABlock.getPublicKey(keyMap);
privateKey = RSABlock.getPrivateKey(keyMap);*/
publicKey = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDsRajSERYUXn/t5N2ZB/5kH4Duu0aG9kigYIW76nGauOGytwJ5IWG2uV9+52Lj8YZtKNPMMF6je3acA4Q4waT57owKqb4Q0s7AvsACEG6VzqpUhgD66xbrbnejnGwvL1dxU3p4ZXOhh+sws6weoUKqjDRWT574fWHMvZkWZjsAhwIDAQAB";
privateKey = "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";
System.err.println("公钥：" + publicKey);
System.err.println("私钥：" + privateKey);
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) throws Exception {
test();
}
static void test() throws Exception {
String source = "源数据";
System.out.println("加密前：" + source);
//加密
byte[] encodedData = RSABlock.encryptByPublicKey(data, publicKey);
System.out.println("密文：" +encodedData);
//解密
byte[] decodedData = RSABlock.decryptByPrivateKey(encodedData, privateKey);
System.out.println("解密后：" + new String(decodedData););
}
}
非对称算法RSA是私钥加密公钥解密和公钥加密私钥解密两个过程，非对称算法RSA相对于对称算法AES来说相对安全一些，思考安全这块的时候，越是研究的时候，越是感觉没有绝对的安全，安全是相对的，下一篇讲述RSA前台加密后台解密，敬请期待。
参考网址：
http://www.2cto.com/kf/201303/196737.html
https://zhidao.baidu.com/question/714943193692821325.html
http://jin8000608172.iteye.com/blog/1776828
http://blog.csdn.net/greenqingqingws/article/details/51745571
http://www.justabug.net/door-1-rsa/
http://www.bm8.com.cn/webtool/rsa/
http://www.apihome.cn/api/java/Cipher.html
http://blog.csdn.net/songxiaobing/article/details/17505237
http://blog.csdn.net/saindy5828/article/details/45827419
http://www.cnblogs.com/zhaobl/p/4735704.html
http://snowolf.iteye.com/blog/381767
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