java RSA加密解密实现

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

下载地址：http://download.csdn.net/detail/centralperk/5025595

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：

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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

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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

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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

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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);

}

}