使用jce进行非对称的加密，不需要证书

package util;
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;

import org.apache.commons.codec.binary.Base64;

public class RSAUtil {
	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";
    
    public final static String CONTENT_TYPE = "UTF-8";

    /**
     * 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 signByPrivate(byte[] data, String privateKey) throws Exception {   
        // 解密由base64编码的私钥   
        byte[] keyBytes = Base64.decodeBase64(privateKey.getBytes(CONTENT_TYPE));   

        // 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);   
        String signString = new String(Base64.encodeBase64(signature.sign()));
        return signString;
    }   

    /** 
     * 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 verifyByPublicKey(byte[] data, String publicKey, String sign)   
            throws Exception {   

        // 解密由base64编码的公钥   
        byte[] keyBytes = Base64.decodeBase64(publicKey.getBytes(CONTENT_TYPE));   

        // 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(Base64.decodeBase64(sign.getBytes()));   
    }   

    /** 
     * 解密
     * 用私钥解密 
     *   
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static String decryptByPrivateKey(String data, String key)   
            throws Exception {   
        // 对密钥解密   
        byte[] keyBytes = Base64.decodeBase64(key.getBytes(CONTENT_TYPE));   

        ByteArrayOutputStream writer = new ByteArrayOutputStream();
        // 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);
        String [] dateStr = new String(Base64.decodeBase64(data.getBytes(CONTENT_TYPE))).split("~~");
        for(int i = 0;i < dateStr.length; i ++){
        	writer.write(cipher.doFinal(hexStrToBytes(dateStr[i])));
        }        

        return new String(writer.toByteArray(), "utf-8");   
    }   

    /**  
     * 解密<br> 
     * 用公钥解密 
     *   
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static String decryptByPublicKey(String data, String key)   
            throws Exception {   
        // 对密钥解密   
        byte[] keyBytes = Base64.decodeBase64(key.getBytes(CONTENT_TYPE));
        ByteArrayOutputStream writer = new ByteArrayOutputStream();
        // 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);
        String [] dateStr = new String(Base64.decodeBase64(data.getBytes(CONTENT_TYPE))).split("~~");
        for(int i = 0;i < dateStr.length; i ++){
        	writer.write(cipher.doFinal(hexStrToBytes(dateStr[i])));
        }        

        return new String(writer.toByteArray(), CONTENT_TYPE);   
    }   

    /** 
     * 加密<br> 
     * 用公钥加密 
     *   
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static String encryptByPublicKey(byte[] data, String key)   
            throws Exception {   
        // 对公钥解密   
        byte[] keyBytes = Base64.decodeBase64(key.getBytes(CONTENT_TYPE));   

        // 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);   
        StringBuffer priString = new StringBuffer();
        byte[] priTemp = new byte[64];
        for(int i = 0,x = 0; i <data.length;i++,x++){
        	if(x == 64){
        		priString.append(bytesToHexStr(cipher.doFinal(priTemp))).append("~~");
        		x = 0;
        		priTemp = new byte[64];
        	}
        	priTemp[x] = data[i];
        	if(i+1 == data.length){
        		priString.append(bytesToHexStr(cipher.doFinal(priTemp))).append("~~");
        	}
        }
        return new String(Base64.encodeBase64(priString.toString().getBytes(CONTENT_TYPE)));   
    }   

    /** 
     * 加密<br> 
     * 用私钥加密 
     *   
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static String encryptByPrivateKey(byte[] data, String key)   
            throws Exception {
        // 对密钥解密   
        byte[] keyBytes = Base64.decodeBase64(key.getBytes(CONTENT_TYPE));
        
        // 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);
        StringBuffer priString = new StringBuffer();
        byte[] priTemp = new byte[64];
        for(int i = 0,x = 0; i <data.length;i++,x++){
        	if(x == 64){
        		priString.append(bytesToHexStr(cipher.doFinal(priTemp))).append("~~");
        		x = 0;
        		priTemp = new byte[64];
        	}
        	priTemp[x] = data[i];
        	if(i+1 == data.length){
        		priString.append(bytesToHexStr(cipher.doFinal(priTemp))).append("~~");
        	}
        }
        
        
        return new String(Base64.encodeBase64(priString.toString().getBytes(CONTENT_TYPE)));  
    }

    /** 
     * 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 new String(Base64.encodeBase64(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 new String(Base64.encodeBase64(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 String bytesToString(byte[] encrytpByte) {
    	  String result = "";
    	  for (Byte bytes : encrytpByte) {
    		  result += bytes.toString() + " ";
    	  }
    	  return result;
    }
    
    /*
	 * 将16进制字符串转换为字符数组
	 */
	public static byte[] hexStrToBytes(String s)
	{
		byte[] bytes;

		bytes = new byte[s.length() / 2];

		for (int i = 0; i < bytes.length; i++)
		{
			bytes[i] = (byte) Integer.parseInt(s.substring(2 * i, 2 * i + 2), 16);
		}

		return bytes;
	}

	/*
	* 将字符数组转换为16进制字符串
	*/
	public static String bytesToHexStr(byte[] bcd)
	{
		StringBuffer s = new StringBuffer(bcd.length * 2);

		for (int i = 0; i < bcd.length; i++)
		{
			s.append(bcdLookup[(bcd[i] >>> 4) & 0x0f]);
			s.append(bcdLookup[bcd[i] & 0x0f]);
		}

		return s.toString();
	}
	
	private static final char[] bcdLookup =
	{ '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };


}