java 加密算法的代码实现

      package rsa;
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;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;
/** 
* RSA安全编码组件 
*   
* @version 1.0 
* @since 1.0 
*/ 
public  class RSACoder  {   
    public static final String KEY_ALGORITHM = "RSA";   
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";   

    private static final String PUBLIC_KEY = "RSAPublicKey";   
    private static final String PRIVATE_KEY = "RSAPrivateKey";   

    /** *//** 
     * 用私钥对信息生成数字签名 
     *   
     * @param data 
     *            加密数据 
     * @param privateKey 
     *            私钥 
     *   
     * @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);   

        // 取私钥匙对象   
        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());   
    }   

    /** *//** 
     * 校验数字签名 
     *   
     * @param data 
     *            加密数据 
     * @param publicKey 
     *            公钥 
     * @param sign 
     *            数字签名 
     *   
     * @return 校验成功返回true 失败返回false 
     * @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);   
        // 取公钥匙对象   
        PublicKey pubKey = keyFactory.generatePublic(keySpec);   

        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);   
        signature.initVerify(pubKey);   
        signature.update(data);   

        // 验证签名是否正常   
        return signature.verify(decryptBASE64(sign));   
    }   

    /** *//** 
     * 解密<br> 
* 用私钥解密 http://www.5a520.cn http://www.feng123.com
     *   
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static byte[] decryptByPrivateKey(byte[] data, String key)   
            throws Exception {   
        // 对密钥解密   
        byte[] keyBytes = decryptBASE64(key);   

        // 取得私钥   
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);   
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);   
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);   

        // 对数据解密   
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());   
        cipher.init(Cipher.DECRYPT_MODE, privateKey);   

        return cipher.doFinal(data);   
    }   

    /** *//** 
     * 解密<br> 
     * 用私钥解密 
     *   
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static byte[] decryptByPublicKey(byte[] data, String key)   
            throws Exception {   
        // 对密钥解密   
        byte[] keyBytes = decryptBASE64(key);   

        // 取得公钥   
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);   
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);   
        Key publicKey = keyFactory.generatePublic(x509KeySpec);   

        // 对数据解密   
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());   
        cipher.init(Cipher.DECRYPT_MODE, publicKey);   

        return cipher.doFinal(data);   
    }   

    /** *//** 
     * 加密<br> 
     * 用公钥加密 
     *   
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static byte[] encryptByPublicKey(byte[] data, String key)   
            throws Exception {   
        // 对公钥解密   
        byte[] keyBytes = decryptBASE64(key);   
        // 取得公钥   
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);   
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);   
        Key publicKey = keyFactory.generatePublic(x509KeySpec);   

        // 对数据加密   
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());   
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);   

        return cipher.doFinal(data);   
    }   

    /** *//** 
     * 加密<br> 
     * 用私钥加密 
     *   
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static byte[] encryptByPrivateKey(byte[] data, String key)   
            throws Exception {   
        // 对密钥解密   
        byte[] keyBytes = decryptBASE64(key);   

        // 取得私钥   
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);   
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);   
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);   

        // 对数据加密   
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());   
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);   

        return cipher.doFinal(data);   
    }   

    /** *//** 
     * 取得私钥 
     *   
     * @param keyMap 
     * @return 
     * @throws Exception 
     */ 
    public static String getPrivateKey(Map<String, Object> keyMap)   
            throws Exception {   
        Key key = (Key) keyMap.get(PRIVATE_KEY);   

        return encryptBASE64(key.getEncoded());   
    }   

    /** *//** 
     * 取得公钥 
     *   
     * @param keyMap 
     * @return 
     * @throws Exception 
     */ 
    public static String getPublicKey(Map<String, Object> keyMap)   
            throws Exception {   
        Key key = (Key) keyMap.get(PUBLIC_KEY);   

        return encryptBASE64(key.getEncoded());   
    }   

    /** *//** 
     * 初始化密钥 
     *   
     * @return 
     * @throws Exception 
     */ 
    public static Map<String, Object> initKey() throws Exception {   
        KeyPairGenerator keyPairGen = KeyPairGenerator   
                .getInstance(KEY_ALGORITHM);   
        keyPairGen.initialize(1024);   
        KeyPair keyPair = keyPairGen.generateKeyPair();   
        // 公钥   
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();   
        // 私钥   
        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;   
    }
    public static byte[] decryptBASE64(String key) throws Exception { 
    	return (new BASE64Decoder()).decodeBuffer(key); 
    	} 

    	/** 
    	* BASE64加密