RSA加密

本文出处：http://blog.csdn.net/centralperk/article/details/8538697

RSA加密，真是被搞死了。之前做了一个，没有分段。后来在应用中，如果需要加密的字符串太长则会报错。后来发现要采取分段加密。

现在分享一下我在网上找的例子。

有几点需要注意：

1、Cipher 的模式

2、公钥、私钥和加密解密要对应。可以公钥加密、私钥解密，也可以私钥加密、公钥解密。

3、注意字符串的编码，例如：用Base64编码密钥，在加密时要先Base64解码密钥。

4、加签模式要和后台一致

RSAUtils.java

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 
　　　* 这个一定要搞清楚，前台后台要一致
     */  
    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

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  测试类

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: 

" + publicKey);  
            System.err.println("私钥： 

" + 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("
加密前文字：
" + source);  
        byte[] data = source.getBytes();  
        byte[] encodedData = RSAUtils.encryptByPublicKey(data, publicKey);  
        System.out.println("加密后文字：
" + new String(encodedData));  
        byte[] decodedData = RSAUtils.decryptByPrivateKey(encodedData, privateKey);  
        String target = new String(decodedData);  
        System.out.println("解密后文字: 
" + 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：
" + source);  
        byte[] data = source.getBytes();  
        byte[] encodedData = RSAUtils.encryptByPrivateKey(data, privateKey);  
        System.out.println("加密后：
" + new String(encodedData));  
        byte[] decodedData = RSAUtils.decryptByPublicKey(encodedData, publicKey);  
        String target = new String(decodedData);  
        System.out.println("解密后: 
" + 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:
" + sign);  
        boolean status = RSAUtils.verify(encodedData, publicKey, sign);  
        System.err.println("验证结果:
" + status);  
    }  
      
}