原文：http://gaofulai1988.iteye.com/blog/2262802

 

import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;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.SecureRandom;import java.security.Signature;import java.security.spec.PKCS8EncodedKeySpec;import java.security.spec.X509EncodedKeySpec;import javax.crypto.Cipher;import sun.misc.BASE64Decoder;import sun.misc.BASE64Encoder;/** * RSA加密，支持分片加密 * 
 * BCD码（Binary-Coded Decimal‎）亦称二进码十进数或二-十进制代码。 * 用4位二进制数来表示1位十进制数中的0~9这10个数码。 * 是一种二进制的数字编码形式，用二进制编码的十进制代码。 * 注：日常所说的BCD码大都是指8421BCD码形式 * @author Ming *  */public class RSAUtil {    /** 指定加密算法为RSA */    private static String ALGORITHM = "RSA";    /** 指定key的大小 */    private static int KEYSIZE = 1024;    /** 指定公钥存放文件 */    private static String PUBLIC_KEY_FILE = "d:/PublicKey";    /** 指定私钥存放文件 */    private static String PRIVATE_KEY_FILE = "d:/PrivateKey";    public static final String KEY_ALGORITHM = "RSA";    /** 自定义一个串 */    public static final String SIGNATURE_ALGORITHM = "shihaiming@#!RSA";    /**     * 生成密钥对     */    public static void generateKeyPair() throws Exception {        if (getpublickey() == null || getprivatekey() == null) {            /** RSA算法要求有一个可信任的随机数源 */            SecureRandom sr = new SecureRandom();            /** 为RSA算法创建一个KeyPairGenerator对象 */            KeyPairGenerator kpg = KeyPairGenerator.getInstance(ALGORITHM);            /** 利用上面的随机数据源初始化这个KeyPairGenerator对象 */            kpg.initialize(KEYSIZE, sr);            /** 生成密匙对 */            KeyPair kp = kpg.generateKeyPair();            /** 得到公钥 */            Key publicKey = kp.getPublic();            /** 得到私钥 */            Key privateKey = kp.getPrivate();            /** 用对象流将生成的密钥写入文件 */            ObjectOutputStream oos1 = new ObjectOutputStream(new FileOutputStream(PUBLIC_KEY_FILE));            ObjectOutputStream oos2 = new ObjectOutputStream(new FileOutputStream(PRIVATE_KEY_FILE));            oos1.writeObject(publicKey);            oos2.writeObject(privateKey);            /** 清空缓存，关闭文件输出流 */            oos1.close();            oos2.close();        }    }    /**     * 产生签名     *      * @param data     * @param privateKey     * @return     * @throws Exception     */    public static String sign(byte[] data, String privateKey) throws Exception {        // 解密由base64编码的私钥        byte[] keyBytes = decryptBASE64(privateKey);        // 构造PKCS8EncodedKeySpec对象        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);        // KEY_ALGORITHM 指定的加密算法        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);        // 取私钥对象        PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);        // 用私钥对信息生成数字签名        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);        signature.initSign(priKey);        signature.update(data);        return encryptBASE64(signature.sign());    }    /**     * 验证签名     *      * @param data     * @param publicKey     * @param sign     * @return     * @throws Exception     */    public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {        // 解密由base64编码的公钥        byte[] keyBytes = decryptBASE64(publicKey);        // 构造X509EncodedKeySpec对象        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);        // KEY_ALGORITHM 指定的加密算法        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);        // 取公钥对象        PublicKey pubKey = keyFactory.generatePublic(keySpec);        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);        signature.initVerify(pubKey);        signature.update(data);        // 验证签名是否有效        return signature.verify(decryptBASE64(sign));    }    /**     * BASE64解密     *      * @param key     * @return     * @throws Exception     */    public static byte[] decryptBASE64(String key) throws Exception {        return (new BASE64Decoder()).decodeBuffer(key);    }    /**     * BASE64加密     *      * @param key     * @return     * @throws Exception     */    public static String encryptBASE64(byte[] key) throws Exception {        return (new BASE64Encoder()).encodeBuffer(key);    }    /**     * 加密方法 source： 源数据     */    public static String encrypt(String source) throws Exception {        /** 将文件中的公钥对象读出 */        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE));        Key key = (Key) ois.readObject();        ois.close();        /** 得到Cipher对象来实现对源数据的RSA加密 */        Cipher cipher = Cipher.getInstance(ALGORITHM);        cipher.init(Cipher.ENCRYPT_MODE, key);        int MaxBlockSize = KEYSIZE / 8;        int len = (MaxBlockSize - 11) / 8;        String[] datas = splitString(source, len);        StringBuffer mi = new StringBuffer();        for (String s : datas) {            mi.append(bcd2Str(cipher.doFinal(s.getBytes())));        }        return mi.toString();    }    /**     * 字符串分片     *      * @param string     *            源字符串     * @param len     *            单片的长度（keysize/8）     * @return     */    public static String[] splitString(String string, int len) {        int x = string.length() / len;        int y = string.length() % len;        int z = 0;        if (y != 0) {            z = 1;        }        String[] strings = new String[x + z];        String str = "";        for (int i = 0; i < x + z; i++) {            if (i == x + z - 1 && y != 0) {                str = string.substring(i * len, i * len + y);            } else {                str = string.substring(i * len, i * len + len);            }            strings[i] = str;        }        return strings;    }    /**     * bcd 转 Str     *      * @param bytes     * @return     */    public static String bcd2Str(byte[] bytes) {        char temp[] = new char[bytes.length * 2], val;        for (int i = 0; i < bytes.length; i++) {            val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f);            temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0');            val = (char) (bytes[i] & 0x0f);            temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0');        }        return new String(temp);    }    /**     * 解密     *      * @param cryptograph     *            :密文     * @return 解密后的明文     * @throws Exception     */    public static String decrypt(String cryptograph) throws Exception {        /** 将文件中的私钥对象读出 */        @SuppressWarnings("resource")        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE));        Key key = (Key) ois.readObject();        /** 得到Cipher对象对已用公钥加密的数据进行RSA解密 */        Cipher cipher = Cipher.getInstance(ALGORITHM);        cipher.init(Cipher.DECRYPT_MODE, key);        int key_len = KEYSIZE / 8;        byte[] bytes = cryptograph.getBytes();        byte[] bcd = ASCII2BCD(bytes, bytes.length);        StringBuffer sBuffer = new StringBuffer();        byte[][] arrays = splitArray(bcd, key_len);        for (byte[] arr : arrays) {            sBuffer.append(new String(cipher.doFinal(arr)));        }        return sBuffer.toString();    }    /**     * ASCII 转 BCD     *      * @param ascii     * @param asc_len     * @return     */    public static byte[] ASCII2BCD(byte[] ascii, int asc_len) {        byte[] bcd = new byte[asc_len / 2];        int j = 0;        for (int i = 0; i < (asc_len + 1) / 2; i++) {            bcd[i] = asc2bcd(ascii[j++]);            bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc2bcd(ascii[j++])) + (bcd[i] << 4));        }        return bcd;    }    /**     * asc转bcd     *      * @param asc     * @return     */    public static byte asc2bcd(byte asc) {        byte bcd;        if ((asc >= '0') && (asc <= '9'))            bcd = (byte) (asc - '0');        else if ((asc >= 'A') && (asc <= 'F'))            bcd = (byte) (asc - 'A' + 10);        else if ((asc >= 'a') && (asc <= 'f'))            bcd = (byte) (asc - 'a' + 10);        else            bcd = (byte) (asc - 48);        return bcd;    }    /**     * 字节数组分片     *      * @param data     * @param len     * @return     */    public static byte[][] splitArray(byte[] data, int len) {        int x = data.length / len;        int y = data.length % len;        int z = 0;        if (y != 0) {            z = 1;        }        byte[][] arrays = new byte[x + z][];        byte[] arr;        for (int i = 0; i < x + z; i++) {            arr = new byte[len];            if (i == x + z - 1 && y != 0) {                System.arraycopy(data, i * len, arr, 0, y);            } else {                System.arraycopy(data, i * len, arr, 0, len);            }            arrays[i] = arr;        }        return arrays;    }    /** 将文件中的公钥对象读出 */    public static String getpublickey() {        try {            @SuppressWarnings("resource")            ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE));            Key key = (Key) ois.readObject();            String publickey = encryptBASE64(key.getEncoded());            return publickey;        } catch (Exception e) {            e.printStackTrace();        }        return null;    }    /** 将文件中的私钥对象读出 */    public static String getprivatekey() {        try {            @SuppressWarnings("resource")            ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE));            Key key = (Key) ois.readObject();            String privatekey = encryptBASE64(key.getEncoded());            return privatekey;        } catch (Exception e) {            e.printStackTrace();        }        return null;    }    public static void main(String[] args) {        try {            //生成公钥、私钥文件//            generateKeyPair();                        String s = encrypt("https://www.baidu.com/s?ie=utf-8&f=8&rsv_bp=1&rsv_idx=1&ch=3");            System.out.println("加密："+s);            System.out.println("解密："+decrypt(s));            //再用base64加解密            String a = encryptBASE64(s.getBytes());            System.out.println(a);            String b = new String(decryptBASE64(a));            System.out.println(b);            System.out.println("解密b："+decrypt(b));        } catch (Exception e) {            e.printStackTrace();        }    }}