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--RSA公钥/私钥/签名工具包

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
     
       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
      
        keyMap = new HashMap
       
        (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
        
          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
         
           keyMap)            throws Exception {        Key key = (Key) keyMap.get(PUBLIC_KEY);        return Base64Utils.encode(key.getEncoded());    }}
         
        
       
      
     

 

Base64Utils.java--BASE64编码解码工具包

package com.ljq.test;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;/** * 
 * BASE64编码解码工具包 * 
 * 
 * 依赖javabase64-1.3.1.jar * 
 *  * @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;    /**     * 
     * BASE64字符串解码为二进制数据     * 
     *      * @param base64     * @return     * @throws Exception     */    public static byte[] decode(String base64) throws Exception {        return Base64.decode(base64.getBytes());    }    /**     * 
     * 二进制数据编码为BASE64字符串     * 
     *      * @param bytes     * @return     * @throws Exception     */    public static String encode(byte[] bytes) throws Exception {        return new String(Base64.encode(bytes));    }    /**     * 
     * 将文件编码为BASE64字符串     * 
     * 
     * 大文件慎用，可能会导致内存溢出     * 
     *      * @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);    }    /**     * 
     * BASE64字符串转回文件     * 
     *      * @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);    }    /**     * 
     * 文件转换为二进制数组     * 
     *      * @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;    }    /**     * 
     * 二进制数据写文件     * 
     *      * @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

package com.ljq.test;import java.util.Map;public class RSATester {    static String publicKey;    static String privateKey;    static {        try {            Map
     
       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();        testHttpSign();    }    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);    }        static void testHttpSign() throws Exception {        String param = "id=1&name=张三";        byte[] encodedData = RSAUtils.encryptByPrivateKey(param.getBytes(), privateKey);        System.out.println("加密后：" + encodedData);                byte[] decodedData = RSAUtils.decryptByPublicKey(encodedData, publicKey);        System.out.println("解密后：" + new String(decodedData));                String sign = RSAUtils.sign(encodedData, privateKey);        System.err.println("签名：" + sign);                boolean status = RSAUtils.verify(encodedData, publicKey, sign);        System.err.println("签名验证结果：" + status);    }        }