Java RSA加密解密

该工具类中用到了BASE64，需要借助第三方类库：javabase64-1.3.1.jar

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*..)

RSAUtils.java


package security;




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;




/**


* <p>


* RSA公钥/私钥/签名工具包


* </p>


* <p>


* 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）


* </p>


* <p>


* 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<br/>


* 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，<br/>


* 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


* </p>


*


* @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;




/**


* <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 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());


}




/**


* <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 = 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));


}




/**


* <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 = 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;


}




/**


* <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 = 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;


}




/**


* <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 = 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;


}




/**


* <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 = 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;


}




/**


* <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 Base64Utils.encode(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 Base64Utils.encode(key.getEncoded());


}




}



Base64Utils.java


package security;




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 it.sauronsoftware.base64.Base64;




/**


* <p>


* BASE64编码解码工具包


* </p>


* <p>


* 依赖javabase64-1.3.1.jar


* </p>


*


*
@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;





/**


* <p>


* BASE64字符串解码为二进制数据


* </p>


*


*
@param base64


*
@return


*
@throws Exception



*/



public
static byte[] decode(String base64)
throws Exception
{



return Base64.decode(base64.getBytes());


}





/**


* <p>


* 二进制数据编码为BASE64字符串


* </p>


*


*
@param bytes


*
@return


*
@throws Exception



*/



public
static String encode(byte[] bytes)
throws Exception
{



return
new String(Base64.encode(bytes));


}





/**


* <p>


* 将文件编码为BASE64字符串


* </p>


* <p>


* 大文件慎用，可能会导致内存溢出


* </p>


*


*
@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);


}





/**


* <p>


* BASE64字符串转回文件


* </p>


*


*
@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);


}





/**


* <p>


* 文件转换为二进制数组


* </p>


*


*
@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;


}





/**


* <p>


* 二进制数据写文件


* </p>


*


*
@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();


}






}



RSATester.java


package security;




import java.util.Map;




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);


}




}